Article

Effects of L-theanine on attention and reaction time response

Authors:
  • Taiyo Kagaku Co.Ltd. Yokkaichi, Mie, Japan
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Abstract

Previous human studies revealed that l-theanine influences brain function. The current study was designed to evaluate the affect of l-theanine (Suntheanine®) on attention and reaction time response in 18 normal healthy University student volunteers. In accordance with preliminary analysis of the manifest anxiety scale (MAS), the subjects were divided into two groups referred to as high anxiety propensity group and the minimal anxiety propensity group. Both groups received l-theanine (200mg/100ml water) and placebo (100ml water) in a double blind repeated measurement design protocol. Assessments were performed for 15–60min after consumption under a relaxed condition upon exerting an experimentally induced visual attentional task as well as audio response tests. Self-reports of anxiety as State-Trait Anxiety Inventory (STAI) was characterized at post experiments. Alpha bands electroencephalographic activity and heart rate were recorded throughout the trial. The results demonstrate the significant enhanced activity of alpha bands, descending heart rate, elevated visual attentional performance, and improved reaction time response among high anxiety propensity subjects compared to a placebo. However, no significant differences were noticed among subjects with a minimal anxiety propensity. Results evidently demonstrated that l-theanine clearly has a pronounced effect on attention performance and reaction time response in normal healthy subjects prone to have high anxiety.

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... A list of all studies and outcome measures included in the review is displayed in Table 1. 10,14,[21][22][23][24][25][26][27][28][29] Outcome measures of mood ...
... Data for STAI-S were available from four studies. 10,22,28,29 SMDs are presented in Table 3 according to each treatment and time point. For the study by Lu et al., 10 SDs for the change from baseline (baseline to postdose) data were not available. ...
... Three studies were included in the meta-analysis. 22,28,29 Using a randomeffects model (k = 3, Q(2) = 1.20, P > 0.05, I 2 = 0%), the average SMD was estimated to be −0.04 (SE = 0.17), which was nonsignificant. ...
Article
A systematic review and meta-analysis was conducted on 11 randomized placebo-controlled human studies of acute effects of tea constituents L-theanine and epigallocatechin gallate, administered alone or in combination with caffeine, on cognitive function and mood. The outcome measures of mood were alertness, calmness, and contentedness, derived from the Bond-Lader scales, and state anxiety, from the State-Trait Anxiety Inventory. Cognitive measures assessed were attentional switch, intersensory attention, and rapid visual information processing. Standardized mean differences between placebo and treatment groups are presented for each study and outcome measure. Meta-analysis using a random-effects model was conducted when data were available for three or more studies. Evidence of moderate effect sizes in favor of combined caffeine and L-theanine in the first 2 hours postdose were found for outcome measures Bond-Lader alertness, attentional switching accuracy, and, to a lesser extent, some unisensory and multisensory attentional outcomes. Moderator analysis of caffeine and L-theanine doses revealed trends toward greater change in effect size for caffeine dose than for L-theanine dose, particularly during the first hour postdose.
... L-theanine is often advertised with claims of enhancing alertness and attention [16,20,21]. Several single-dose, placebo-controlled trials have investigated the acute attentional effects of L-theanine on healthy human volunteers using behavioral, neurophysiological and functional neuroimaging indices of selective attention [23][24][25][26][27][28][29][30]. These studies have produced mixed results in behavioral outcome measures, but those that examined neurophysiological measures of selective attention have produced more consistent results. ...
... Effect of high-doses of L-theanine on reaction time varies widely in the reported literature. Auditory attention tasks show 200 mg of L-theanine to cause either delay [25] or no change [24] in reaction time in healthy young volunteers. We have consistently observed a 200-mg dose to improve color discrimination reaction time [28,29], yet others have observed no significant change in visual simple reaction time or choice reaction time [42,43], or reaction time in a visuospatial attention task [26]. ...
... As for the complexity, it is possible that these selective attention tasks were not demanding enough, thus leading to a possible ceiling effect at the behavioral level (as shown by high accuracy rates) among healthy young participants of those studies. The complexity the tasks were particularly constrained by the abstract nature of the stimuli such as tones [24], colored flashes [28][29][30], directional arrows [26,27,43,44] that required lower order attentional processing than in real-life scenarios. Therefore, we believe further exploration of behavioral effects of L-theanine in the future could employ more demanding and ecologically valid stimuli and task paradigms. ...
Article
Objective: L-theanine, a non-proteinic amino acid found in tea, is known to enhance attention particularly in high doses, with no reported adverse effects. We aimed to determine whether oral administration of L-theanine acutely enhances neurophysiological measures of selective attention in a dose-dependent manner. Methods: In a double-blind, placebo-controlled, counterbalanced, 4-way crossover study in a group of 27 healthy young adults, we compared the effects of 3 doses of L-theanine (100, 200 and 400 mg) with a placebo (distilled water) on latencies of amplitudes of attentive and pre-attentive cognitive event-related potentials (ERPs) recorded in an auditory stimulus discrimination task, before and 50 min after dosing. Results: Compared to the placebo, 400 mg of theanine showed a significant reduction in the latency of the parietal P3b ERP component (p < 0.05), whereas no significant changes were observed with lower doses. A subsequent exploratory regression showed that each 100-mg increase in dose reduces the P3b latency by 4 ms (p < 0.05). No dose–response effect was observed in P3b amplitude, pre-attentive ERP components or reaction time. Discussion: The findings indicate L-theanine can increase attentional processing of auditory information in a dose-dependent manner. The linear dose–response attentional effects we observed warrant further studies with higher doses of L-theanine.
