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The Effects of L-theanine, Caffeine and their Combination on Cognition and Mood

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Abstract

L-Theanine is an amino acid found naturally in tea. Despite the common consumption of L-theanine, predominantly in combination with caffeine in the form of tea, only one study to date has examined the cognitive effects of this substance alone, and none have examined its effects when combined with caffeine. The present randomised, placebo-controlled, double-blind, balanced crossover study investigated the acute cognitive and mood effects of L-theanine (250 mg), and caffeine (150 mg), in isolation and in combination. Salivary caffeine levels were co-monitored. L-Theanine increased 'headache' ratings and decreased correct serial seven subtractions. Caffeine led to faster digit vigilance reaction time, improved Rapid Visual Information Processing (RVIP) accuracy and attenuated increases in self-reported 'mental fatigue'. In addition to improving RVIP accuracy and 'mental fatigue' ratings, the combination also led to faster simple reaction time, faster numeric working memory reaction time and improved sentence verification accuracy. 'Headache' and 'tired' ratings were reduced and 'alert' ratings increased. There was also a significant positive caffeine x L-theanine interaction on delayed word recognition reaction time. These results suggest that beverages containing L-theanine and caffeine may have a different pharmacological profile to those containing caffeine alone.

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... Caffeine's impact on performance can vary based on the type of cognitive task and the subject's level of alertness at baseline.Although caffeine is a well-known psychostimulant, additional research is needed to determine how it affects users who use it frequently.It appears that short-to medium-term work and infrequent use are the best uses for caffeine. [24] Modafinil Modafinil, a schedule 5 stimulant used in South Africa for narcolepsy-related daytime sleepiness, enhances wakefulness. Its mode of action is unclear, but it impacts various brain pathways, possibly boosting cortical activation. ...
... [26]According to the scant research on alert normal, a 200 mg dose can maximally promote attentiveness, with a peak impact occurring in the fourth hour. Modafinil significantly increased subjective alertness without producing euphoria in a trial examining the effects of 300 mg modafinil, 300 mg caffeine, and 15 mg Damphetamine given in a single dose at 9:OO to normal (non-sleep-deprived) participants [24,27] Since most nations do not record modafinil, it is premature to consider using it regularly to improve alertness.The initial results need to be verified by other research. Regarding effects on real-life performance, there are also no findings at all.With minimal toxicity and no abuse potential, a 200 mg dose would have a noticeable impact on alertness and performance. ...
... In most cases, modafinil is a better option than amphetamine when seeking increased alertness, according to the evidence that is currently available. [17,24] Methylphenidate ...
Article
This review paper explores the multifaceted concept of alertness, encompassing its diverse meanings, connections with wakefulness, general mechanisms of action of alertness-producing drugs. Alertness spans a continuum from heightened vigilance to a state of overall readiness, and its nuanced interpretations are examined across various disciplines, neurobiology. The paper critically analyzes the existing literature on alertness-producing drugs, ranging from traditional stimulants like caffeine to modern pharmaceuticals like modafinil. The mechanisms of action, efficacy, and potential side effects associated with these drugs are scrutinized. Additionally, natural compounds and herbal remedies acknowledged for their impact on alertness are explored. The review delves into the interplay between alertness and wakefulness, shedding light on their connections and distinctions. By synthesizing knowledge from theoretical frameworks to practical applications, this review serves as a comprehensive resource for researcher and individuals interested in the multifaceted nature of alertness and the pharmacological tools available for its modulation
... In the case of incorrect responses, subsequent responses were scored as correct if they were correct in relation to the new number. The tasks were scored for the number of correct responses, the number of total attempts, and the percentage of correct responses (correct responses/total responses X 100) [11,45,46]. (2) Continuous Performance Task (CPT)-Participants monitored a continuous series of letters (A-Z; Tahoma Regular font, size 20 point) presented on the screen for 1000 ms and were asked to respond to the detection of the letter "X" only when preceded by the letter "A" by tapping on the screen or pressing the "Space" key. ...
... The participants used the same modality for all tests over the course of the study. A total of 48 correct targets were randomly presented over the course of two minutes, and the task was scored for the percentage of target strings correctly detected, errors of omission (missed targets), false alarms (key pressed/screen tapped when no target presented), and the average reaction time for correct decisions [10,11,45,46]. (3) Rapid-Visual Input Processing Task (RVIP)-Participants were required to monitor a continuous series of digits (1-9; Tahoma Regular font, size 20 point) presented on the screen every 1000 ms. ...
... Of the 480 stimuli presented, there were 8 primary targets, 8 secondary targets, and 48 tertiary targets over the course of the 8 min protocol. The task was scored for the number of correct detections of each target, average reaction time for correct detection of each target, the number of false alarms for each task, and errors of omission (missed targets) [10,11,45,46]. (4) Concentration Task Grid (CGT)-A 100 square grid was used as a measure of concentration. ...
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College students can be sedentary for a majority of the day, which may exacerbate mental health issues or lead to declines in cognitive task performance; however, interventions to address sedentary behaviors may not positively influence everyone. Therefore, the present study sought to identify inter-individual cognitive performance and mood changes of college students during the performance of a cognitive task battery, while seated, standing and with intermittent bouts of walking. Participants (n = 31, age = 25.80 ± 3.61 yrs, 7 male) completed a series of baseline questionnaires including the Trait Mental and Physical Energy and Fatigue survey. Using a randomized controlled cross-over design, participants completed 3 separate testing sessions. At each session, they performed a series of three rounds of cognitive tasks for 27 min and self-reporting mood states for 1 min in the seated position. Each round of cognitive testing was followed by a 2 min break. Each testing day had participants spend the 2 min break in a different condition: sitting, standing, or walking. A series of mixed ANOVAs were used for the primary analysis and a combination of machine learning regressors and classifiers were used for the secondary analysis. Our results suggest that there are unique inter-individual responses to each of the interventions used during the 2 min break. Participants who were low-trait mental and low-trait physical energy benefited the most from the standing desk intervention, while also reporting significant benefits of intermittent walking. However, participants who were low-trait mental fatigue had significant negative consequences of using both standing desks and walking intermittently, while those who were high-trait mental fatigue saw no change in cognitive responses or moods in those conditions. Post hoc machine learning analyses had modest accuracy rates (MAEs < 0.7 for regressors and accuracy rates >60% for classifiers), suggesting that trait mental and physical energy and fatigue may predict inter-individual responses to these interventions. Incorporating standing desks into college classroom settings may result in some students receiving cognitive benefits when inter-individual variability in mood and cognitive responses are accounted for.
... Acute effects of L-theanine on attention in human subjects have been tested mainly employing behavioral methods [16][17][18][19][20][21][22][23][24], sometimes coupled with concurrent recording of brain activity using EEG [17,21,22,24,25] or functional magnetic resonance imaging (fMRI) [26,27]. The findings of these studies are not uniform, not surprisingly, given the heterogeneity of doses of Ltheanine administered, study designs, and the task paradigms used to test attention. ...
... Attentional demands are likely to be even greater in situations where inhibitory control is needed, and these situations bring forth prefrontal executive control areas into action [31,32]. Only a few placebo-controlled studies on L-theanine however, have tapped into this variety and the hierarchical nature of attentional deployment (Table 1) [18][19][20]23]. In this background, we hypothesized that any suppression of distracter processing and/or mind wandering caused by L-theanine could significantly improve the performance of lowlevel attentional tasks, whereas the relative contribution could be less in complex attentional tasks that require active, higher-order processing of target stimuli. ...
... change-from-baseline) for each dose were performed for each outcome measure, using paired ttests ( Figure 3). This enabled comparison of the present study results with the change-from-baseline data reported in previous studies [16,22,23]. We also compared the change-from-baseline reaction times between placebo and each dose, to control for any placebo effect or acute practice effect (Figure 3). ...
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Background: L-theanine is a non-protein-forming amino acid found in tea. Previous research shows high doses (100-400 mg) of L-theanine enhances attention, mainly by reducing mind wandering and distracter processing. We hypothesized that these indirect mechanisms could significantly improve the performance of low-level attentional tasks, whereas the relative contribution could be less in complex attentional tasks that require active, higher-order processing of target stimuli. Methods: To test this hypothesis, we conducted a double-blind, placebo-controlled, counterbalanced, four-way crossover study in 32 healthy young adults, where we compared the effects of three doses of L-theanine (100, 200 and 400 mg) with a placebo (distilled water), administered before and 50 min after dosing, on three attentional tasks from the Cambridge Neuropsychological Test Automated Battery [viz. Reaction Time (RTI)-visuomotor speed, Rapid Visual Information Processing (RVP)-sustained attention, and Stop Signal Task (SST)-inhibitory control]. Results were analyzed in dose × time repeated measures ANOVA models, with subsequent pairwise comparisons. Results: Active doses significantly improved reaction times in the RTI (100-200 mg) and RVP (200-400 mg) tasks from baseline (p < 0.05), but once controlled for the change-from-baseline caused by placebo, only the RTI simple reaction times showed significant improvements, following 100 mg (Δ = 16.3 ms, p = 0.009) and 200 mg (Δ = 16.9 ms, p = 0.009) of L-theanine. Conclusions: Consistent with our hypothesis, these findings suggest that L-theanine significantly improves attention in simple visuomotor tasks, but not in more complex sustained attention tasks, or executive control tasks that require top-down inhibition of pre-active responses.
... The ED used in this study contained various ingredients beyond caffeine. These included B vitamins, L-tyrosine (a precursor for neurotransmitters potentially enhancing focus and alertness at high doses), (16) and L-theanine, an amino acid found in tea, possibly working synergistically with caffeine to improve cognitive function (17). It is important to note that the effectiveness of these additional ingredients, particularly at the specific dosages used in the ED, requires further investigation. ...
... While limited research suggests potential benefits of L-tyrosine supplementation at high doses (2g-12g) for cognitive function during demanding tasks, (28,23) the optimal dosage and effectiveness within the context of an energy drink remain unclear. The ED also contained 100mg of L-theanine, an amino acid found in tea that may improve cognitive function, potentially through synergistic effects with caffeine at specific dose ranges (100-250 mg theanine and 40-160mg caffeine) (17,23). However, the prevalence of these specific dosages within commercially available energy drinks is often unclear due to limited ingredient disclosure (21). ...
... Changes in eating and drinking habits were frequent both in the general population and in healthcare personnel [80−82] . The consumption of tea has been found to positively influence various aspects of mental health, including reduced anxiety, enhanced cognition, and increased brain function [82,83] . Similarly, coffee has garnered considerable scientific interest regarding its impact on mood and emotions. ...
... Consuming one cup of coffee every four hours has been associated with mood improvement. Additionally, low to moderate doses of caffeine (equivalent to two to five cups of coffee per day) have been shown to reduce anxiety [82,83] . ...
Article
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The consumption of drinks with a high caffeine content is a growing phenomenon not only among young people but also among individuals who work night shifts, including healthcare workers. In young people, the motivations that lead to taking energy drinks are linked to performance in studies and recreational activities. In healthcare workers, the motivations are linked to work performance and the need to maintain a high level of wakefulness during the night. This review analyzes the studies published on the consumption of energy drinks in healthcare personnel and the changes that have occurred in recent years also following the stress caused by the recent pandemic on healthcare.
... Examining keywords and word frequencies reveals how research themes have evolved over time [27]. Tracking productivity metrics across journals, institutions, and collaborations provides insight into patterns of knowledge production [28]. As an increasingly significant nutraceutical compound, Ltheanine is an ideal subject for bibliometric evaluation. ...
... The field of food science interacts with pharmacology to make dietary delivery mechanisms an analytical subject [25], [26]. To ensure safety, toxicology is connected with pharmacology and food science [27], [28]. Interactions across groups of studies underscore the multifaced character of L-theanine research as different professions are involved. ...
... Theanine is an amino acid that is very helpful in decreasing physical and mental stress (Kimura et al. 2007). In synergy with caffeine, theanine helps in improving cognitive functions and in elevating the mood (Haskell et al. 2008). It has a tranquilizing effect, relaxes the brain, and decreases anxiety and stress. ...
... It has a tranquilizing effect, relaxes the brain, and decreases anxiety and stress. A very good source of theanine is tea (Kimura et al. 2007;Haskell et al. 2008;Singh 2016). Thus, amino acids and proteins can play important roles as antistress agents. ...
Chapter
Stress leads to several health complications. Stress results in poor dietary habits and poor dietary habits lead to stress. Thus, stress and diet go hand in hand. Stress, eating behaviors, diet, addiction to food, and dietary modifications are important concepts associated with the modern lifestyle. The relation of stress with diet is very important and good dietary modifications can help to beat stress. Food has a very significant effect on health and mood, and by eating a good diet, various physical and psychological problems can be countered. Food products like dietary fibers, vitamins, minerals, vegetables, fruits, etc. are very important to maintain good health. The key to long life and stress lies to a great extent in the diet and food we consume along with good eating behavior.
... Furthermore, reduced responses in functional magnetic resonance imaging were maintained by a single dosage of 200 mg/day [67]. In terms of cognitive function, there are studies in the literature that suggest THE may cause performance decrements when administered single [62,68] or have no effect [69,70]. This circumstance indicates that regardless of the population or the application, it will not have a good effect. ...
... Several randomized controlled trials have reported improvements in cognitive performance by examining the acute effects of the CAF and THE combination of different aspects of cognitive functions [68,[70][71][72][73]. The conducted studies and our findings have shown similar results, but it is evident that there is limited information in the literature regarding the sole supplementation of THE and its combined use with CAF. ...