... However, compared to caffeine or theanine-caffeine combination only few studies have examined neurocognitive effects of theanine alone on humans. 8,[19][20][21][22][23] Limited evidence suggest moderate doses theanine (100 mg), unlike caffeine (50 mg), does not to elicit significant positive attentional effects. 19,22 Although proved to be safe in animal experiments in high doses, 24,25 evidence on attentional effects of high-dose theanine is scarce and inconsistent, perhaps owing to differences in the subject groups, time of testing, and outcome variables. ...
... 19,22 Although proved to be safe in animal experiments in high doses, 24,25 evidence on attentional effects of high-dose theanine is scarce and inconsistent, perhaps owing to differences in the subject groups, time of testing, and outcome variables. 8,20,21 Higashiyama et al. 21 found that 200 mg of theanine to shorten reaction time in individuals with high propensity for anxiety within the first hour post-dose, but Haskell et al. 8 did not find any significant effects of 250 mg of theanine on reaction time at 30 minutes or 90 minutes post-dose and Gomez-Ramirez et al. 20 found delayed reaction times however do not specify the time of testing. ...
... 19,22 Although proved to be safe in animal experiments in high doses, 24,25 evidence on attentional effects of high-dose theanine is scarce and inconsistent, perhaps owing to differences in the subject groups, time of testing, and outcome variables. 8,20,21 Higashiyama et al. 21 found that 200 mg of theanine to shorten reaction time in individuals with high propensity for anxiety within the first hour post-dose, but Haskell et al. 8 did not find any significant effects of 250 mg of theanine on reaction time at 30 minutes or 90 minutes post-dose and Gomez-Ramirez et al. 20 found delayed reaction times however do not specify the time of testing. ...
Article
Objective: l-theanine is a constituent of tea which is claimed to enhance cognitive functions. We aimed to determine whether theanine and theanine-caffeine combination have acute positive effects on cognitive and neurophysiological measures of attention, compared to caffeine (a positive control) and a placebo in healthy individuals. Design: In a placebo-controlled, five-way crossover trial in 20 healthy male volunteers, we compared the effects of l-theanine (200 mg), caffeine (160 mg), their combination, black tea (one cup) and a placebo (distilled water) on cognitive (simple [SVRT] and recognition visual reaction time [RVRT]) and neurophysiological (event-related potentials [ERPs]) measures of attention. We also recorded visual (VEPs) and motor evoked potentials (MEPs) to examine any effects of treatments on peripheral visual and motor conduction, respectively. Results: Mean RVRT was significantly improved by theanine (P = 0.019), caffeine (P = 0.043), and theanine-caffeine combination (P = 0.001), but not by tea (P = 0.429) or placebo (P = 0.822). VEP or MEP latencies or SVRT did not show significant inter-treatment differences. Theanine (P = 0.001) and caffeine (P = 0.001) elicited significantly larger mean peak-to-peak N2-P300 ERP amplitudes than the placebo, whereas theanine-caffeine combination elicited a significantly larger mean N2-P300 amplitude than placebo (P < 0.001), theanine (P = 0.029) or caffeine (P = 0.005). No significant theanine × caffeine interaction was observed for RVRT or N2-P300 amplitude. Discussion: A dose of theanine equivalent of eight cups of back tea improves cognitive and neurophysiological measures of selective attention, to a degree that is comparable with that of caffeine. Theanine and caffeine seem to have additive effects on attention in high doses.
... Following removal of duplicates (n = 40), reviews, letters to the editor and articles not written in English (n = 177), the number of articles was reduced to 44. Nine articles [38,44,[46][47][48][49][50][51][52] met the inclusion criteria ( Fig. 1). Seven studies recruited participants with no known preexisting mental health issues, while two studies used participants with an existing mental health condition [44,49]. ...
... The total number of participants for all included studies was 270 with 134 males and 88 females ( Table 1). Two studies were conducted in males only [46,47], and one study did not provide the genders of its 48 participants [38]. ...
... The other three studies were designed to test for chronic effects and involved interventions over periods between seventeen days [50] to eight weeks [44,49]. In the acute single day intervention trials, participants consumed 200 mg/day [46][47][48]52], while in the chronic trials, Primary database search: n=261 ...
Article
Full-text available
The green tea amino acid, L-theanine (L-THE) is associated with several health benefits, including improvements in mood, cognition and a reduction of stress and anxiety-like symptoms. This systematic review evaluated the effect of pure L-THE intake, in the form of orally administered nutritional supplements, on stress responses and anxiety levels in human randomised controlled trials. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, 9 peer-reviewed journal articles were identified where L-THE as a supplement was compared to a control. Our findings suggest that supplementation of 200-400 mg/day of L-THE may assist in the reduction of stress and anxiety in people exposed to stressful conditions. Despite this finding, longer-term and larger cohort clinical studies, including those where L-THE is incorporated into the diet regularly, are needed to clinically justify the use of L-THE as a therapeutic agent to reduce stress and anxiety in people exposed to stressful conditions.