Article
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Purpose Previous studies have investigated the effect of single or combined caffeine (CAF) and L-theanine (THE) intake on attention performance. However, its effect on shooting performance and cognitive performance in a sport is unknown. The aim of this study was to investigate the hypothesis “Does single or combined CAF and THE supplementation have an effect on shooting and cognitive performance in elite curling athletes?.” It is predicted that over the next decade, studies based on nutritional ergogenic supplements in the developing sport of curling will continue to increase, leading to a significant increase in studies examining the effects of CAF and THE supplementation, alone or in combination, on throwing and cognitive performance in elite curling athletes. Methods In this double-blind, randomized controlled crossover study, twenty-two elite national curling athletes (age 20.20 ± 1.61 and sports age 6.20 ± 0.51 years, height 174.10 ± 7.21 cm, BMI 21.80 ± 3.47 kg/m²) were randomly assigned to CAF (6 mg/kg single dose CAF), THE (6 mg/kg single dose THE), CAF*THE (6 mg/kg CAF and 6 mg/kg THE combined) and PLA (400 mg maltodextrin) groups at each of four sessions. 60 minutes after taking the supplement, the athletes were first given the Stroop test and then asked to shoot. Results Our main findings have shown that the performance of athletes in guard (F=3.452, P < .001, ηp² = .842), draw (F=1.647, P < .001, ηp² = .485), and take-out (F=3.121, P < .001, ηp² = .743) shot styles significantly improved when comparing the combined intake of CAF and THE to the PLA. Regarding cognitive performance evaluation through the Stroop test, during the NR task (F=4.743, P = .001, ηp² = .653), the combined intake of CAF and THE significantly improved reaction times compared to the intake of single CAF, THE, or PLA. The best reaction times during the CR and ICR (respectively; F=2.742, P = .004, ηp² = .328; F = 1.632, P < .001, ηp² = .625) tasks were achieved with the combined CAF and THE intake, showing a significant improvement compared to PLA. During the NER (F=2.961, P < .001, ηp² = .741), task, the combined intake of CAF and THE significantly improved error rates compared to the intake of CAF, THE, or PLA single. The best accuracy rates during the CER and ICER (respectively; F=4.127, P < .001, ηp² = .396; F=3.899, P < .001, ηp² = .710) tasks were achieved with the combined CAF and THE intake, leading to a significant reduction in error rates compared to PLA. Based on these findings, it has been demonstrated in this study that the best shooting scores and cognitive performance were achieved, particularly with the combined intake of CAF and THE. Conclusions Based on these findings, it has been demonstrated in this study that the best shooting scores and cognitive performance were achieved, particularly with the combined intake of CAF and THE. The combined use of these supplements has been found to be more effective on shooting and cognitive performance than their single use.
... It has been reported that black tea consumption has a favorable effect on neurocognitive function. The combined caffeine and theanine effect, has been the subject of numerous studies, since both have an influence on neurotransmitter pathways [48]. Caffeine alone is known to have stimulative properties, while theanine has a relaxing effect, promoting calmness and improving cognitive performance [48,49]. ...
... The combined caffeine and theanine effect, has been the subject of numerous studies, since both have an influence on neurotransmitter pathways [48]. Caffeine alone is known to have stimulative properties, while theanine has a relaxing effect, promoting calmness and improving cognitive performance [48,49]. Jang et al. reported that small doses of theanine can partially counteract the effects of caffeine on sleep in rats [50]. ...
Article
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Background: Sleep bruxism (SB) is a common behavior that can result in various clinical consequences on human health. Risk factors for SB include among others emotional stress, anxiety, tobacco smoking, and excessive alcohol consumption. Coffee and black tea are among the most commonly consumed beverages worldwide. This study explores the influence of coffee and black tea consumption on bruxism intensity, as observed in polysomnographic examination. Methods: Polysomnographic examination with simultaneous camera recording was conducted in 106 adult subjects. The results were evaluated according to guidelines set out by the American Academy of Sleep Medicine (AASM). The study group was divided according to habitual stimulant usage, as declared by the participants in a self-reported questionnaire. Four groups were identified: coffee drinkers versus non-drinkers and black tea drinkers versus non-drinkers. Results: The bruxism episode index (BEI) was increased in coffee-drinkers as opposed to non-drinkers (4.59 ± 3.44 vs. 2.87 ± 1.50, p = 0.011). Sleep fragmentation, measured according to the arousal index, was comparable in coffee drinkers and non-drinkers. Electrolyte and lipid levels were similar in coffee drinkers and non-drinkers. Habitual black tea intake did not affect sleep architecture or bruxism intensity. Conclusions: The study showed that habitual coffee consumption is a risk factor for the increased intensity of sleep bruxism. Neither coffee nor tea consumption is related to sleep fragmentation in habitual drinkers. Coffee and tea intake does not affect electrolyte and lipid concentrations. Caution should therefore be recommended in drinking coffee in people with sleep bruxism.
... Caffeine is widely known to improve various components of athletic performance including aerobic, sprint, and resistance training performance [8,9] but has also been shown to improve alertness, as well as several aspects of cognition [8][9][10], including reaction time [8,11,12], attention/ vigilance [13], and memory [10]. Although several studies report positive effects of caffeine on cognition, others report no change or even negative results due to side effects such as anxiety, restlessness, acute increases in blood pressure, and feelings of jitteriness [1,14,15]. In theory, multi-ingredient supplements are designed to enhance performance while mitigating potential unwanted adverse effects synergistically [2,11,12,15]. ...
... For example, it has been reported that ingesting 150 mg of caffeine, in combination with 250 mg L-theanine, can significantly improve reaction time more than 150 mg of caffeine alone or the placebo [14]. Additionally, acute supplementation with Ginseng, a common psychoactive herbal supplement, has been shown to positively affect various measures of cognition [16]. ...
Article
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Background The demands of typical daily activities require a constant level of alertness and attention. Multi-ingredient, caffeine-containing supplements have been shown to improve measures of cognitive performance. As many of these supplements become readily available, efficacy of each should be evaluated. Therefore, the purpose of this study is to examine the effects of the 4D dietary supplement on cognition, reaction time, and reactive agility. Methods Seventeen healthy males (n = 8) and females (n = 9) between the ages of 18–40 years old (22.8 ± 2.9 years; 167.3 ± 9.6 cm; 65.4 ± 10.9 kg) participated in this double-blind, randomized crossover study. Participants completed three baseline reaction time assessments on the Dynavision and one baseline multiple object tracking assessment on the Neurotracker. Participants then consumed the oral multi-ingredient supplement containing 150 mg of caffeine or non-caffeinated placebo, mixed with 24 ounces of water, and rested for 45 minutes. Following the rest period, participants completed an additional three reaction time assessments and one multiple object tracking (MOT) assessment, as well as 6–12 trials of the Y-reactive agility test. Repeated measures ANOVAs were used to evaluate YRA performance and change values for Dynavision RT, Dynavision score, and MOT speed with either 4D dietary supplement or placebo. Results A significant time × supplement interaction was shown for MOT speed (p = .040, d = .543). Change scores in MOT speed were significantly different from zero following 4D (mean: 0.224 au; 95% confidence interval: 0.050 to 0.398 au) but not placebo supplementation (mean: −0.046 au; 95% confidence interval: −0.220 to 0.127 au). No time × supplement interaction was shown for Dynavision RT (p = .056, d = −.499) or Dynavision score (p = .093, d = .434). No differences were shown for YRA scores following supplementation for the right side (p = .241, d = −.295) or left side (p = .378, d = −.220). Conclusion The 4D dietary supplement appears to improve measures of cognition, specifically attention/spatial awareness, but not reaction time or reactive agility. Future research should examine the effects of this supplement with a larger, less heterogeneous sample and/or in conjunction with an exercise intervention.
... Theanine is the secondary metabolite conferring the umami taste of tea infusion and also balances the astringency and bitterness of tea infusion caused by catechins and caffeine (Lin et al., 2022). It has also many health-promoting functions, including neuroprotective effects, enhancement of immune functions, and potential anti-obesity capabilities, among others (Juneja et al., 1999;Haskell et al., 2008;Kakuda et al., 2000;Liu et al., 2009;Lu et al., 2004;Takagi et al., 2010;Zheng et al., 2004). Therefore, theanine content is highly correlated with green tea quality (Lin et al., 2023). ...
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Ethylamine (EA), the precursor of theanine biosynthesis, is synthesized from alanine decarboxylation by alanine decarboxylase (AlaDC) in tea plants. AlaDC evolves from serine decarboxylase (SerDC) through neofunctionalization and has lower catalytic activity. However, lacking structure information hinders the understanding of the evolution of substrate specificity and catalytic activity. In this study, we solved the X-ray crystal structures of AlaDC from Camellia sinensis (CsAlaDC) and SerDC from Arabidopsis thaliana (AtSerDC). Tyr ³⁴¹ of AtSerDC or the corresponding Tyr ³³⁶ of CsAlaDC is essential for their enzymatic activity. Tyr ¹¹¹ of AtSerDC and the corresponding Phe ¹⁰⁶ of CsAlaDC determine their substrate specificity. Both CsAlaDC and AtSerDC have a distinctive zinc finger and have not been identified in any other Group II PLP-dependent amino acid decarboxylases. Based on the structural comparisons, we conducted a mutation screen of CsAlaDC. The results indicated that the mutation of L110F or P114A in the CsAlaDC dimerization interface significantly improved the catalytic activity by 110% and 59%, respectively. Combining a double mutant of CsAlaDC L110F/P114A with theanine synthetase increased theanine production 672% in an in vitro system. This study provides the structural basis for the substrate selectivity and catalytic activity of CsAlaDC and AtSerDC and provides a route to more efficient biosynthesis of theanine.
... Caffeine [29] acts as a stimulant, whereas L-theanine [30] acts as a neural depressant. The tea tree contains both of these compounds, which may interact beneficially in some cases [31], such as enhancing attention during wakefulness. However, it is improbable that matcha, which contains caffeine in quantities that do not affect sleep, and theanine, in amounts lower than those known to improve sleep quality, would enhance sleep. ...
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Although theanine in matcha improves sleep quality and cognitive function, the caffeine in green tea is thought to worsen sleep quality. Therefore, this study investigated the factors behind the observed improvements in subjective sleep quality in matcha. A placebo-controlled randomized double-blind parallel-group study was conducted on healthy Japanese men and women aged 27–64 years. After 4 weeks of consuming 2.7 g of matcha daily (containing 50.3 mg theanine, 301.4 mg catechins, and 71.5 mg caffeine), no significant differences were observed between the control and matcha groups on total sleep time, sleep latency, wake after sleep onset, or sleep efficiency measured by electroencephalography (EEG). However, the sleep questionnaire Oguri–Shirakawa–Azumi Sleep Inventory, the Middle-age and Aged version (OSA-MA), administered immediately after waking showed a trend toward increased satisfaction with sleep time (p < 0.1), and EEG measurements indicated significantly shortened wake-up times after waking with matcha intake (p < 0.05). The Beck Depression Inventory-II scores also tended to decrease (p < 0.1). The continuous intake of matcha may offer improved subjective sleep quality and emotional stability despite not offering significant changes in objective sleep parameters.
... These four substances work together to produce a stimulated response, known as alert relaxation (Nobre et al., 2008). This 'response' from caffeine alone, as in coffee, is a more wired feeling, which consumers associate more with consumption of caffeine products (Haskell et al., 2007). This may account for the differences in self-perceived dependency between tea and coffee consumption found in this study. ...
... Haskell et al. administered 200 mg of L-theanine, and this stimulated the production of alpha waves in resting participants, causing a sensation of relaxation without drowsiness and side effects. [9] We selected a dose of 200 mg orally because our study group included adult patients and we wanted the maximum effectiveness with the safest maximum dose previously used by other researchers. The peak action of oral alprazolam is from 60 to 90 minutes. ...
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Background and Aims Preoperational anxiety affects the outcome of anesthesia and surgery. Benzodiazepines impair psychomotor performance and cause excessive sedation. L-theanine is a unique amino acid found in green tea. It prevents stress, produces anxiolysis, modulates alpha activity, and provides beneficial effects on mental state, including sleep quality. Gamma-aminobutyric acid (GABA) is a non-proteinogenic amino acid and a phytochemical that is the main inhibitory neurotransmitter in the mammalian brain. It is beneficial in anxiety and stress regulation. Hence, alternative premedicants such as L-theanine and GABA will have a widespread appeal and are safer. The primary objective was to study and compare the effects of L-theanine and GABA on preoperative anxiety, sedation, and cognition in patients posted for major elective surgeries. The secondary objective was to study adverse reactions. Material and Methods A total of 168 patients aged between 18 and 55 years, belonging to the American Society of Anesthesiologists physical status class I and II, and satisfying all inclusion criteria were randomly divided into three groups that received either oral L-theanine, oral GABA, or oral alprazolam 0.25 mg. The anxiety score, sedation score, and psychomotor and cognitive performance scores were noted 60 minutes before and after the administration of the drugs. Results Alprazolam produced more sedation than GABA and L-theanine ( P = 0.0001). Psychomotor and cognitive functions improved with L-theanine and GABA ( P = 0.0001) and decreased with alprazolam ( P = 0.0001). Conclusion GABA and L-theanine result in effective preoperative anxiolysis with minimal sedation and improvement of cognitive skills.
... Higher L-Theanine incorporation might diminish circulatory strain, migraines, sickness, gastrointestinal inconvenience, hunger misfortune, unsteadiness, the runs, and troubles concentrating (Haskell et al., 2008;Giesbrecht et al., 2010;Yoto et al., 2012). ...
... As an adenosine antagonist and central nervous system stimulant, caffeine may be the ingredient to attribute these findings towards (20,21), however other ingredients in the MIPS including L-tyrosine (22), alpha-glyceryl phosphoryl choline (alpha-GPC) (23), and Rhodiola rosea (24) have also shown to enhance cognitive properties. Additionally, a single dose of theanine has been shown to improve recognition visual reaction time compared to placebo (21) and work synergistically with caffeine (21,25). ...