... Another study, which measured the effect of 200 mg L-theanine by means of EEG recordings found L-theanine to change the electrical activity in the brain indicated by increased alpha electric band [174]. Comparing the outcome of the six studies using EEG measures [116-119, 172, 174], it can be said that the findings are very diverse. ...
... Comparing the outcome of the six studies using EEG measures [116-119, 172, 174], it can be said that the findings are very diverse. In contrast to the studies from Gomez-Ramirez et al. [116,119,172,174]. Possible explanation for varying results could be low statistical powers, differences in caffeine abstinence, and treatment absorption periods. ...
... The acute administration of L-theanine has been repeatedly observed to induce relaxing or calming effects during relaxed or resting experimental state, which is attributed to the increase in alpha band electrocortical activity [173]. Only four studies investigated the effect of L-theanine on anxiety and other psychological stress types by means of subjective ratings [119,121,173,174]. According to Kimura et al. (2007), 200 mg L-theanine reduced subjective psychological stress during the performance of a stressful arithmetic task. ...
Article
Background: Green tea is traditionally known to induce mental clarity, cognitive function, physical activation and relaxation. Recently, a special green tea, matcha tea, is rapidly gaining popularity throughout the world and is frequently referred to as a mood- and brain food. Matcha tea consumption leads to much higher intake of green tea phytochemicals compared to regular green tea. Previous research on tea constituents caffeine, L-theanine, and epigallocatechin gallate (EGCG) repeatedly demonstrated benefits on mood and cognitive performance. These effects were observed when these phytochemicals were consumed separately and in combination. Methods: A review was conducted on 49 human intervention studies to summarize the research on acute psychoactive effects of caffeine, L-theanine, and EGCG on different dimensions of mood and cognitive performance. Conclusions: Caffeine was found to mainly improve performance on demanding long-duration cognitive tasks and self-reported alertness, arousal, and vigor. Significant effects already occurred at low doses of 40 mg. L-theanine alone improved self-reported relaxation, tension, and calmness starting at 200 mg. L-theanine and caffeine combined were found to particularly improve performance in attention-switching tasks and alertness, but to a lesser extent than caffeine alone. No conclusive evidence relating to effects induced by EGCG could be given since the amount of intervention studies was limited. These studies provided reliable evidence showing that L-theanine and caffeine have clear beneficial effects on sustained attention, memory, and suppression of distraction. Moreover, L-theanine was found to lead to relaxation by reducing caffeine induced arousal.
... For example, a previous study on EGP performed the elevated plus-maze and marble burying test after 30 min, followed by exposure to EF stress (Zhao et al., 2015). Another study performed the STAI test immediately after the attentional tasks (Higashiyama et al., 2011). In this study, not measuring the STAI immediately on the last day of the 8-week arithmetic task might have influenced the S-STAI result according to the subjects' individual stress levels on that day. ...
... The subjects showed relatively high levels of state and trait anxiety, while the scores of BAI and HAM-A showed mild anxiety at baseline evaluation. This discrepancy might be because the STAI and BAI load onto separate factors in factor analysis, suggesting that they represent separate concepts (Higashiyama et al., 2011). Convergent validity between STAI and BAI ranged from 0.47 to 0.64 (Higashiyama et al., 2011), and Pearson's correlation coefficient between STAI and HAM-A was 0.536 for state anxiety and 0.434 for trait anxiety in patients with generalized anxiety disorder (Kennedy et al., 2001). ...
... This discrepancy might be because the STAI and BAI load onto separate factors in factor analysis, suggesting that they represent separate concepts (Higashiyama et al., 2011). Convergent validity between STAI and BAI ranged from 0.47 to 0.64 (Higashiyama et al., 2011), and Pearson's correlation coefficient between STAI and HAM-A was 0.536 for state anxiety and 0.434 for trait anxiety in patients with generalized anxiety disorder (Kennedy et al., 2001). ...
Article
Full-text available
Background The ethanol extract of Gynostemma pentaphyllum Makino leaves (EGP) has been reported recently to have anxiolytic effects on chronically stressed mice models. Purpose We aimed to investigate the efficacy and safety of EGP on anxiety level in healthy Korean subjects under chronic stressful conditions. Study design Double-blind, placebo-controlled trial. Methods This study was conducted with 72 healthy adults who had perceived chronic stress and anxiety with a score on the State-Trait Anxiety Inventory (STAI) from 40 to 60. Participants were randomly assigned to receive either EGP (200 mg, twice a day, N = 36) or placebo (N = 36). All participants were exposed to repetitive loads of stress by performing the serial subtraction task for 5 min every second day during the 8-week intervention. Primary outcome of Trait-STAI and secondary outcomes of State-STAI, total score of STAI, Hamilton Anxiety Inventory (HAM-A), Beck Anxiety Inventory (BAI), blood norepinephrine and adrenocorticotropic hormone (ACTH), salivary cortisol and alpha-amylase, cardiovascular autonomic nervous system (ANS) functional test, and heart rate variability (HRV) test were measured before and after intervention. Results After the 8-week intervention, the EGP significantly lowered the score of the Trait Anxiety Scale of the STAI (T-STAI) by 16.8% compared to the placebo (p = 0.041). The total score on the STAI decreased by 17.8% in the EGP group and tended to improve compared with that of the placebo group (p = 0.067). There were no significant differences in the changes in score of S-STAI, HAM-A, BAI, and other parameters from baseline between the two groups. There was no causal relationship between the ingestion of EGP and adverse drug reactions. Conclusion We found that supplementation with EGP reduced “anxiety proneness” in subjects under chronic psychological stress, as shown by a decrease in the score of T-STAI and the tendency for decrease in the total score of STAI. This result suggests that EGP supplementation can be used as a regimen to safely reduce stress and anxiety; however, more studies are needed to establish the long-term safety and effectiveness.