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Introduction Multi-ingredient pre-workout supplements (MIPS) are commonly used by individuals looking to enhance exercise performance and augment adaptations to training. However, the efficacy of commercially available MIPS is largely dependent on the ingredient profile, and new formulations should be investigated to determine their effectiveness. Therefore, the purpose of this study was to examine the effects of a commercially available MIPS product on performance during an upper body resistance exercise protocol. Methods Twenty resistance-trained participants (10 men, 10 women) volunteered to complete this double-blind, placebo-controlled, crossover study consisting of 3 visits. Visit 1 consisted of body composition, 1-repetition maximum (1RM) testing, and familiarization. Visits 2 and 3 consisted of supplementation with either MIPS or placebo (PLA) 1 h prior to completion of an upper body resistance exercise workout during which power output, repetitions completed, rating of perceived exertion (RPE), and perceived recovery were recorded. Assessments of reaction time, isometric mid-thigh pull, and perceived levels of focus, energy, fatigue, and “muscle pump” were also completed before supplementation, 1 h after supplementation, and immediately after exercise. Results Statistical analysis revealed significant main effects of trial for reaction time (p < 0.001) and bench press peak power (p = 0.026) indicating better performance during the MIPS trial. Furthermore, total number of repetitions completed significantly increased (p = 0.003) during the MIPS (96.90 ± 21.31 repetitions) trial compared to PLA (89.50 ± 18.37 repetitions). Additionally, overall session RPE was significantly lower (p = 0.002) during the MIPS (7.6 ± 1.2) trial compared to PLA (8.3 ± 0.9). Discussion These findings suggest that acute supplementation with this MIPS improved upper body resistance exercise performance while reducing participant RPE. Further research should investigate the efficacy of chronic supplementation with this MIPS as the acute response provided an ergogenic benefit.
... According to Steptoe et al. (2007), L-theanine reduces blood cortisol levels in response to stress [9,10,11]. Studies examining bipolar disorder and schizophrenia indicate both of these disorders may be caused by glutaminergic dysregulation [12,13]. ...
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L-theanine is an amino-acid found in green tea (Camellia sinensis), a beverage consumed by people all around the world. Its chemical structure is similar to L-glutamic acid. L-theanine acts as an antagonist of AMPA and kainate receptors as well as partial co-agonist of the NMDA receptors. The application may be associated with several health benefits, such as improvements in cognition, reduction of stress and anxiety-like symptoms. Although the dosage of L-theanine in green tea, which is around 20 mg per tea, is not very likely to have meaningful impact on mental health, supplementation of doses 200-400 mg/day has shown some promising advantages.Despite some evidence towards beneficial impact of L-theanine on mental health, longer-term and larger cohort clinical studies are required in order to justify its application for patients suffering from such diseases as anxiety, depression, bipolar disorder, schizophrenia and sleep disorders. What is more, it is more possible to act as a therapy augmentation in particular cases, rather than conventional therapy replacement.
... Данните от проучванията чрез електроенцефалограма (ЕЕГ) показват, че той има директен ефект върху мозъка, като L-теанинът при високи дози значително увеличава активността в алфа-честотната лента [14], което показва, че действа успокояващо, без да предизвиква сънливост. L-теанинът е още по-ефективен, когато се приема заедно с кофеин, а както е известно, и двете съставки се срещат естествено в чая [15]. ...
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В съвременния свят, наред с различните лекарствени продукти, широко разпространение имат и разнообразни хранителни добавки и медицински изделия от растителен и животински произход, които подобряват мозъчната функция, паметта и способността за концентрация. Тяхната употреба се свързва с повишаване нивото на мотивация, на енергията и с по-лесното преодоляване на трудности. В този обзор са описани най-често срещащите се на пазара и използвани естествени средства за подобряване на когнитивните способности на човека. Редица лечебни растения действат стимулиращо на мозъчната дейност. Някои от тях съдържат кофеин и действието им се дължи именно на този пуринов алкалоид, а при други действието се дължи на други групи биологично активни вещества, като моно-, ди- и тритерпени, сапонини, фенолни киселини и флавоноиди. В обзора е систематизирана научната информация, доказваща употребата на тези растения като средства с ноотропно действие. Някои от разгледаните лечебни растения са известни от хилядолетия със стимулиращото си действие, други, като кафето, въобще не се възприемат като лечебни растения, а трети са широко използвани подправки. Ключови думи: когнитивни способности, ноотропни средства, неврони
... The neuroprotective effects of coffee could be explained by the action of the different molecules that make up this beverage, such as caffeine [7][8][9][10], theaflavins, catechins, phenylindanes and CGA. ...
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Chlorogenic acid (CGA), a polyphenol found mainly in coffee and tea, exerts antioxidant, anti-inflammatory and anti-apoptotic effects at the gastrointestinal level. However, although CGA is known to cross the blood–brain barrier (BBB), its effects on the CNS are still unknown. Oligodendrocytes (OLs), the myelin-forming cells in the CNS, are the main target in demyelinating neuroinflammatory diseases such as multiple sclerosis (MS). We evaluated the antioxidant, anti-inflammatory and anti-apoptotic roles of CGA in M03-13, an immortalized human OL cell line. We found that CGA reduces intracellular superoxide ions, mitochondrial reactive oxygen species (ROS) and NADPH oxidases (NOXs) /dual oxidase 2 (DUOX2) protein levels. The stimulation of M03-13 cells with TNFα activates the nuclear factor kappa-light-chain-enhancer of activated B cell (NF-kB) pathway, leading to an increase in superoxide ion, NOXs/DUOX2 and phosphorylated extracellular regulated protein kinase (pERK) levels. In addition, tumor necrosis factor alpha (TNF-α) stimulation induces caspase 8 activation and the cleavage of poly-ADP-ribose polymerase (PARP). All these TNFα-induced effects are reversed by CGA. Furthermore, CGA induces a blockade of proliferation, driving cells to differentiation, resulting in increased mRNA levels of myelin basic protein (MBP) and proteolipid protein (PLP), which are major markers of mature OLs. Overall, these data suggest that dietary supplementation with this polyphenol could play an important beneficial role in autoimmune neuroinflammatory diseases such as MS.
... Provedena byla také řada studií na zdravých dobrovolnících, které zkoumaly účinek L-theaninu, kofeinu a jejich kombinace na náladu a pozornost a další kognitivní funkce. V některých studiích L-theanin zlepšoval kognitivní funkce a působil s kofeinem synergicky (38)(39)(40). V jiné studii se však účinnost kombinace L-theaninu a kofeinu nelišila od placeba a autoři předpokládají, že jejich účinek je opačný a navzájem se vyruší (41). Vliv L-theaninu na kognitivní funkce tedy není zcela jasný. ...
... 30 Green tea contains both components; in some cases, they have a beneficial effect due to their interaction, which is enhanced in the wakefulness state. 32 The significance of these two components regarding sleep is not clear. In this study, we analyzed sleep quality using EEG, cer-ebral blood flow using near-infrared spectroscopy (NIRS), and LF and high-frequency (HF) band power values calculated from the pulse wave (LF/HF) to investigate the interaction between a mixture of theanine and caffeine in promoting sleep onset. ...
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Energy drinks take advantage of caffeine's effects on wakefulness and performance; however, excessive intake has a negative effect on sleep. Green tea is consumed worldwide and has both a stimulating effect from caffeine and a calming or relaxing effect from theanine. Theanine reduces the excitotoxicity of caffeine. This study evaluated whether theanine improves the sleep quality worsened by caffeine in healthy young women. Sleep latency, sleep time, wake after sleep onset (WASO) time, and the number of WASOs were measured. A crossover study was performed using four treatment groups: theanine (50 mg), caffeine (30 mg), combined theanine and caffeine (TC), and placebo. The sleep stage was determined using electroencephalograms, and cerebral blood flow was measured using near-infrared spectroscopy. The caffeine group showed a significant increase in the WASO time compared with the placebo group; no difference was observed between the theanine or TC group and the placebo group. There were no differences in the sleep-onset latency or number of WASOs between the theanine, caffeine, or TC groups and the placebo group. In combination with theanine, only the caffeine-induced increase in the WASO time was suppressed. Our results suggest that theanine can reduce caffeine's effects on sleep quality.
... L-theanine (γ-glutamylethylamide) is a non-protein amino acid biosynthesized in tea plants that contributes to the umami taste of green tea. In addition to its pleasant taste, L-theanine has many beneficial effects to human health, including enhancing anti-tumor activity [70], reducing blood pressure [71], suppressing weight gain and fat accumulation [72,73], improving the immune system [74], displaying neuroprotection [75], inhibiting the negative effects of caffeine [76], and improving concentration and learning ability [77]. L-theanine is mainly biosynthesized in the roots and transferred to the developing leaves via the stem (thorough phloem), where it accumulates [78,79]. ...
Article
Tea (Camellia sinensis), one of the most important beverage crops originated from China and is now cultivated worldwide, provides numerous secondary metabolites that account for its health benefits and rich flavor. However, the lack of an efficient and reliable genetic transformation system has seriously hindered the gene function investigation and precise breeding of C. sinensis. In this study, we established a highly efficient, labor-saving, and cost-effective Agrobacterium rhizogenes-mediated hairy roots genetic transformation system for C. sinensis, which can be used for gene overexpression and genome editing. The established transformation system was simple to operate, bypassing tissue culture and antibiotic screening, and only took two months to complete. We used this system to conduct function analysis of transcription factor CsMYB73 and found that CsMYB73 negatively regulates L-theanine synthesis in tea plant. Additionally, callus formation was successfully induced using transgenic roots, and the transgenic callus exhibited normal chlorophyll production, enabling the study of the corresponding biological functions. Furthermore, this genetic transformation system was effective for multiple C. sinensis varieties and other woody plant species. By overcoming technical obstacles such as low efficiency, long experimental periods, and high costs, this genetic transformation will be a valuable tool for routine gene investigation and precise breeding in tea plants.
... [28] However, there is also research which shows that coffee and tea have other bioactive components such as theanine, polyphenols, theobromine and chlorogenic acid, which could lead to differences in the behavioural effects of these beverages. [30][31][32][33][34][35] Many of the studies of coffee have used soluble or instant coffee, whereas studies of tea have often used tea bags. Little is known about the effects of instant tea, and one of the aims of the present study was to examine the effects of tea made from granules. ...
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Background: Coffee and tea are major sources of caffeine and have
... У клініці L-теанін проявив себе як ефективний протитривожний засіб саме в осіб із тривогою на тлі хронічного стресу. При цьому його анксіолітична дія поєднується з певним розслаблюючим ефектом та м'якою снодійною дією, але без будь-яких ознак седації [15], а також певною прокогнітивною дією [23]. Це свідчить про комплексний нормалізуючий нейротропний ефект цієї амінокислоти природного походження. ...
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The article examines modern approaches to the problem of psychoemotional disorders and, in particular, anxiety syndrome in psychosomatic pathology. Special attention is paid to the somatic «masks» of the anxiety syndrome in the most common clinical forms of psychosomatics, as well as the role of chronic stress in the pathogenesis of the specified syndrome and in the occurrence of neurotransmitter imbalance, which is the basis of the development of anxiety disorders. The advantages and disadvantages of the main groups of drugs used to treat anxiety in patients with various nosological forms of psychosomatic pathology are analyzed. In this regard, special attention is paid to the possibilities of combined phytotherapeutic agents. The advantages of the combination within one dosage form of plant components with proven synergistic anxiolytic action are emphasized. This combination is the original domestic phytotherapeutic agent, which for the first time contains a combination of Vitania extract, L-theanine and Passiflora extract. The peculiarities of the mechanisms of action of each of the components of the specified combination and the justification of the expediency of their combination from the point of view of the impact on the main pathogenetic mechanisms of the development of the anxiety syndrome are considered. Special attention is paid to the issue of safety during therapy with the specified agent as one of the leading criteria for choosing a tool for the treatment of psycho-emotional disorders in psychosomatic pathology. Reasoned expediency of using the considered phytotherapeutic combination in the treatment of various clinical forms of anxiety disorders in general medical practice.
... caffeine may also enhance the apparent performance in working memory tasks without actually influencing the true memory function 7 . Acute caffeine intake was frequently found to shorten the reaction time in working memory performance or improve the overall performance without dissociating the enhanced attention process by caffeine [11][12][13][14] . Interestingly, studies that separated or statistically controlled for caffeine effects on low-order task performance (i.e. using high-against low-workload task to control for low-order processes) often reported no clear-cut net benefits on working or short-term memory function [15][16][17][18][19][20] . ...
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Acute caffeine intake has been found to increase working memory (WM)-related brain activity in healthy adults without improving behavioral performances. The impact of daily caffeine intake—a ritual shared by 80% of the population worldwide—and of its discontinuation on working memory and its neural correlates remained unknown. In this double-blind, randomized, crossover study, we examined working memory functions in 20 young healthy non-smokers (age: 26.4 ± 4.0 years; body mass index: 22.7 ± 1.4 kg/m2; and habitual caffeine intake: 474.1 ± 107.5 mg/day) in a 10-day caffeine (150 mg × 3 times/day), a 10-day placebo (3 times/day), and a withdrawal condition (9-day caffeine followed by 1-day placebo). Throughout the 10th day of each condition, participants performed four times a working memory task (N-Back, comprising 3- and 0-back), and task-related blood-oxygen-level-dependent (BOLD) activity was measured in the last session with functional magnetic resonance imaging. Compared to placebo, participants showed a higher error rate and a longer reaction time in 3- against 0-back trials in the caffeine condition; also, in the withdrawal condition we observed a higher error rate compared to placebo. However, task-related BOLD activity, i.e., an increased attention network and decreased default mode network activity in 3- versus 0-back, did not show significant differences among three conditions. Interestingly, irrespective of 3- or 0-back, BOLD activity was reduced in the right hippocampus in the caffeine condition compared to placebo. Adding to the earlier evidence showing increasing cerebral metabolic demands for WM function after acute caffeine intake, our data suggest that such demands might be impeded over daily intake and therefore result in a worse performance. Finally, the reduced hippocampal activity may reflect caffeine-associated hippocampal grey matter plasticity reported in the previous analysis. The findings of this study reveal an adapted neurocognitive response to daily caffeine exposure and highlight the importance of classifying impacts of caffeine on clinical and healthy populations.
... One study [170] found that a single dose of 50 mg caffeine had its expected effects in terms of improved alertness and increased accuracy on an attention task, but that the combination of caffeine with 100 mg ʟ-theanine resulted in additional benefits in terms of improved attention task performance and improved long-term memory, an outcome not typically associated with caffeine alone. A subsequent study [171] found that whereas caffeine (150 mg) and caffeine combined with ʟ-theanine (250 mg) elicited common improvements in the performance of a rapid visual information processing (RVIP) task and decreased subjective 'mental fatigue', the caffeine/ʟ-theanine combination also led to a number of significant benefits over those seen following caffeine alone, including improved alertness and tiredness and enhanced working memory performance; again, this was an outcome not typically associated with caffeine alone. Similarly, whilst single doses of 200 mg of ʟ-theanine and 160 mg of caffeine improved the performance of one of two attention tasks, their combination resulted in a numerically more significant effect than either treatment alone [172]. ...