... Our previous findings indicate that L-theanine, caffeine and their combination improve visual color stimulus discrimination reaction time and increase the P300 event-related potential amplitude in an auditory oddball paradigm (which is an electrophysiological marker of allocation of attention-related neural resources for target stimulus identification and stimulus discrimination [14]) compared to a placebo [15]. Our subsequent analyses also revealed that Ltheanine and caffeine have additive effects in increasing neural resource allocation for stimulus discrimination (as indicated by auditory P300 amplitude) and also in increasing visual color stimulus discrimination [15,16].These findings are compatible with behavioral and electrophysiological findings of many others, suggesting that L-theanine, caffeine and their combination improve cognitive processing, visual stimulus discrimination and possibly visual attention [1,15,16,17,18,19,20]. ...
... Together, these findings do however corroborate our previous findings and findings of others, indicating that L-theanine, caffeine and their combination seem to be associated with faster stimulus discrimination reaction times [1,15,16,17,18,19,20]. ...
Article
Oral intake of L-theanine and caffeine supplements are known to be associated with faster stimulus discrimination, possibly via improving attention to stimuli. We hypothesized that L-theanine and caffeine may be bringing about this beneficial effect by increasing attention-related neural resource allocation to target stimuli and decreasing deviation of neural resources to distractors. We used functional magnetic resonance imaging (fMRI) to test this hypothesis. Solutions of 200 mg of L-theanine, 160 mg of caffeine, their combination or the vehicle (distilled water; placebo) were administered in a randomized four-way crossover design to nine healthy adult males. Sixty minutes after administration, a 20-minute fMRI scan was performed while the subjects performed a visual color stimulus discrimination task. L-theanine and L-theanine-caffeine combination resulted in faster responses to targets compared to placebo (∆ = 27.8 ms, P = .018; and ∆ = 26.7 ms, P = .037 respectively). L-theanine was associated with decreased fMRI responses to distractor stimuli in brain regions that regulate visual attention, suggesting that L-theanine may be decreasing neural resource allocation to process distractors, thus allowing to attend to targets more efficiently. L-theanine-caffeine combination was associated with decreased fMRI responses to target stimuli as compared to distractors in several brain regions that typically show increased activation during mind wandering. Factorial analysis suggested that L-theanine and caffeine seem to have a synergistic action in decreasing mind wandering. Therefore, our hypothesis that L-theanine and caffeine may be decreasing deviation of attention to distractors (including mind wandering), thus enhancing attention to target stimuli was confirmed.
... The evaluations of anxiety are usually conducted by subjective questionnaires. In a study performed by Higashiyama et al. [27], participants were dived into two groups referred to as high and low anxiety propensity group according to the enquiry of manifest anxiety scale. Compared to the placebo group, the intake of L-theanine decreased heart rate (P = 0.001 6), enhanced visual attentional performance (P = 0.000 1), and improved reaction time response among healthy subjects in the high anxiety propensity group (P = 0.001) [27]. ...
... In a study performed by Higashiyama et al. [27], participants were dived into two groups referred to as high and low anxiety propensity group according to the enquiry of manifest anxiety scale. Compared to the placebo group, the intake of L-theanine decreased heart rate (P = 0.001 6), enhanced visual attentional performance (P = 0.000 1), and improved reaction time response among healthy subjects in the high anxiety propensity group (P = 0.001) [27]. ...
Article
Tea (Camellia sinensis) is widely considered to promote feelings of calming and soothing. This effect is attributed to L-theanine (L-γ-glutamylethylamide) in tea, a non-protein amino acid mainly derived from tea leaves. As a naturally occurring structural analogue of glutamate, L-theanine competes for the receptors with glutamate and is able to pass the blood-brain barrier to exert its relaxation effect. This review focuses on the relaxation effect of L-theanine, including animal models and the latest human trials as well as the potential molecular mechanisms regarding neuron stem cells. The biological efficacy of dietary L-theanine in the food matrix has been further discussed in this review in relation to the physiological changes in the gastrointestinal tract and bindings of L-theanine with other food components.