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The plant defence compound caffeine is widely consumed as a performance enhancer in a sporting context, with potential benefits expected in both physiological and psychological terms. However, although caffeine modestly but consistently improves alertness and fatigue, its effects on mental performance are largely restricted to improved attention or concentration. It has no consistent effect within other cognitive domains that are important to sporting performance, including working memory, executive function and long-term memory. Although caffeine’s central nervous system effects are often attributed to blockade of the receptors for the inhibitory neuromodulator adenosine, it also inhibits a number of enzymes involved both in neurotransmission and in cellular homeostasis and signal propagation. Furthermore, it modulates the pharmacokinetics of other endogenous and exogenous bioactive molecules, in part via interactions with shared cytochrome P450 enzymes. Caffeine therefore enjoys interactive relationships with a wide range of bioactive medicinal and dietary compounds, potentially broadening, increasing, decreasing, or modulating the time course of their functional effects, or vice versa. This narrative review explores the mechanisms of action and efficacy of caffeine and the potential for combinations of caffeine and other dietary compounds to exert psychological effects in excess of those expected following caffeine alone. The review focusses on, and indeed restricted its untargeted search to, the most commonly consumed sources of caffeine: products derived from caffeine-synthesising plants that give us tea (Camellia sinensis), coffee (Coffea genus), cocoa (Theabroma cacao) and guaraná (Paullinia cupana), plus multi-component energy drinks and shots. This literature suggests relevant benefits to mental performance that exceed those associated with caffeine for multi-ingredient energy drinks/shots and several low-caffeine extracts, including high-flavanol cocoa and guarana. However, there is a general lack of research conducted in such a way as to disentangle the relative contributions of the component parts of these products.
... Furthermore, the amino acid theanine found in tea was found to attenuate memory impairment in mice [53]. Two previous randomized controlled trials revealed that L-theanine combined with caffeine enhanced performance on attention tasks [54,55], with more studies needed to investigate the effect of caffeine in tea on cognitive function in isolation [29]. The cognitive protective effect of tea may be due to the synergistic effect of several of its chemical components rather than a single compound, as it contains various phytochemicals and nutrients, such as vitamin C. ...
Article
Background: Previous studies suggest a positive effect of tea intake on cognition. Additional micronutrients that may moderate this association was not previously examined. Objective: To examine the association between tea consumption and cognition and explore the interaction between tea consumption and iron intake. Methods: Data from the China Health and Nutrition Survey between 1997 and 2011 was used. 4,820 individuals (≥55 years) were included in the analyses. Measurement of cognitive function was conducted in 1997, 2000, 2004, and 2006. Tea consumption was self-reported. Food intake was assessed by 24-hour dietary recalls of three consecutive days during home visits between 1997 and 2011. Multivariable mixed linear regression and logistic regression was used to assess the association. Results: Tea consumption was associated with reduced global cognitive function decline. In fully adjusted models, regression coefficients (95% CIs) for those who consumed 0 cups/day,<2 cups/day, 2-3.9 cups/day, and≥4 cups/day of tea were 0, -0.09 (-0.55-0.37), 0.05 (-0.34-0.45), and 0.87 (0.46-1.29), respectively. This effect was stronger in adults > 60 years. Tea consumption of≥4 cups/day was inversely associated with self-reported poor memory (OR 0.70 (95% CI 0.56-0.86)) and memory decline (OR, 0.73 (95% CI 0.62-0.87)). There was a significant interaction between tea consumption and iron intake in relation to cognition. High iron intake was inversely associated with cognition in non-consumers of tea but not in tea consumers. Conclusion: Higher tea intake is associated with reduced cognitive decline in adults and inhibits the adverse effect of high iron intake.
... Albeit limited, the research evidence hitherto suggests combination of L-theanine with caffeine producing additive or synergistic effects [26,27,32,34,36]. Hence, we believe that incorporating a caffeine arm to future studies may build upon and bring forth further evidence on the combined effects of L-theanine and caffeine. ...
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Tea (Camellia sinensis) is a historically and economically important beverage for Sri Lanka; and is traditionally believed to have relaxing or calming effects. Some evidence attributes these effects to a constituent of tea leaves; L-theanine, a non-protein-forming amino acid structurally similar to glutamic acid. Over the years, research has found L-theanine to also have effects on various cognitive functions, including attention. This review focuses on the research conducted thus far on the acute effects of L-theanine on neurobehavioral, neurophysiological, and functional neuroimaging indices, cognition and attention. Despite the heterogeneity of testing paradigms across studies, experimental evidence increasingly suggests that L-theanine could improve visual selective attention. Contrary to traditional belief, the amount of L-theanine in a cup of tea (4.5-22.5mg) seems to cause no significant effects; and attentional improvement is more prominent with much higher doses (100-500mg). This makes it worth exploring the possibility of enriching tea with L-theanine, while preserving the unique flavour of the product. L-theanine has an additive effect with caffeine in enhancing attention, but unlike caffeine, L-theanine can be ingested in high doses with no risk of adverse effects, tolerance or dependence. The evidence on attentional effects of L-theanine is almost entirely based on healthy samples who have undergone laboratory-based attentional tasks that employed abstract stimuli. When translating these laboratory findings to real-life scenarios, incorporating more real-life-based stimulus paradigms (i.e., simulated driving scenarios) is warranted. The clinical relevance of L-theanine research could also be improved by exploring the effects of L-theanine in cognitively compromised groups of individuals.
... Theanine can not only be used as an additive, but also has a variety of physiological functions, which can directly affect the central nervous system, regulate mood, memory ability and so on. [10][11][12] At the same time, its pharmacological effects have shown that theanine can improve the antioxidant capacity of liver cells and prevent liver damage caused by ethanol. 13 It also has an antitumor and antihypertensive effect, which can reduce the oxidation of low-density lipoprotein and prevent atherosclerosis like theaavins. ...
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The health benefits of drinking tea stem from it being rich in polyphenols and other physiologically-active substances. Thus, exploring the synergistic effect between polyphenols and a variety of physiologically-active substances can contribute to our understanding of how tea benefits health. In this work, we have studied the interactions between catechin and theanine, exploring the synergetic antioxidant mechanism of the two molecules. Electrochemical characterization results showed that the oxidation peak current of catechin decreased gradually with the concentration of theanine, which is due to theanine spontaneously binding to catechin through intermolecular hydrogen bonds and forming molecular clusters via two hydrogen bonds. The binding constant is 4.75 at room temperature. The molecular clusters reduce the diffusion coefficient of catechin in solution, leading to the slow release of its antioxidant capacity (ability to effectively inhibit free radical oxidation reactions). Density functional theory calculations were also performed and verified the binding behavior. In identifying the synergistic effect between catechin and theanine on the antioxidant capacity of tea, this study adds to our understanding of the efficacy of tea polyphenols.
... caffeine may also enhance the apparent performance in working memory tasks without actually influencing the true memory function 7 . Acute caffeine intake was frequently found to shorten the reaction time in working memory performance or improve the overall performance without dissociating the enhanced attention process by caffeine [11][12][13][14] . Interestingly, studies that separated or statistically controlled for caffeine effects on low-order task performance (i.e. using high-against low-workload task to control for low-order processes) often reported no clear-cut net benefits on working or short-term memory function [15][16][17][18][19][20] . ...
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Caffeine has been reported to acutely increase working memory (WM)-related brain activity without a significant enhancement in performances in healthy adults. As a ritual in the society, however, the impacts of daily caffeine intake on WM-related brain activities remain unknown. This double-blind randomized crossover study aimed to investigate the blood-oxygen-level-dependent (BOLD) activity in 20 young healthy non-smokers (age: 26.4 ± 4.0 years; body mass index: 22.7 ± 1.4 kg/m²; and self-report habitual caffeine intake: 474.1 ± 107.5 mg/day) during WM tasks (consisting high and low workloads) after 10-day caffeine intake (150 mg x 3/day) and after 36h withdrawal (9-day caffeine & 1-day placebo) compared to 10-day placebo intake (150 mg x 3/day). In caffeine condition, participants showed more errors and longer reaction times (RTs) in WM tasks, without significant changes in the workload-dependent BOLD activities. Worse WM performance remained after acute withdrawal. Furthermore, independent of workloads, BOLD activity was reduced in hippocampus in caffeine but partially mitigated in withdrawal condition. No significant differences in simple attention tasks were observed between caffeine and placebo, while withdrawal showed longer RTs than the other two. Taken together with the earlier evidence, caffeine might acutely increase the demands of cerebral metabolic activities for WM, which however could no longer be fulfilled after daily intake and results in compromised performances. The reduced hippocampal activities additionally echoed the caffeine-reduced grey matter volume previously reported. This study is funded by Swiss National Science Foundation (grant 320030 − 163058).
... Theanine: Theanine has been studied for its potential ability to reduce mental and physical stress, improve cognition, and boost mood and cognitive performance in a synergistic manner with caffeine (Haskell et al., 2008). ...
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It is generally recognized that there is a relationship between nutrition and immunity or health. From past 20 years onwards, the relationship of immunity with psychological and neurological factors is also becoming clear. In the last 20 years, it has become much clearer that psychological and neurological factors also influence immunity. A healthy diet, not deficient in energy, nutrients and micronutrients is essential to prevent and fight off diseases. Through various researches it can be said that nutrition affects the immune system of our body directly and indirectly. During inflammation, the release of pro-inflammatory cytokines not only leads to activation of immune cells but also to a decrease in appetite and increased catabolism of muscle tissue. In conclusion, there is an intricate relationship between stress, nutrition and immunity.
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Tea seedlings (Camellia sinensis) have well-developed root system with strong taproot and lateral roots. Compared with ordinary cuttings, it has stronger vitality and environmental adapt ability, thus facilitating the promotion of good varieties. However, there is less of detailed research on the rooting and germination process of tea seeds. In this study, matrix-assisted laser desorption ionization time-of-flight mass spectrometry was used to conduct non-targeted spatial mass spectrometry imaging of the main organs during growth of tea seedlings. A total of 1, 234 compounds were identified, which could be classified into 24 classes. Among them, theanine, as the most prominent nitrogen compound, was synthesized rapidly at the early stage of embryo germination, accounting for more than 90% of the total free amino acids in radicle, and then transferred to each meristem region through the mesocolonial sheath, indicating that theanine-based nitrogen flow plays a decisive role in the organ formation during the development of tea seedlings. Nutrients stored in the cotyledon were rapidly hydrolyzed to dextrin and 3-phosphoglyceraldehyde at the early stages of germination, and subsequently converted to other forms that provided carbon and energy for development, such as raffinose and d-galactose (glucose), which were mainly distributed in the growing zones of the root apex and the apical meristems of the stem. This study provides a new perspective on the synthesis and metabolism of substances during the development of tea seedlings and contributes to a better understanding of the biological characteristics of tea varieties.
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Golden camellia is defined as a species of the Camellia genus with yellow flowers, which have long been used as a medicine, food, and cosmetic in many Asian countries. To date, more than 50 golden camellia species are considered endemic in Vietnam; however, more information is needed about its chemical constituents and biological activity. This work aims to unveil the potential of Camellia tienii Ninh, a golden camellia species, as an herbal beverage by examining the presence and abundance of chemical components in flowers and leaves. A comprehensive strategy has been developed using both liquid and gas chromatography coupled with mass spectrometry. Specifically, LC‐MS‐based widely targeted analyses were opted to characterize 158 polar metabolites belonging mainly to flavonoids, catechins, and amino acids classes, and an untargeted approach using GC‐MS annotated 42 major volatile compounds such as terpenes and fatty acids. The extensive profile revealed by these techniques could help understand the significant discrimination between two organs. C. tienii flowers accumulated more flavonoids, amino acids, and fatty acids, while leaves contain more terpenes, suggesting different pharmacological properties of these materials. Overall, this pipeline can be applied for other Camellia species and valorization of these valuable resources for health benefits purposes.
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Background: L-theanine is a non-protein-forming amino acid found in tea. Limited evidence suggests that it improves selective attention. Sleep deprivation impairs attention and psychomotor reactions, affecting automobile driving. We aimed to determine whether L-theanine improves neurobehavioral measures of visual attention in acutely sleep-deprived healthy adults in a traffic-scene-based attention task. Methods: In a double-blind, placebo-controlled, counterbalanced, two-way crossover study, we compared the effects of a 200-mg dose of L-theanine with a placebo (150 ml of distilled water) on a computerised, traffic-scene-based visual recognition reaction task in 24 healthy volunteers (age 20-25 years; 13 males) sleep-deprived overnight. The participants made speeded button-presses to imminent accident scenes (i.e. hits), while ignoring safe scenes. They were tested pre-dose and 45 min post-dose, each treatment administered one week apart. Results: Hit rates were more than 90% in all sessions, and were similar in two treatments, pre- vs post-dose. L-theanine significantly reduced false alarms (i.e. responses to safe scenes) (p = 0.014) and increased A' (i.e. target-distractor discriminability) (p = 0.009), whereas placebo did not (p > 0.05). L-theanine reduced hit reaction time by 38.65 ms (p = 0.007), and placebo by 19.08 ms (p = 0.016), however reaction time changes from baseline were not significantly different between treatments (p > 0.05). Conclusions: L-theanine in high doses appears to improve selective visual attention by concurrently improving information processing speed and target-distractor discriminability in acutely sleep-deprived individuals. This is consistent with previous functional neuroimaging findings, where L-theanine suppressed distractor-processing and default-mode-network activity in visual selective attention tasks.