... A convincing body of evidence supports that this substance has several pharmacological functions, including reducing blood pressure in spontaneously hypertensive rats [38] and antagonizing caffeine-induced convulsions [39][40][41] and sleep disturbances [42]. Moreover, this compound has been shown to decrease physical stress in men [43,44] and to suppress anxiety and stress during the premenstrual period in women [45] and anxiety levels in both men and women [46][47][48][49]. The structural similarity of L-theanine to glutamic acid, a neurotransmitter in the brain, has also prompted researchers to investigate its competitive action on the nervous system as a glutaminergic antagonist [50]. ...
... Additionally, the variation in the reaction times confirmed that the L-theanine subjects were as reactive and alert as normal subjects. Previous studies suggest a significant improvement in the reaction time and the occurrence of correct answers in young male subjects with the ingestion of 200 mg of L-theanine [46]. According to an earlier study, the PVT and multiple sleep latency test (MSLT) were most comparable for a sleep and drowsiness assessment [94]. ...
Article
Sleep deprivation is associated with an elevated risk of various diseases and leads to a poor quality of life and negative socioeconomic consequences. Sleep inducers such as drugs and herbal medicines may often lead to dependence and other side effects. l-Theanine (γ-glutamylethylamide), an amino acid naturally found abundant in tea leaves, has anxiolytic effects via the induction of α brain waves without additive and other side effects associated with conventional sleep inducers. Anxiolysis is required for the initiation of high-quality sleep. In this study, we review the mechanism(s), safety, and efficacy of l-theanine. Collectively, sleep studies based on an actigraph, the obstructive sleep apnea (OSA) sleep inventory questionnaire, wakeup after sleep onset (WASO) and automatic nervous system (ANS) assessment, sympathetic and parasympathetic nerve activities, and a pediatric sleep questionnaire (PSQ) suggest that the administration of 200 mg of l-theanine before bed may support improved sleep quality not by sedation but through anxiolysis. Because l-theanine does not induce daytime drowsiness, it may be useful at any time of the day. The no observable adverse effect level (NOAEL) for the oral administration of l-theanine was determined to be above 2000 mg/kg bw/day. Key teaching points: Sleep deprivation-associated morbidity is an increasing public health concern posing a substantial socioeconomic burden. Chronic sleep disorders may seriously affect quality of life and may be etiological factors in a number of chronic diseases such as depression, obesity, diabetes, and cardiovascular diseases. Most sleep inducers are sedatives and are often associated with addiction and other side effects. l-Theanine promotes relaxation without drowsiness. Unlike conventional sleep inducers, l-theanine is not a sedative but promotes good quality of sleep through anxiolysis. This review suggests that l-theanine is a safe natural sleep aid.
... This study explored changes in alpha activity within 60 min of administration of water or 50-mg and 200-mg doses of L-theanine in female participants, four high and four low in trait anxiety, reporting a dose-dependent increase in alpha power with trending towards significance across all participants, but significantly greater in the high anxiety group. Similarly, Higashiyama and colleagues [24] reported significantly elevated alpha activity during rest periods between cognitive tasks in the 60 min following 200-mg L-theanine administration compared to placebo; again, this effect was only apparent for eight participants showing higher trait anxiety. This study failed to observe a concomitant change in subjective anxiety associated with this effect on alpha oscillatory activity. ...
... The outcomes of resting state MEG recordings demonstrated increased alpha oscillatory activity across posterior brain regions after treatment with the L-theanine-based nutrient drink. Consistent with previous research [24,28,30], this effect was apparent only for those higher in trait anxiety. Trait anxiety scores in the high anxiety group ranged from 60th-90th percentile ranks based on Australian adult population norms [67]; as such, this higher anxiety group represents moderate to high levels of trait anxiety. ...
Article
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L-theanine (γ-glutamylethylamide) is an amino acid found primarily in the green tea plant. This study explored the effects of an L-theanine-based nutrient drink on mood responses to a cognitive stressor. Additional measures included an assessment of cognitive performance and resting state alpha oscillatory activity using magnetoencephalography (MEG). Thirty-four healthy adults aged 18–40 participated in this double-blind, placebo-controlled, balanced crossover study. The primary outcome measure, subjective stress response to a multitasking cognitive stressor, was significantly reduced one hour after administration of the L-theanine drink when compared to placebo. The salivary cortisol response to the stressor was reduced three hours post-dose following active treatment. No treatment-related cognitive performance changes were observed. Resting state alpha oscillatory activity was significantly greater in posterior MEG sensors after active treatment compared to placebo two hours post-dose; however, this effect was only apparent for those higher in trait anxiety. This change in resting state alpha oscillatory activity was not correlated with the change in subjective stress response or the cortisol response, suggesting further research is required to assess the functional relevance of these treatment-related changes in resting alpha activity. These findings further support the anti-stress effects of L-theanine.
... Caffeine improves low alertness during long drive [14]. Besides caffeine, Theanine improves attentional performance at a dose of 200 mg/100 ml water [19]. Important to notice, effect of caffeine is shown to be related to the habitual intake levels. ...
... This finding goes in line with the caffeine related improved performance in the Berg's Card Sorting Test (BCST) and simple reaction time tasks and supports previous findings that showed caffeine induced facilitation of attention [32,44] and level of alertness [13,45]. It is also consistent with other previous studies [2,16,19,38] that linked consumption of tea to robust increases in alertness and information processing capacity [4]. As cholinergic mechanisms have been shown to be a necessary condition for memory formation in rats [46], we hypothesize that BT might also be able to influence the level of cholinergic mechanisms in humans, thus improving memory formation [46]. ...
Article
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Background Black Tea is a widely consumed drink in the world. Evidence suggest Black Tea has stimulatory effect on humans. We investigated the effect of Black Tea on cognition using a cognitive test battery. Methods Participants (n = 32) were fasted overnight for 10 h and restrained from caffeine and other stimulant drugs for 14 days prior to participation. We randomly assigned participants into either an experimental (n = 16) or a control (n = 16) group. Experimental group consumed 250 ml of Black Tea (BT) while control group was received equal volume of water (W). Participants were tested on the following cognitive tasks: executive function, sustained attention, memory (memory span, immediate, delayed, working memory) and arithmetic calculation task. Results We found that BT group performed significantly (p < 0.05) faster in the executive function task (BT: M = 1671, SD = 319; W: M = 1935, SD = 372); simple reaction time task (BT: M = 333, SD = 87; W: M = 361, SD = 101), identification of target location in the visual search task (BT: M = 925, SD = 50; W: M = 972, SD = 115). We also showed that BT group forgotten significantly (p < 0.05) lower number of words in the delayed memory recall test (BT: M = 1.12, SD = 0.15; W: M = 1.37, SD = 0.33) and made significantly (p < 0.05) fewer errors in the trail making task (BT: M = 0.31, SD = 1.01; W: M = 1.31, SD = 1.66). Conclusions BT consumption speeded the performance, improved memory, reduced number of errors in the various cognitive tasks. Our results further showed that even in small volume of BT consumption can speed up cognitive processing.
... Detected amounts of GABA and theanine were 0.25 mg and 52 mg, respectively, in shaded white tea, while they were 0.15 mg and 17 mg in Sagara. Knowing that most human mood studies have used higher doses of theanine (for example, 200 mg in Juneja et al. [3] and Higashiyama et al. [23]; and 250 mg in Gomez-Ramirez et al. [24]), the low dose of 52 mg in shaded white tea in this study might have been insufficient. However, one previous study on the effect of theanine consumption on human brain alpha activity found significantly greater and increasing alpha activity after ingestion of 50 mg theanine compared with placebo [25]. ...
Article
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Background Green tea has become renowned for its health benefits. In this study, we investigated the anti-stress effect of two kinds of green tea against a mental stress task load. Methods Warm water, ordinary green tea (Sagara), and shaded white tea, which contains more amino acid components than Sagara, were used as test samples in a randomized cross-over design study. Eighteen students (nine male and nine female) participated in three experimental trials on different days at intervals of seven days. Saliva was collected before beverage intake and after performing the mental stress load tasks. Concentration of chromogranin A (CgA) in the saliva was used as an index of autonomic nervous system activity. Results CgA level increased after the mental tasks, but intake of green tea inhibited this increase; the anti-stress effect was even greater after consumption of shaded white tea. Intake of shaded white tea also lowered Total Mood Disturbance (TMD) score on the Profile of Mood States (POMS); subjects in this condition tended to perform more calculations in the arithmetic task than those in the warm water treatment condition. Conclusions Salivary CgA concentration levels increased after mental stress load tasks, but ingestion of green tea inhibited this increase. This anti-stress effect was larger after the consumption of shaded white tea than after Sagara. Shaded white tea intake also lowered TMD score (POMS) and tended to improve performance on an arithmetic task compared to warm water, suggesting that shaded white tea might also improve mood during and after mental stress load.
... Besides the relaxing effect, theanine shows a much of other beneficial activities, such as improvement in learning ability and attention, reduction of blood pressure, improvement of immune system, reduction of anxiety related to caffeine consumption, weight decrease (Owen et al., 2008;Wang et al., 2010;Higashiyama et al., 2011;Vuong et al., 2011) and enhancement of antitumor efficacy of chemotherapeutic agents (Friedman et al., 2007;Liu et al., 2009). Recently, theanine was even correlated with inhibition of tobacco and nicotine addiction (Yan et al., 2010). ...
Article
Nowadays, consumers appreciate the positive properties of decaffeinated tea for their well-being. During decaffeination process, a very fine tea dust powder is obtained as by-product, which contains the same quantity of bioactives as decaffeinated tea: the antioxidant polyphenols and the amino acid theanine. The aim was to add value to theanine gained from black tea powder dust and to develop theanine-enriched bread. A theanine containing powder was obtained by column separation of decaffeinated tea dust extract and spray-drying using carrier supports. This powder contains also the very polar compounds from decaffeinated tea such as amino acids, sugars and minerals. Breads with 110, 220 and 330 ppm of theanine, respectively, were prepared with the theanine powder. Physical properties, theanine and total polyphenolic content in bread were analysed. Bread and other bakery food serve as good products to add value to bioactive tea dust ingredients.