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The microbiota–gut–brain axis is a promising target to alleviate the growing burden of neurologic and mental health disorders. Dietary polyphenols act on multiple components of the microbiota–gut–brain axis, but this complex relationship requires further attention. This randomized, placebo-controlled, double-blind, crossover trial (ACTRN12622000850774) compared 4 wk of a commercially available flavonoid-rich blackcurrant beverage (FBB; 151 mg anthocyanins, 308 mg total polyphenols) with placebo in 40 healthy females (18–45 y). The primary outcome of stress reactivity was assessed by change in present feelings of stress, mood, and fatigue before and after completing a 20-min cognitive stressor [Purple multitasking framework (MTF)]. Secondary end points included cognitive performance (MTF), mood [profile of mood states (POMS)], sleep (Pittsburgh Sleep Quality Index), fecal microbiome composition and functional potential (shotgun sequencing), and blood biomarker concentrations (brain-derived neurotrophic factor, tryptophan, kynurenine, and interleukin 6). Statistical analyses were conducted on an intention-to-treat basis using linear mixed-effect models. Thirty-eight participants completed both intervention arms. There was no significant treatment effect on the primary outcome of stress reactivity. Compared with placebo, working memory (letter retrieval scores from MTF), and anxiety/tension and anger/hostility domains of the POMS improved with FBB supplementation (time × intervention interaction; P < 0.05). There were no treatment effects on gut microbiome composition or functional potential. Baseline abundances of Bifidobacterium genera and species (Bifidobacterium longum and Bifidobacterium bifidum) tended to be higher in participants with the greatest improvements in letter retrieval scores with FBB supplementation (nominally significant, P < 0.05). In conclusion, 4-wk FBB supplementation improved secondary outcomes of working memory performance during multitasking and mood outcomes in healthy adult females. These results should be confirmed in a larger cohort with a longer duration of follow-up.
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Nootropics are substances that enhance cognition through various mechanisms. Nootropics include various substances, ranging from derivatives of neurotransmitters to naturally occurring plants. They are used therapeutically for certain psychological disorders including Alzheimer’s dementia and mild cognitive impairment. More recently, healthy individuals have been shown to consume nootropics to enhance mental processes above baseline levels. Nootropic modes of action vary, but the most supported mechanisms include increased acetylcholine levels in synapses, increased levels of monoamine oxidases, long-term potentiation through neural modulation of glutamate receptors, and decreased adenosine levels. However, numerous side effects can occur when taking nootropics, including insomnia, dependence, nausea, and anxiety. Nootropics also need to be considered when physicians prescribe them, as some individuals who request these drugs are perfectly healthy. In addition, the effects of nootropics are often misportrayed in popular media, leading individuals to think that these substances will give them a drastic increase in their cognitive ability.
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Intercropping is a widely recognised technique that contributes to agricultural sustainability. While intercropping leguminous green manure offers advantages for soil health and tea plants growth, the impact on the accumulation of theanine and soil nitrogen cycle are largely unknown. The levels of theanine, epigallocatechin gallate and soluble sugar in tea leaves increased by 52.87% and 40.98%, 22.80% and 6.17%, 22.22% and 29.04% in intercropping with soybean–Chinese milk vetch rotation and soybean alone, respectively. Additionally, intercropping significantly increased soil amino acidnitrogen content, enhanced extracellular enzyme activities, particularly β‐glucosidase and N ‐acetyl‐glucosaminidase, as well as soil multifunctionality. Metagenomics analysis revealed that intercropping positively influenced the relative abundances of several potentially beneficial microorganisms, including Burkholderia , Mycolicibacterium and Paraburkholderia . Intercropping resulted in lower expression levels of nitrification genes, reducing soil mineral nitrogen loss and N 2 O emissions. The expression of nrfA/H significantly increased in intercropping with soybean–Chinese milk vetch rotation. Structural equation model analysis demonstrated that the accumulation of theanine in tea leaves was directly influenced by the number of intercropping leguminous green manure species, soil ammonium nitrogen and amino acid nitrogen. In summary, the intercropping strategy, particularly intercropping with soybean–Chinese milk vetch rotation, could be a novel way for theanine accumulation.
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Ethylamine (EA), the precursor of theanine biosynthesis, is synthesized from alanine decarboxylation by Alanine Decarboxylase (AlaDC) in tea plants. AlaDC evolves from Serine Decarboxylase (SerDC) through neofunctionalization and has lower catalytic activity. However, lacking structure information hinders the understanding of the evolution of substrate specificity and catalytic activity. In this study, we solved the X-ray crystal structures of AlaDC from Camellia sinensis (CsAlaDC) and SerDC from Arabidopsis thaliana (AtSerDC). Tyr341 of AtSerDC or the corresponding Tyr336 of CsAlaDC is essential for their enzymatic activity. Tyr111 of AtSerDC and the corresponding Phe106 of CsAlaDC determine their substrate specificity. Both CsAlaDC and AtSerDC have a distinctive zinc finger that contributes to the activity and has not been identified in any other Group II PLP-dependent amino acid decarboxylases. Based on the structure comparison and evolution analysis AlaDC or SerDC led us to perform mutation screen of CsAlaDC. The results indicated that the mutation of L110F or P114A in the CsAlaDC dimerization interface significantly improved the catalytic activity by 110% and 59%, respectively. Combining double mutant CsAlaDCL110F/P114A with theanine synthetase increased 672% of theanine production in an in vitro system. This study provides the structural basis for the substrate selectivity and catalytic activity of CsAlaDC and AtSerDC and sheds light on a new direction for the efficient industrial synthesis of theanine.
Preprint
Ethylamine (EA), the precursor of theanine biosynthesis, is synthesized from alanine decarboxylation by Alanine Decarboxylase (AlaDC) in tea plants. AlaDC evolves from Serine Decarboxylase (SerDC) through neofunctionalization and has lower catalytic activity. However, lacking structure information hinders the understanding of the evolution of substrate specificity and catalytic activity. In this study, we solved the X-ray crystal structures of AlaDC from Camellia sinensis (CsAlaDC) and SerDC from Arabidopsis thaliana (AtSerDC). Tyr341 of AtSerDC or the corresponding Tyr336 of CsAlaDC is essential for their enzymatic activity. Tyr111 of AtSerDC and the corresponding Phe106 of CsAlaDC determine their substrate specificity. Both CsAlaDC and AtSerDC have a distinctive zinc finger that contributes to the activity and has not been identified in any other Group II PLP-dependent amino acid decarboxylases. Based on the structure comparison and evolution analysis AlaDC or SerDC led us to perform mutation screen of CsAlaDC. The results indicated that the mutation of L110F or P114A in the CsAlaDC dimerization interface significantly improved the catalytic activity by 110% and 59%, respectively. Combining double mutant CsAlaDCL110F/P114A with theanine synthetase increased 672% of theanine production in an in vitro system. This study provides the structural basis for the substrate selectivity and catalytic activity of CsAlaDC and AtSerDC and sheds light on a new direction for the efficient industrial synthesis of theanine.
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Tea processed from albino/etiolated tea shoots is favored by consumers because of its high theanine accumulation. To explore why theanine accumulates highly in new shoots of albino/etiolated tea cultivars, we compared theanine content in shoots and roots of albino/etiolated and common green tea cultivars. Results suggested that high theanine accumulation in albino/etiolated tea shoots was likely not caused by higher theanine biosynthesis in roots. Further analyses suggested that CsAlaDC-catalyzed ethylamine biosynthesis and CsGOGAT1-catalyzed glutamate biosynthesis were more active, and CsGGT2-catalyzed theanine catabolism was weaker in new shoots of these albino/etiolated tea plant cultivars. Therefore, the high theanine accumulation in albino/etiolated shoots is probably contributed by the strong theanine biosynthesis and weak catabolism in new shoots. These findings provided more comprehensive insights into the high accumulation of theanine in new shoots of albino/etiolated tea cultivars, and the knowledge can be used in plant breeding for new cultivars with higher theanine accumulation. Citation: Zhu B, Qiao S, Li M, Cheng H, Ma Q, et al. 2023. Strong biosynthesis and weak catabolism of theanine in new shoots contribute to the high theanine accumulation in Albino/etiolated tea plant (Camellia sinensis). Beverage Plant Research 3:23 https://doi.
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Low mental energy can contribute to decreased productivity, altered life balance, decreased physical performance, and ultimately affect quality of life. As such, there is a great demand for food and beverage products that positively impact mental energy. Numerous products claim to alter mental energy making continued review of the scientific evidence critical. The objective of this study was to conduct a scoping review of randomized controlled trials to evaluate the effect of 18 dietary ingredients on mental energy outcomes in adults without severe disease. Methods: A literature search, completed using PubMed, resulted in the identification of 2261 articles, 190 of which met eligibility from initial abstract review. Full-text review was completed on the 190 studies which resulted in 101 articles that fully met eligibility for inclusion in this study. The search strategy for two ingredients did not yield any eligible studies, leaving studies for 16 ingredients that were extracted and summarized by reported significantly improved outcomes for cognition, mood and perceived feelings, and sleep assessments. The preliminary results for several dietary ingredients directionally suggested a mental energy benefit (≥20% of outcomes), including ashwagandha, chamomile, dark chocolate, ginseng, green tea, lavender, lion's mane mushroom, maca, tart cherries, turmeric, and valerian root. The results of this scoping review suggest that of the 16 dietary ingredients reviewed, 11 may be promising for further exploration on their potential benefits in supporting mental energy. Given consumer demand and market growth for food and beverage products that positively impact mental energy; continued efforts in assessment method alignment and additional evaluation in well-designed trials is warranted. KEY TEACHING POINTSOf the 16 dietary ingredients reviewed, 11 (ashwagandha, chamomile, dark chocolate, ginseng, green tea, lavender, lion's mane mushroom, maca, melatonin foods, turmeric, and valerian root) may be promising for further exploration on their potential mental energy benefits.Dark chocolate, ginseng, ashwagandha, and lion's mane mushroom were the most promising ingredients for further evaluation in the cognition domain of the ingredients evaluated.Turmeric, maca, lavendar, and ashwagandha were the most promising ingredients for further evaluation in the mood and perceived feelings domain of the ingredients evaluated.Ashwagandha, chamomile, green tea, melatonin foods, valerian root were the most promising ingredients for further evaluation in the sleep domain of the ingredients evaluated.Additional, well-designed, consistent, clinical trials and systematic reviews are warranted as the challenge of heterogeneity in mental energy study design remains.
Article
Background: L-theanine, 2-amino-4-(ethylcarbamoyl) butyric acid, an amino acid detected in green tea leaves, is used as a dietary supplement to attenuate stress and enhance mood and cognition. Furthermore, L-theanine induces anxiolytic effects in humans. Recently, L-theanine was reported to reduce morphine physical dependence in primates, suggesting the potential usefulness of L-theanine for drug dependence intervention. Objective: The aim of this study is to determine whether L-theanine attenuates nicotine-withdrawal (somatic and affective signs) and nicotine reward in mice. We also investigated the effects of L-theanine on nicotinic receptors binding and function. Methods: ICR male mice rendered dependent to nicotine through implanted subcutaneous osmotic minipumps for 14 days undertook precipitated nicotine withdrawal by mecamylamine on day 15. Anxiety-like behaviors using LDB, somatic signs observation and hot plate latency were assessed consecutively after treatment with L-theanine. Furthermore, we examined the effect of L-theanine on acute nicotine responses and nicotine conditioned reward in mice and on expressed nicotinic receptors in oocytes. Key findings: L-theanine reduced in a dose-dependent manner anxiety-like behavior, hyperalgesia and somatic signs during nicotine withdrawal. Also, L-theanine decreased the nicotine CPP, but it did not affect the acute responses of nicotine. Finally, L-theanine did not alter the binding or the function of expressed α4β2 and α7 nAChRs. Conclusion: Our results support the potential of L-theanine as a promising candidate for treating nicotine dependence.
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Position Statement: The International Society of Sports Nutrition (ISSN) bases the following position stand on a critical analysis of the literature regarding the effects of energy drink (ED) or energy shot (ES) consumption on acute exercise performance, metabolism, and cognition, along with synergistic exercise-related performance outcomes and training adaptations. The following 13 points constitute the consensus of the Society and have been approved by the Research Committee of the Society: Energy drinks (ED) commonly contain caffeine, taurine, ginseng, guarana, carnitine, choline, B vitamins (vitamins B1, B2, B3, B5, B6, B9, and B12), vitamin C, vitamin A (beta carotene), vitamin D, electrolytes (sodium, potassium, magnesium, and calcium), sugars (nutritive and non-nutritive sweeteners), tyrosine, and L-theanine, with prevalence for each ingredient ranging from 1.3 to 100%. Energy drinks can enhance acute aerobic exercise performance, largely influenced by the amount of caffeine (> 200 mg or >3 mg∙kg bodyweight [BW⁻¹]) in the beverage. Although ED and ES contain several nutrients that are purported to affect mental and/or physical performance, the primary ergogenic nutrients in most ED and ES based on scientific evidence appear to be caffeine and/or the carbohydrate provision. The ergogenic value of caffeine on mental and physical performance has been well-established, but the potential additive benefits of other nutrients contained in ED and ES remains to be determined. Consuming ED and ES 10-60 minutes before exercise can improve mental focus, alertness, anaerobic performance, and/or endurance performance with doses >3 mg∙kg BW⁻¹. Consuming ED and ES containing at least 3 mg∙kg BW⁻¹ caffeine is most likely to benefit maximal lower-body power production. Consuming ED and ES can improve endurance, repeat sprint performance, and sport-specific tasks in the context of team sports. Many ED and ES contain numerous ingredients that either have not been studied or evaluated in combination with other nutrients contained in the ED or ES. For this reason, these products need to be studied to demonstrate efficacy of single- and multi-nutrient formulations for physical and cognitive performance as well as for safety. Limited evidence is available to suggest that consumption of low-calorie ED and ES during training and/or weight loss trials may provide ergogenic benefit and/or promote additional weight control, potentially through enhanced training capacity. However, ingestion of higher calorie ED may promote weight gain if the energy intake from consumption of ED is not carefully considered as part of the total daily energy intake. Individuals should consider the impact of regular coingestion of high glycemic index carbohydrates from ED and ES on metabolic health, blood glucose, and insulin levels. Adolescents (aged 12 through 18) should exercise caution and seek parental guidance when considering the consumption of ED and ES, particularly in excessive amounts (e.g. > 400 mg), as limited evidence is available regarding the safety of these products among this population. Additionally, ED and ES are not recommended for children (aged 2-12), those who are pregnant, trying to become pregnant, or breastfeeding and those who are sensitive to caffeine. Diabetics and individuals with preexisting cardiovascular, metabolic, hepatorenal, and/or neurologic disease who are taking medications that may be affected by high glycemic load foods, caffeine, and/or other stimulants should exercise caution and consult with their physician prior to consuming ED. The decision to consume ED or ES should be based upon the beverage’s content of carbohydrate, caffeine, and other nutrients and a thorough understanding of the potential side effects. Indiscriminate use of ED or ES, especially if multiple servings per day are consumed or when consumed with other caffeinated beverages and/or foods, may lead to adverse effects. The purpose of this review is to provide an update to the position stand of the International Society of Sports Nutrition (ISSN) integrating current literature on ED and ES in exercise, sport, and medicine. The effects of consuming these beverages on acute exercise performance, metabolism, markers of clinical health, and cognition are addressed, as well as more chronic effects when evaluating ED/ES use with exercise-related training adaptions.