... Theanine (γ-glutamylethylamide) is the most abundant free amino acid and a kind of unique component in tea tree [4,20]. It has several positive effects, such as making people relaxed [21,22], improving memory and attention [23] and antagonizing with caffeine [24]. Previous studies suggest that theanine is synthesized from glutamic acid and ethylamine derived from decarboxylation of alanine by theanine synthetase (TS), which is highly homologous to glutamine synthetase (GS) [4,25]. ...
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Camellia taliensis is one of the most important wild relatives of cultivated tea tree, C. sinensis. The species extensively occupies mountainous habitats representing a wide-range abiotic tolerance and biotic resistance and thus harbors valuable gene resources that may greatly benefit genetic improvement of cultivated tea tree. However, owning to a large genome size of ~3 Gb and structurally complex genome, there are fairly limited genetic information and particularly few genomic resources publicly available for this species. To better understand the key pathways determining tea flavor and enhance tea tree breeding programs, we performed a high-throughput transcriptome sequencing for C. taliensis. In this study, approximate 241.5 million high-quality paired-end reads, accounting for ~24 Gb of sequence data, were generated from tender shoots, young leaves, flower buds and flowers using Illumina HiSeq 2000 platform. De novo assembly with further processing and filtering yielded a set of 67,923 transcripts with an average length of 685 bp and an N50 of 995 bp. Based on sequence similarity searches against public databases, a total of 39,475 transcripts were annotated with gene descriptions, conserved protein domains or gene ontology (GO) terms. Candidate genes for major metabolic pathways involved in tea quality were identified and experimentally validated using RT-qPCR. Further gene expression profiles showed that they are differentially regulated at different developmental stages. To gain insights into the evolution of these genes, we aligned them to the previously cloned orthologous genes in C. sinensis, and found that considerable nucleotide variation within several genes involved in important secondary metabolic biosynthesis pathways, of which flavone synthase II gene (FNSII) is the most variable between these two species. Moreover, comparative analyses revealed that C. taliensis shows a remarkable expansion of LEA genes, compared to C. sinensis, which might contribute to the observed stronger stress resistance of C. taliensis. We reported the first large-coverage transcriptome datasets for C. taliensis using the next-generation sequencing technology. Such comprehensive EST datasets provide an unprecedented opportunity for identifying genes involved in several major metabolic pathways and will accelerate functional genomic studies and genetic improvement efforts of tea trees in the future.
... Numerous studies have highlighted the effects of L-THE on learning ability and on a multitude of neuroprotective effects ( Table 2) [8]. One specific study, involving administration of L-THE (200 mg/100 mL water), reported profound effects on attention performance as well as on reaction time responses in normal healthy subjects prone to high anxiety [59]. There is also evidence to support its synergistic relationship with caffeine. ...
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Tea has been consumed for thousands of years and is an integral part of people’s daily routine, as an everyday drink and a therapeutic aid for health promotion. Consumption of tea has been linked to a sense of relaxation commonly associated with the content of the non-proteinogenic amino acid theanine, which is found within the tea leaves. The aim of this review article is to outline the current methods for synthesis, extraction and purification of theanine, as well as to examine its potential benefits related to human health. These include improvements in cognitive and immune function, cancer prevention, reduced cardiovascular risk and its potential usefulness as a functional food product.
... Animal studies demonstrated that some natural tea components prolong the sleeping time through the potentiation of GABA A R response [12]. Further, L-theanine, which is present in green tea leaves, displays anxiolytic activity in humans [13]. ...
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Potentiation of γ-amino butyric acid (GABA)-induced GABAA receptor (GABAAR) activation is a common pathway to achieve sedative, sleep-enhancing, anxiolytic, and antidepressant effects. Presently, a three-component test system was established for the identification of novel GABAAR modulating food plants. In the first step, potentiation of GABA-induced response of the GABAAR was analysed by two-electrode voltage clamp (TEVC) for activity on human α1β2-GABAAR expressed in Xenopus laevis oocytes. Positively tested food plants were then subjected to quantification of GABA content by high-performance liquid chromatography with fluorescence detection (HPLC–FLD) to exclude test foods, which evoke a TEVC-response by endogenous GABA. In the third step, specificity of GABAA-modulating activity was assessed by TEVC analysis of Xenopus laevis oocytes expressing the homologous glycine receptor (GlyR). The three-component test was then applied to screen 10 aqueous extracts of food plants for their GABAAR activity. Thus, hop cones (Humulus lupulus) and Sideritis sipylea were identified as the most potent specific GABAAR modulators eliciting significant potentiation of the current by 182 ± 27 and 172 ± 19 %, respectively, at the lowest concentration of 0.5 μg/mL. The extracts can now be further evaluated by in vivo studies and by structural evaluation of the active components.
... A few ingredients that may provide benefits include rhodiola, theanine, and citicoline. Rhodiola may help active women reduce fatigue and may also improve mood as well (100); theanine, often combined with caffeine, has the potential to improve relaxation and attention (101); and citicoline may help to improve memory (102). When evaluating the use of dietary supplements for active women, consideration should be given to the supplement's potential for improving fatigue and targeting memory, attention, and focus (103). ...