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Present study aimed compared pharmacokinetic profile of sustained-release CaffXtend® capsules (SR-Caffeine) with immediate-release caffeine capsules (IR-Caffeine), and the effect of SR-caffeine on memory, motivation, concentration, and attention. This open-label, randomized, single-dose, two-treatment, two-sequence, two-period, two-way crossover oral bioavailability study block randomized (1:1) healthy subjects (N = 15) to receive SR-Caffeine (200 mg) and IR-Caffeine (200 mg). Blood samples were collected at 0.25, 0.50, 0.75, 1, 1.5, 2, 3, 4, 5, 6, 8, 10, 12, 24, 36 and 48 h in each period. Primary study outcome included comparing relative bioavailability of SR-Caffeine 200 mg and IR-Caffeine 200 mg under fasting conditions, and changes in caffeine research visual analogue scale (Caff-VAS) scores (‘relaxed’, ‘alert’, ‘jittery’, ‘tired’, ‘tense’, ‘headache’, ‘overall mood’ and ‘mentally fatigued’) were also evaluated. Fifteen subjects completed the study. Mean tmax was 4.08 ± 2.13h for SR-Caffeine compared to 0.83 ± 0.39h for IR-Caffeine, (p < 0.0001). Similarly, mean t½ was 7.07 ± 3.48h for SR-Caffeine compared to 5.78 ± 2.11h for IR-Caffeine (p = 0.04189). However, total exposure was similar for SR-Caffeine and IR-Caffeine (90% CI: 89.89–120.50% to 94.49–123.82% for geometric least square mean of ln-transformed AUC0-t and AUC0-∞). In the Caff-VAS evaluation, the SR-Caffeine group showed significantly better scores for ‘jitteriness’, ‘tiredness’, ‘alertness’ and ‘overall mood’ for 8–12 h than the IR-Caffeine group. No adverse events were reported. Results demonstrated sustained release of caffeine over 24 h from SR-Caffeine as compared to IR-Caffeine, which showed significant improvements in the scores for ‘relaxed’, ‘alertness’ and ‘overall mood’ and significantly lower scores for the parameters-‘jittery’ and ‘tired’ for extended period. Clinical trial registration: CTRI/2021/06/034185
Chapter
Enzymes are ubiquitous biocatalysts, represent a consolidated strategy in various food industries for the transformation of one biological compound to another. In contrast to conventional synthesis, enzymatic synthesis is an important technological advancement as a consequence of sustainability, substrate selectivity, nontoxicity, and low energy input. Therefore, there has been a growing trend in the use of free and immobilized enzymes in various food industrial applications, including the manufacturing of several functional foods and ingredients. Functional foods with health benefits beyond nutrition have gained much attention due to some factors such as interest in health-consciousness and the growing market. A variety of functional foods can be considered to be those fortified, wholes, enriched, or enhanced foods that represent physiological health benefits beyond the essential nutrients provision (e.g., vitamins and minerals) when consumed in adequate amounts on a regular basis. The initial components in functional food supplements naturally consist of fruit, food, beverage, grains, and supplement sectors at a low level. Nutraceuticals or functional food could be produced from the enzymatic reaction utilizable in one of the several areas of food science and technology, that is experiencing fast growth in recent years. Functional food could be enzymatically derived from various reactions: l-asparaginase, an intercellular enzyme, is used in the baking industry which suppresses acrylamide production. Addition of asparaginase is a recommended strategy to decrease the formation of acrylamide, as it catalysis the hydrolysis of asparagine to aspartic acid an amino acid with high nutritive value. Carbohydrate active enzymes such as β-glucanase which is able to proceed on glucose polysaccharides and to further develop the production of β-glucans, the saccharide made up of multiple sugar molecules. β-Glucan may offer a number of health benefits, including lowering cholesterol, improving blood sugar management, and boosting the immune system which is produced by the enzymatic process of beta d-glucose polysaccharide naturally occurring in the cell wall of cereals like oat. Chlorophyllase (Chlase) is widely distributed in the chloroplast, thylakoid membrane, and etioplast of higher plants, such as ferns, mosses, brown and red algae, and diatoms. Chlase catalysis is the degradation of chlorophyll to chlorophyllide (also called Chlide), which is introduced as a food colorant. l-Glutaminase is a catalyst for the production of l-theanine, a free amino acid with many health benefits. l-Theanine synthesis occurs from l-glutamine and ethylamine substrates through the transpeptidation reaction of l-glutaminase, and a demand for this amino acid is expected to grow rapidly in the industry. Lipids such as CLA (conjugated linoleic acid) are in the group of functional food, a result of CLA production from natural oil in the presence of a lipase. CLA is a natural derivative of essential fatty acid, linoleic acid which shows many beneficial effects on the immune system, role in obesity control and anticarcinogenic behavior phytases may find application in food processing to produce functional foods and phytic acid degradation. Phytase is able to decrease the antinutritional effect of phytate (inorganic phosphate complex) adverse impact of inorganic P excretion to the environment while increasing the digestibility of phosphorous (P), calcium, amino acids, and energy. γ-Amino butyric acid (GABA) is an active protein, in rice germ using protease or additives: produced by the decarboxylation of glutamic acid, GABA is catalyzed by glutamate decarboxylase, GABA functions as the main inhibitory neurotransmitter in the central nervous system. Tannase is able to catalyze the production of tea beverages while maintaining the tea’s original deep flavor. Engineering of enzymes is a potential strategy in the design of food development according to the specificity and enzyme structural changes. The next future step toward the commercialization of the enzymatic approach in food processing is to enhance their efficiency and mitigate adverse effects on the sensory properties of food products. In this chapter, we mainly highlighted the importance of selected enzymes on food development.
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An experiment was carried out to examine the effects of 40 mg of caffeine given in different drinks (coffee, water, tea, cola) on mood and performance. One hundred and forty-four volunteers were randomly assigned to one of the groups formed by combining the caffeine/placebo and drinks conditions. Following a baseline session measuring mood and different aspects of performance, the volunteers were given their drink and then carried out another test session 1 h later. Administration of the caffeine/placebo was double-blind. The results showed that those given caffeine reported greater alertness and anxiety at the end of the test session, as well as improved performance on choice reaction time tasks involving focused attention and categoric search, a semantic memory task and a delayed recognition memory task. The effect of the caffeine was not modified by the nature of the drink in which it was given. Overall, these results show that a dose of caffeine typical of the level found in commercial products can improve alertness and performance efficiency. Copyright © 1999 John Wiley & Sons, Ltd.
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Two experiments examined the effect of breakfast (1.89 MJ) and caffeine (4 mg/kg) on cognitive performance, mood and cardiovascular functioning. In the first experiment, breakfast had no effect on performance of sustained attention tasks, but it increased pulse rate and influenced mood. The mood effects after breakfast differed between a cooked breakfast and a cereal/toast breakfast. In contrast to the effects of breakfast, this relatively high dose of caffeine improved performance of the sustained attention tasks, increased blood pressure and increased mental alertness. In the second experiment, effects of a breakfast and caffeine on mood and cardiovascular functions confirmed the results of the first study. The breakfast improved performance on free recall and recognition memory tasks, had no effect on a semantic memory task and impaired the accuracy of performing a logical reasoning task. In contrast to this, caffeine improved performance on the semantic memory, logical reasoning, free recall and recognition memory tasks. Overall, these results show that breakfast can improve performance in some but not all cognitive tasks and that these changes are very different from those observed after lunch, and those produced by caffeine.
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The literature suggests that the following effects on behavior of adult humans may occur when individuals consume moderate amounts of caffeine. (1) Caffeine increases alertness and reduces fatigue. This may be especially important in low arousal situations (e.g. working at night). (2) Caffeine improves performance on vigilance tasks and simple tasks that require sustained response. Again, these effects are often clearest when alertness is reduced, although there is evidence that benefits may still occur when the person is unimpaired. (3) Effects on more complex tasks are difficult to assess and probably involve interactions between the caffeine and other variables which increase alertness (e.g. personality and time of day). (4) In contrast to the effects of caffeine consumption, withdrawal of caffeine has few effects on performance. There is often an increase in negative mood following withdrawal of caffeine, but such effects may largely reflect the expectancies of the volunteers and the failure to conduct "blind" studies. (5) Regular caffeine usage appears to be beneficial, with higher users having better mental functioning. (6) Most people are very good at controlling their caffeine consumption to maximise the above positive effects. For example, the pattern of consumption over the day shows that caffeine is often consumed to increase alertness. Indeed, many people do not consume much caffeine later in the day since it is important not to be alert when one goes to sleep. In contrast to effects found from normal caffeine intake, there are reports that have demonstrated negative effects when very large amounts are given or sensitive groups (e.g. patients with anxiety disorders) were studied. In this context caffeine has been shown to increase anxiety and impair sleep. There is also some evidence that fine motor control may be impaired as a function of the increase in anxiety. Overall, the global picture that emerges depends on whether one focuses on effects that are likely to be present when caffeine is consumed in moderation by the majority of the population or on the effects found in extreme conditions. The evidence clearly shows that levels of caffeine consumed by most people have largely positive effects on behavior. Excessive consumption can lead to problems, especially in sensitive individuals.
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Melissa officinalis (Lemon balm) is a herbal medicine that has traditionally been attributed with memory-enhancing properties, but which is currently more widely used as a mild sedative and sleep aid. In a previous study it was demonstrated that a commercial Melissa extract led to dose-specific increases in calmness, and dose-dependent decrements in timed memory task performance. However, the extract utilized in that study did not exhibit in vitro cholinergic receptor-binding properties. The current study involved an initial screening of samples of M. officinalis for human acetylcholinesterase inhibition and cholinergic receptor-binding properties. The cognitive and mood effects of single doses of the most cholinergically active dried leaf were then assessed in a randomized, placebo-controlled, double-blind, balanced crossover study. Following the in vitro analysis, 20 healthy, young participants received single doses of 600, 1000, and 1600 mg of encapsulated dried leaf, or a matching placebo, at 7-day intervals. Cognitive performance and mood were assessed predose and at 1, 3, and 6 h postdose using the Cognitive Drug Research computerized assessment battery and Bond-Lader visual analog scales, respectively. In vitro analysis of the chosen extract established IC(50) concentrations of 0.18 and 3.47 mg ml(-1), respectively, for the displacement of [(3)H]-(N)-nicotine and [(3)H]-(N)-scopolamine from nicotinic and muscarinic receptors in the human cerebral cortex tissue. However, no cholinesterase inhibitory properties were detected. The most notable cognitive and mood effects were improved memory performance and increased 'calmness' at all postdose time points for the highest (1600 mg) dose. However, while the profile of results was overwhelmingly favorable for the highest dose, decrements in the speed of timed memory task performance and on a rapid visual information-processing task increased with decreasing dose. These results suggest that doses of Melissa officinalis at or above the maximum employed here can improve cognitive performance and mood and may therefore be a valuable adjunct in the treatment of Alzheimer's disease. The results also suggest that different preparations derived from the same plant species may exhibit different properties depending on the process used for the sample preparation.
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There have been numerous studies on the effects of caffeine on behaviour and cardiovascular function. It is now important to clarify the mechanisms that underlie such effects, and the main objective of the present study was to investigate whether changes in central noradrenaline underlie some of the behavioural and cardiovascular effects of caffeine. This was examined using a clonidine challenge paradigm. Twenty-four healthy volunteers were assigned to one of four conditions: (i) clonidine/caffeine; (ii) clonidine/placebo; (iii) placebo/caffeine: (iv) placebo/placebo. Baseline measurements of mood, cognitive performance, saccadic eye movements and cardiovascular function were recorded. Subsequently, volunteers were given either clonidine (200 microg) or placebo and consumed coffee containing caffeine (1.5 mg/kg) or placebo. The test battery was then repeated 30 min, 150 min and 270 min later. A second cup of coffee (with the same amount of caffeine as the first) was consumed 120 min after the first cup. The results showed that clonidine reduced alertness, impaired many aspects of performance and slowed saccadic eye movements; caffeine removed many of these impairments. Both clonidine and caffeine influenced blood pressure (clonidine reduced it, caffeine raised it) but the effects appeared to be independent, suggesting that separate mechanisms were involved. In addition, there were some behavioural effects of caffeine that were independent of the clonidine effect (e.g. effects on speed of encoding of new information) and these may reflect other neurotransmitter systems (e.g cholinergic effects). Overall, the results suggest that caffeine counteracts reductions in the turnover of central noradrenaline. This mechanism may underlie the beneficial effects of caffeine seen in low alertness states.
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L-Theanine (delta-glutamylethylamide) is one of the predominant amino acids ordinarily found in green tea, and historically has been used as a relaxing agent. The current study examined the acute effects of L-theanine in comparison with a standard benzodiazepine anxiolytic, alprazolam and placebo on behavioural measures of anxiety in healthy human subjects using the model of anticipatory anxiety (AA). Sixteen healthy volunteers received alprazolam (1 mg), L-theanine (200 mg) or placebo in a double-blind placebo-controlled repeated measures design. The acute effects of alprazolam and L-theanine were assessed under a relaxed and experimentally induced anxiety condition. Subjective self-reports of anxiety including BAI, VAMS, STAI state anxiety, were obtained during both task conditions at pre- and post-drug administrations. The results showed some evidence for relaxing effects of L-theanine during the baseline condition on the tranquil-troubled subscale of the VAMS. Alprazolam did not exert any anxiolytic effects in comparison with the placebo on any of the measures during the relaxed state. Neither L-theanine nor alprazalam had any significant anxiolytic effects during the experimentally induced anxiety state. The findings suggest that while L-theanine may have some relaxing effects under resting conditions, neither L-theanine not alprazolam demonstrate any acute anxiolytic effects under conditions of increased anxiety in the AA model.
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Both glucose and caffeine can improve aspects of cognitive performance and, in the case of caffeine, mood. There are few studies investigating the effects of the two substances in combination. We assessed the mood, cognitive and physiological effects of a soft drink containing caffeine and glucose as well as flavouring levels of herbal extracts. The effects of different drink fractions were also evaluated. Using a randomised, double-blind, balanced, five-way crossover design, 20 participants who were overnight fasted and caffeine-deprived received 250 ml drinks containing 37.5 g glucose; 75 mg caffeine; ginseng and ginkgo biloba at flavouring levels; a whole drink (containing all these substances) or a placebo (vehicle). Participants were assessed in each drink condition, separated by a 7-day wash-out period. Cognitive, psychomotor and mood assessment took place immediately prior to the drink then 30 min thereafter. The primary outcome measures included five aspects of cognitive performance from the Cognitive Drug Research assessment battery. Mood, heart rate and blood glucose levels were also monitored. Compared with placebo, the whole drink resulted in significantly improved performance on "secondary memory" and "speed of attention" factors. There were no other cognitive or mood effects. This pattern of results would not be predicted from the effects of glucose and caffeine in isolation, either as seen here or from the literature addressing the effects of the substances in isolation. These data suggest that there is some degree of synergy between the cognition-modulating effects of glucose and caffeine which merits further investigation.
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The cognitive and mood effects of caffeine are well documented. However, the majority of studies in this area involve caffeine-deprived, habitual caffeine users. It is therefore unclear whether any beneficial findings are due to the positive effects of caffeine or to the alleviation of caffeine withdrawal. The present placebo-controlled, double-blind, balanced crossover study investigated the acute cognitive and mood effects of caffeine in habitual users and habitual non-users of caffeine. Following overnight caffeine withdrawal, 24 habitual caffeine consumers (mean=217 mg/day) and 24 habitual non-consumers (20 mg/day) received a 150 ml drink containing either 75 or 150 mg of caffeine or a matching placebo, at intervals of > or =48 h. Cognitive and mood assessments were undertaken at baseline and 30 min post-drink. These included the Cognitive Drug Research computerised test battery, two serial subtraction tasks, a sentence verification task and subjective visual analogue mood scales. There were no baseline differences between the groups' mood or performance. Following caffeine, there were significant improvements in simple reaction time, digit vigilance reaction time, numeric working memory reaction time and sentence verification accuracy, irrespective of group. Self-rated mental fatigue was reduced and ratings of alertness were significantly improved by caffeine independent of group. There were also group effects for rapid visual information processing false alarms and spatial memory accuracy with habitual consumers outperforming non-consumers. There was a single significant interaction of group and treatment effects on jittery ratings. Separate analyses of each groups' responses to caffeine revealed overlapping but differential responses to caffeine. Caffeine tended to benefit consumers' mood more while improving performance more in the non-consumers. These results do not support a withdrawal alleviation model. Differences in the patterns of responses to caffeine by habitual consumers and habitual non-consumers may go some way to explaining why some individuals become caffeine consumers.
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The present study aimed to systematically assess acute, dose-related behavioural effects of an extract of guaraná plant for the first time in humans. This double-blind, counterbalanced, placebo-controlled study ( n = 26) assessed the acute mood and cognitive effects throughout the day of four different doses (37.5mg, 75mg, 150mg and 300mg) of a standardised guaraná extract (PC-102). Assessment included the Cognitive Drug Research computerized test battery and Bond-Lader mood scales. Guaraná improved secondary memory performance and increased alert and content mood ratings. The two lower doses produced more positive cognitive effects than the higher doses. This research supports previous findings of cognitive improvements following 75mg guaraná and provides the first exploration of different dose effects of guaraná in humans. The findings suggest that the effects cannot be attributed to caffeine alone.
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Tea has anecdotally been associated with stress relief, but this has seldom been tested scientifically. To investigate the effects of 6 weeks of black tea consumption, compared with matched placebo, on subjective, cardiovascular, cortisol and platelet responses to acute stress, in a parallel group double-blind randomised design. Seventy-five healthy nonsmoking men were withdrawn from tea, coffee and caffeinated beverages for a 4-week wash-out phase during which they drank four cups per day of a caffeinated placebo. A pretreatment laboratory test session was carried out, followed by either placebo (n = 38) or active tea treatment (n = 37) for 6 weeks, then, a final test session. Cardiovascular measures were obtained before, during and after two challenging behavioural tasks, while cortisol, platelet and subjective measures were assessed before and after tasks. The tasks induced substantial increases in blood pressure, heart rate and subjective stress ratings, but responses did not differ between tea and placebo treatments. Platelet activation (assessed using flow cytometry) was lower following tea than placebo treatment in both baseline and post-stress samples (P < 0.005). The active tea group also showed lower post-task cortisol levels compared with placebo (P = 0.032), and a relative increase in subjective relaxation during the post-task recovery period (P = 0.036). Compared with placebo, 6 weeks of tea consumption leads to lower post-stress cortisol and greater subjective relaxation, together with reduced platelet activation. Black tea may have health benefits in part by aiding stress recovery.
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: Ingestion of the nonproteinic amino acid theanine (5-N-ethylglutamine) has been shown to increase oscillatory brain activity in the so-called alpha band (8-14 Hz) during resting electroencephalographic recordings in humans. Independently, alpha band activity has been shown to be a key component in selective attentional processes. Here, we set out to assess whether theanine would cause modulation of anticipatory alpha activity during selective attentional deployments to stimuli in different sensory modalities, a paradigm in which robust alpha attention effects have previously been established. : Electrophysiological data from 168 scalp electrode channels were recorded while participants performed a standard intersensory attentional cuing task. : As in previous studies, significantly greater alpha band activity was measured over parieto-occipital scalp for attentional deployments to the auditory modality than to the visual modality. Theanine ingestion resulted in a substantial overall decrease in background alpha levels relative to placebo while subjects were actively performing this demanding attention task. Despite this decrease in background alpha activity, attention-related alpha effects were significantly greater for the theanine condition. : This increase of attention-related anticipatory alpha over the right parieto-occipital scalp suggests that theanine may have a specific effect on the brain's attention circuitry. We conclude that theanine has clear psychoactive properties, and that it represents a potentially interesting, naturally occurring compound for further study, as it relates to the brain's attentional system.
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This chapter provides details about the production, trade, and consumption of caffeine, which is probably the world's most widely used drug. The focus is on caffeine derived from coffee, which accounts for about 54% of all caffeine use, because other chapters in the volume give details of tea and cocoa consumption. Tea accounts for about 43% of all caffeine consumption. Total world caffeine consumption in 1981 was estimated to be approximately 120,000 tonnes, equivalent to 70 mg a day for each inhabitant. The per capita rate of caffeine use in Canada and the United States is approximately three times that for the world as a whole, but only half that of a heavy coffee-consuming country such as Sweden or a heavy tea-consuming country such as the United Kingdom.
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L-Theanine is an amino acid found in green tea leaf and in its infusion, and is known to control excitement caused by caffeine. It is also known that the oral administration of L-theanine to rats results in a decrease of serotonin and increase of catecholamines in their brain. L-Theanine has been confirmed to be safe in animal experiments. We found recently that oral intake of L-theanine caused a feeling of relaxation among the human volunteers examined. These observations led us to do experiments on the effects of administration of L-theanine on the brain electric waves. Eight female university students were selected as volunteers. Four of them were ranked to be Grade I (the highest anxiety) and the remaining four, Grade V (the lowest anxiety) in an investigation done by the manifest anxiety scale method. A dose of oral administration of 200mg of L-theanine dissolved in 100ml of water resulted in the generation of a-electric waves in the occipital and parietal regions of the brains of the subjects. The emission intensity of α-brain waves (integrated as a function of investigation times and area) was significantly greater in the group of Grade I than that of Grade V. These results indicate the possibility for L-theanine to be applied to foods and beverages as a new type of functional food ingredient for its relaxation effect.
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It has previously been assumed that levels of caffeine typically found in decaffeinated beverages have no behavioural effects. However, recent findings from our laboratory indicate that caffeine doses as low as 9 mg have psychoactive properties which can endure for several hours. The current study aimed to establish the lowest active dose of caffeine and to ascertain the duration of any effects. Twenty participants took part in this randomised, placebo-controlled, double-blind, balanced-crossover study assessing the effects of three different doses of caffeine (2.5, 5, and 10 mg) administered in fruit juice. Cognitive performance, mood, autonomic activity and salivary caffeine were assessed pre-dose and at 1, 3, 6 and 9 h post-dose. Compared with placebo, performance was impaired by 2.5 mg, whilst 5 mg had negative effects on mood and mixed effects on performance and 10 mg improved performance. A number of these effects were apparent at 9 h post-treatment. Given that the average cup of decaffeinated coffee contains 3–5 mg caffeine, these results demonstrate that decaffeinated coffee is not inert as previously believed and this has implications for research which utilises decaffeinated coffee as placebo. Effects of caffeine are also longer-lasting than previously thought with effects apparent 9 h post-dose. This finding may offer an alternative explanation to withdrawal models for differing results in the literature pertaining to baseline performance in consumers and non-consumers of caffeine.
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Administered 16 visual analog scales to 8 normal Ss to test the validity of the scales in measuring drug effects; Ss received 150 mg of butobarbitone sodium, 15 and 30 mg of flurazepam, and a placebo. Results indicate that (a) there were no significant effects on Factor 1 (Alertness), but there was a tendency for Ss to rate themselves as more alert after placebo; (b) there was a significant Drug * Times interaction effect on Factor 2 (Contentedness); and (c) Factor 3 (Calmness) also showed a significant Drug * Times interaction effect which was caused by the anti-anxiety effect of flurazepam. (15 ref) (PsycINFO Database Record (c) 2004 APA, all rights reserved)
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Caffeine is thought to have stimulant-like behavioral effects on mood and performance. However few behavioral studies have examined this substance's acute effects when administered in a range of doses that include the low doses typically found in foods and over-the-counter drugs. We therefore gave single doses of caffeine (32, 64, 128 and 256 mg) to 20 healthy male subjects and assessed various aspects of performance and self-reported mood states, as well as plasma caffeine concentration. As little as 32 mg (which elevated plasma caffeine concentration to less than 1 microgram/ml), typical of the dose found in a single serving of a cola beverage, and less than that found in a single cup of coffee or a single dose of over-the-counter drugs, significantly improved auditory vigilance and visual reaction time. All other caffeine doses administered also significantly improved performance on these tests. No adverse behavioral effects, such as increased anxiety or impaired motor performance, were noted even at the highest dose administered.
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Theanine (N-ethylglutamine), a flavourous constituent of tea leaves, was studied in respect of the influence on the central nervous system in mice.Theanine was shown to inhibit the convulsive action of caffeine, but was ineffective against pentetrazole, picrotoxin, strychnine, pipradrol and bemegride as well as L-glutamine. Neither theanine nor L-glutamine effected on the prolongation of the sleeping time after the injection of hexobarbital sodium in mice. Using 14C-labeled theanine, it was found that the intraperitoneally administered theanine was taken up by brain tissue with out undergoing the metabolic changes in a 30minutes. The intracerebral level of γaminobutyric acid was shown to increase significantly at 30minutes following the intraperitoneal administration of theanine in mice.
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The objective of this study was to evaluate the effects of low doses (75 mg and 150 mg) of caffeine on mood and cognition in healthy people, with minimal abstinence of 1 h from caffeine. Improvements were obtained in cognition for attention, problem solving and delayed recall, but not immediate recall or working memory, but performance in the placebo condition was close to the maximum, giving little margin for improvement. For mood, there were statistically significant increase in clearheadedness, happiness and calmness and decreases in tenseness. These mood and performance-enhancing effects of caffeine cannot be seen as representing an alleviation of deficits induced by caffeine abstinence, because there was only minimal deprivation from caffeine.
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The mood and performance effects of caffeine deprivation (either 90 min, overnight, or at least 7 days) and ingestion (70 and 250 mg) were compared in young adults who were normally either moderate consumers (n = 49) or nonconsumers of caffeine (n = 18). Overnight caffeine deprivation produced dysphoric symptoms characteristic of caffeine withdrawal that were reduced, but still present, after longer-term abstinence. Acute caffeine intake affected the withdrawn consumers, nonwithdrawn consumers, and nonconsumers similarly. It increased jitteriness and decrease tiredness and headache. Furthermore, hand steadiness decreased as caffeine dose increased, whereas 70 mg, but not 250 mg, of caffeine was found to enhance performance on a simple reaction time task. These findings support the view that the negative effects experienced after overnight and longer-term caffeine deprivation play a significant role in influencing consumption of caffeine-containing drinks. Therefore, it would appear that to avoid the dysphoric symptoms resulting from both under- and overconsumption, regular caffeine consumers would have to regulate their caffeine intake fairly precisely.
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Scientific literature cites a wide range of values for caffeine content in food products. The authors suggest the following standard values for the United States: coffee (5 oz) 85 mg for ground roasted coffee, 60 mg for instant and 3 mg for decaffeinated; tea (5 oz): 30 mg for leaf/bag and 20 mg for instant; colas: 18 mg/6 oz serving; cocoa/hot chocolate: 4 mg/5 oz; chocolate milk: 4 mg/6 oz; chocolate candy: 1.5-6.0 mg/oz. Some products from the United Kingdom and Denmark have higher caffeine content. Caffeine consumption survey data are limited. Based on product usage and available consumption data, the authors suggest a mean daily caffeine intake for US consumers of 4 mg/kg. Among children younger than 18 years of age who are consumers of caffeine-containing foods, the mean daily caffeine intake is about 1 mg/kg. Both adults and children in Denmark and UK have higher levels of caffeine intake.
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Psychopharmacological studies using caffeinated beverages or caffeine have rarely considered temporal effects on psychological and physiological function or the specific contribution of caffeine, hot water, or beverage type to the observed effects. The effect of 400 ml hot tea, coffee, and water consumption on systolic and diastolic blood pressure (SBP and DBP), heart rate, skin conductance (a measure of sympathetic nervous system activation), skin temperature, salivary cortisol, and mood were monitored in 16 healthy caffeine-withdrawn (14 h) subjects in a complete crossover design. Beverages were ingested with/without 100 mg caffeine and milk (tea/coffee only). Hot beverage ingestion rapidly increased skin conductance and temperature (+1.7 degrees C) with peak effects observed only 10-30 min post-consumption. Caffeine in the beverage rapidly augmented skin conductance responses but, in contrast to the effect of hot water, reduced the skin temperature response and increased SBP (+2.8 mmHg) and DBP (+2.1 mmHg) 30-60 min post-consumption. Both caffeine and milk addition to beverages independently improved mood and reduced anxiety 30 and 60 min post-consumption. Milk addition had no other effects apart from attenuating the transient increase in physiological responses associated with the drinking phase. There were no effects of beverage consumption on salivary cortisol or of beverage vehicle on salivary caffeine levels, the latter indicating that caffeine pharmacokinetics was similar in both tea and coffee, and not different from caffeinated water. In keeping with this, the responses to tea and coffee ingestion were similar and largely accounted for by the effects of hot water and caffeine. However, tea potentiated the increase in skin temperature compared to coffee and water indicative of a greater vasodilatory response plausibly related to the presence of flavonoids in tea. We conclude that ingestion of hot caffeinated beverages stimulates physiological processes faster than hitherto described, primarily via the effects of hot water and caffeine, but with beverage type and milk playing important modulatory roles.
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Although caffeine is the most widely used behaviorally active drug in the world, caffeine physical dependence has been only moderately well characterized in humans. Four double-blind experiments were conducted in independent groups of healthy participants to assess the conditions under which withdrawal symptoms occur upon cessation of low to moderate doses of caffeine. In experiment 1, there was no evidence that the range or magnitude of caffeine withdrawal symptoms differed when 300 mg of caffeine was consumed as a single dose in the morning versus 100 mg at three time points across the day. In experiment 2, both the range and severity of withdrawal increased as a function of caffeine maintenance dose (100, 300, and 600 mg/day), with even the lowest dose (100 mg) producing significant caffeine withdrawal. Experiment 3 showed that when individuals were maintained on 300 mg caffeine/day and tested with a range of lower doses (200, 100, 50, 25, and 0 mg/day), a substantial reduction in caffeine consumption (</=100 mg/day) was necessary for the manifestation of caffeine withdrawal. Experiment 4 manipulated duration of exposure to caffeine (1, 3, 7, or 14 days of 300 mg/day) and showed that caffeine withdrawal occurred after as little as 3 days of caffeine exposure, with a somewhat increased severity of withdrawal observed after 7 or 14 days of exposure. As a whole, this set of experiments provides the most complete parametric characterization of caffeine withdrawal to date and suggests that caffeine physical dependence can occur under more modest conditions (i.e., fewer doses per day, lower daily dose, shorter duration of exposure) than previously recognized.
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It was recently established that supplemental oxygen administration significantly enhances memory formation in healthy young adults. In the present study, a double-blind, placebo-controled design was employed to assess the cognitive and physiological effects of subjects' inspiration of oxygen or air (control) prior to undergoing simple memory and reaction-time tasks. Arterial blood oxygen saturation and heart rate were monitored during each of six phases of the experiment, corresponding to baseline, gas inhalation, word presentation, reaction time, distractor and word recall, respectively. The results confirm that oxygen administration significantly enhances cognitive performance above that seen in the air inhalation condition. Subjects who received oxygen recalled more words and had faster reaction times. Moreover, compared to participants who inhaled air, they exhibited significant hyperoxia during gas administration, word presentation, and the reaction-time task, but not at other phases of the experiment. Compared to baseline, heart rate was significantly elevated during the word presentation, reaction-time, and distractor tasks in both the air and oxygen groups. In the oxygen group, significant correlations were found between changes in oxygen saturation and cognitive performance. In the air group, greater changes in heart rate were associated with more improved cognitive performance. These results are discussed in the context of cognitive demand and metabolic supply. It is suggested that under periods of cognitive demand a number of physiological responses are brought into play that serve to increase the delivery of metabolic substrates to active neural tissue. These mechanisms can be supplemented by increased availability of circulating blood oxygen, resulting in an augmentation of cognitive performance. Heart rate reactivity and the capacity for increased blood oxygen appear to be important physiological individual differences mediating these phenomena.
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In this study, the inhibiting action of theanine on the excitation by caffeine at the concentration regularly associated with drinking tea was investigated using electroencephalography (EEG) in rats. First, the stimulatory action by caffeine i.v. administration at a level higher than 5 micromol/kg (0.970 mg/kg) b.w. was shown by means of brain wave analysis, and this level was suggested as the minimum dose of caffeine as a stimulant. Next, the stimulatory effects of caffeine were inhibited by an i.v. administration of theanine at a level higher than 5 micromol/kg (0.781 mg/kg) b.w., and the results suggested that theanine has an antagonistic effect on caffeine's stimulatory action at an almost equivalent molar concentration. On the other hand, the excitatory effects were shown in the rat i.v. administered 1 and 2 micromol/kg (0.174 and 0.348 mg/kg) b.w. of theanine alone. These results suggested two effects of theanine, depending on its concentration.
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Rationale: The effects of caffeine, especially caffeinated coffee, on human performance have been extensively studied. However, few studies have been naturalistic representations of how tea/coffee is normally consumed in terms of dose and time of consumption. Objectives: This study investigated the effects of day-long consumption of tea, coffee and water on cognitive and psychomotor performance, and sleep quality at night. Methods: Thirty healthy volunteers received equal volume drinks equivalent to either 1 or 2 cups of tea (containing 37.5 mg or 75 mg caffeine), or coffee (75 mg or 150 mg caffeine), or water, in a randomised five-way crossover design. Drinks were administered on four occasions during the day (0900, 1300, 1700 and 2300 hours). A psychometric battery consisting of critical flicker fusion (CFF), choice reaction time (CRT) and subjective sedation (LARS) tests, was administered pre-dose and at frequent time points post-dose. The Leeds Sleep Evaluation Questionnaire (LSEQ) was completed each morning and a wrist actigraph was worn for the duration of the study. Results: Caffeinated beverages maintained CFF threshold over the whole day (P<0.05), independent of caffeine dose or beverage type. During the acute phase of beverage ingestion, caffeine significantly sustained performance compared to water after the first beverage for CFF and subjective sedation (P<0.05), and after the second beverage for the Recognition component of the CRT task (P<0.05). Additionally, there were significant differences between tea and coffee at 75 mg caffeine after the first drink. Compared to coffee, tea produced a significant increase in CFF threshold between 30 and 90 min post-consumption (P<0.01). However, following the second beverage caffeinated coffee at 75 mg significantly improved reaction time (P<0.05), compared to tea at the same dose, for the Recognition component of the CRT task. Caffeinated beverages had a dose dependent negative effect on sleep onset (P<0.001), sleep time (P<0.001) and sleep quality (P<0.001). Conclusions: These results indicate that ingestion of caffeinated beverages may maintain aspects of cognitive and psychomotor performance throughout the day and evening when caffeinated beverages are administered repeatedly. This study also demonstrates that day-long tea consumption produces similar alerting effects to coffee, despite lower caffeine levels, but is less likely to disrupt sleep. Other differences between tea and coffee were more subtle, and require further investigation.
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It has previously been demonstrated in separate studies that single doses of Ginkgo biloba, Panax ginseng, and a combination of the two extracts can improve different aspects of cognitive performance in healthy young volunteers. The present study directly compared the effects of single doses of G. biloba, ginseng, and a product combining the two on aspects of mood and cognitive performance in the same cohort of healthy, young adult volunteers. The study followed a randomised placebo-controlled, double-blind, balanced, cross-over design. Twenty participants received 360 mg of ginkgo, 400 mg of ginseng, 960 mg of a product combining the two extracts, and a matching placebo. Treatment order was dictated by random allocation to a Latin square, with a 7-day wash-out period between treatments. Cognitive testing comprised completion of the Cognitive Drug Research (CDR) computerised assessment battery and two serial subtraction mental arithmetic tasks. Mood was assessed with Bond-Lader visual analogue scales. Following a baseline cognitive assessment, further test sessions took place 1, 2.5, 4, and 6 h after the day's treatment was taken. The results largely supported previous findings. All three treatments were associated with improved secondary memory performance on the CDR battery, with the ginseng condition evincing some improvement in the speed of performing memory tasks and in the accuracy of attentional tasks. Following ginkgo and the ginkgo/ginseng combination performance of both the Serial Threes and Serial Sevens, subtraction tasks was also improved at the later testing sessions. No modulation of the speed of performing attention tasks was evident. Improvements in self-rated mood was also found following ginkgo and to a lesser extent the combination product.
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Unlike other CNS depressants, alcohol intoxication can be associated with increased error rates, coupled with unaffected (or speeded) response rates during psychomotor and cognitive processing. The present study examined whether concurrent consumption of caffeine may differentially affect these aspects of alcohol and performance. A randomised, double‐blind, placebo‐controlled design was utilised in which 64 healthy young volunteers received either 0.66 g/kg alcohol, caffeine (110–120 mg), both or neither. Performance was assessed using a four choice reaction time task (FCRT) with elements of repetitive (predictable) and random stimuli sequences and the digit symbol substitution task (DSST). Individuals on alcohol made significantly more errors during both fixed and random FCRT sequences, and there was evidence of weak antagonism of these effects by caffeine on the latter measure. On the DSST test of psychomotor speed, alcohol was associated with a significant slowing, the caffeine group were significantly faster and there was clear antagonism of the effects of alcohol by caffeine. These findings confirm that alcohol consumption is associated a greater number of errors and provide some evidence for task‐specific antagonism of alcohol's cognitive effects by caffeine. Copyright © 2002 John Wiley & Sons, Ltd.
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Several studies have reported that administration of a low dose of alcohol is capable of retrograde enhancement of memory. It has been postulated that the neurobiological mechanisms underlying this effect may involve the liberation of glucose and/or activation of reward centers. Here the effects of a low dose of alcohol were compared to those of glucose on kinesthetic memory. Mood and blood glucose levels were also measured. Compared with a placebo, both glucose and alcohol significantly enhanced kinesthetic memory performance. Only glucose ingestion resulted in significantly elevated blood glucose levels. The three groups' mood scores were statistically indistinguishable. Low-dose alcohol consumption does not result in the release of glucose nor does it affect any aspect of mood, at least as measured here. These results confirm that kinesthetic memory can be improved by administration of alcohol and extend the range of tasks which are sensitive to enhancement by glucose.
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The extent to which the measured (and felt) psychostimulant effects of caffeine represent a real benefit of caffeine consumption or merely withdrawal reversal is unclear. Results showing positive psychostimulant effects of acute caffeine administration in habitual non-consumers of caffeine would provide evidence for a net benefit of caffeine unconfounded by withdrawal. To compare the mood, alerting, psychomotor and reinforcing effects of caffeine in caffeine non-consumers and acutely (overnight) withdrawn caffeine consumers. In experiment 1, these participants consumed two differently flavoured drinks, one containing 100 mg caffeine and the other containing no caffeine. Each drink was consumed on 4 separate days in semi-random order, and self-ratings of mood and alertness were completed before and after drink consumption. On day 9, both drinks contained 50 mg caffeine and drink preference (choice) and intake were assessed. In experiment 2, mood, alertness and performance on a long-duration simple reaction time task were assessed before and after administration of 100 mg or placebo in a single test session. Prior to receiving caffeine, the (overnight withdrawn) caffeine consumers were less alert and more tense than the non-consumers. Caffeine only had significant reinforcing, mood and psychomotor performance effects in the caffeine consumers. The reinforcing effect of caffeine was evident from an effect on drink intake, but drink choice was unaffected. Caffeine increased self-rated alertness of both caffeine consumers and non-consumers; however, for some of the non-consumers this was associated with a worsening of performance. These results support the hypothesis that the psychostimulant and related effects of caffeine are due largely to withdrawal reversal.
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The primary target of licensed drugs for the treatment of Alzheimer's disease is the inhibition of the enzyme acetylcholinesterase, although preventing beta-amyloidosis is a prime target for drugs in development. The in vitro dual anti-cholinesterase and beta-secretase activities of Camellia sinensis L. extract (tea) is reported. Green and black tea inhibited human acetylcholinesterase (AChE) with IC(50) values of 0.03 mg/mL and 0.06 mg/mL respectively, and human butyrylcholinesterase (BuChE) with IC(50) values 0.05 mg/mL. Green tea at a final assay concentration of 0.03 mg/mL inhibited beta-secretase by 38%. These novel findings suggest that tea infusions contain biologically active principles, perhaps acting synergistically, that may be used to retard the progression of the disease assuming that these principles, yet to be identified, reach the brain.
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Caffeine elevates cortisol secretion, and caffeine is often consumed in conjunction with exercise or mental stress. The interactions of caffeine and stress on cortisol secretion have not been explored adequately in women. We measured cortisol levels at eight times on days when healthy men and women consumed caffeine (250 mg x 3) and underwent either mental stress or dynamic exercise protocols, followed by a midday meal, in a double blind, placebo-controlled, crossover design. Men and women had similar cortisol levels at the predrug baselines, but they responded differently to mental stress and exercise. The cortisol response to mental stress was smaller in women than in men (p=.003). Caffeine acted in concert with mental stress to further increase cortisol levels (p=.011), the effect was similar in men and women. Exercise alone did not increase cortisol, but caffeine taken before exercise elevated cortisol in both men and women (ps<.05). After a postexercise meal, the women had a larger cortisol response than the men, and this effect was greater after caffeine (p<.01). Cortisol release in response to stress and caffeine therefore appears to be a function of the type of stressor and the sex of the subject. However, repeated caffeine doses increased cortisol levels across the test day without regard to the sex of the subject or type of stressor employed (p<.00001). Caffeine may elevate cortisol by stimulating the central nervous system in men but may interact with peripheral metabolic mechanisms in women.