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In the United States, women, while having a longer life expectancy, experience a differential risk for chronic diseases and have unique nutritional needs based on physiological and hormonal changes across the lifespan. However, much of what is known about health is based on research conducted in men. Additional complexity in assessing nutritional needs within gender include the variation in genetics, body composition, hormonal milieu, underlying chronic disease, and medication usage, with this list expanding as we consider these variables across the life course. It is clear women experience nutrient shortfalls during key periods of their lives, which may differentially impact their health. Consequently, as we move in to the era of precision nutrition, understanding these sex- and gender-based differences may help optimize recommendations and interventions chosen to support health and weight management. Recently, a scientific conference was convened with content experts to explore these topics from a life-course perspective at biological, physiological, and behavioral levels. This publication summarizes the presentations and discussions from the workshop and provides an overview of important nutrition and related lifestyle considerations across the life course. The landscape of addressing female specific nutritional needs continues to grow; now more than ever, it is essential to increase our understanding of the physiological differences between men and women, and how these physiological considerations may aid in optimizing nutritional strategies to support certain personal goals related to health, quality of life, sleep, and exercise performance among women.
... Juneja et al. (1999) reported that L-Th is also responsible for generation of α-waves in brain which produce relaxation. An increase in alpha electric band was observed within 60 min in a double blind, placebo controlled trial on healthy male university students when given L-Th (200 mg) in a visual attention and rapid audio tasks in repeated measurement design (Higashiyama, Htay, Ozeki, Juneja, & Kapoor, 2011). Another randomized, double blind placebo controlled study revealed that L-Th (400 mg) induced quality sleep with less nocturnal motor activity along with less wake fullness after onset of sleep in ADHD children (Lyon, Kapoor, & Juneja, 2011). ...
Article
L-theanine (L-Th), a non-protein amino acid present in tea, is a valuable nutraceutical product with unique health benefits and used as an additive in food industry. L-Th enhances the umami taste but its use is limited due to its inadequate production. Different extraction approaches from tea shoots, chemical synthesis to microbial transformation have been tried to meet its demand. In vitro, in vivo as well as clinical studies have shown its positive effect in regulating CNS disorders. L-Th has become choice ingredient in CNS active products due to its anti-stress and neuroprotective role in dementias particularly in retrogression of Alzheimer's. L-Th biochemically modulates various anti-neoplastic agents by increasing their bioavailability in tumour cells. The review, is an effort to condense the recent research on L-Th highlighting its biological resource, plausible role in tea plant, production approaches, its physiological role on human health and future prospects.
... Indeed, previous experiments by Higashiyama et al. (2011) found that L-theanine did only cause significant improvement in attention and reaction time in subjects that exhibited a greater degree of (self-reported) anxiety. 55 Similarly, experiments by White et al. analyzing the cognitive effect of NeuroBliss®, an L-theanine based nutrient drink, found that the product did not induce any change in cognitive performance. 56 It did, however, reduce subjective stress response which also correlated with a reduced cortisol response. ...
Article
In general, preparations of coffee, teas, and cocoa containing high levels of polyphenols, L-theanine and other bioactive compounds selectively enhance mood and cognition effects of caffeine. This review summarizes the bioactive components of commonly consumed natural caffeine sources (e.g. guayusa, mate and camellia teas, coffee and cocoa) and analyzes the psychopharmacology of constituent phytochemicals: methylxanthines, polyphenols, and L-theanine. Acute and chronic synergistic effects of these compounds on mood and cognition are compared and discussed. Specific sets of constituent compounds such as polyphenols, theobromine and L-theanine appear to enhance mood and cognition effects of caffeine and alleviate negative psychophysiological effects of caffeine. However, more research is needed to identify optimal combinations and ratios of caffeine and phytochemicals for enhancement of cognitive performance.
... The content of different bioactive constituents of Matcha and other tea formulations such as green tea are reported to be different due to their different cultivation conditions and processing (Komes, Horžić, Belščak, Ganić, & Vulić, 2010). L-theanine, epigallocatechin gallate (EGCG), caffeine, vitamins, and amino acids are the major components of Camellia sinensis, and it has been reported, in both in vitro and human studies, that each single component has beneficial functions, such as tumor growth suppression and mood enhancing effects (de Souza, Gambeta, Stern, & Zanoveli, 2018;Higashiyama, Htay, Ozeki, Juneja, & Kapoor, 2011;Schröder et al., 2019;Smith, 2002). Notably, Matcha tea is a suspension of the Matcha tea powder containing all the components of the Camellia sinensis leaves and is expected to have various physiological effects such as blood flow improvement, mood improvement, and skin whitening in humans (Dietz, Dekker, & Piqueras-Fiszman, 2017). ...
Article
Matcha is thought to be beneficial for brain functions; however, only a few scientific studies have shown the effects of Matcha tea powder on psychiatric behavior. Here, we evaluated the anxiolytic activity of Matcha tea powder, and its hot water extract (CSW) and ethanol extract (CSE) in mice, using the elevated plus maze test. Oral administration of Matcha tea powder and CSE exerted anxiolytic effects. CSE was further fractionated into hexane soluble (CSEH), ethyl acetate soluble (CSEE) and water soluble (CSEW) fractions. Among the fractions, CSEE and CSEH exerted anxiolytic effects. Moreover, SCH23390, a dopamine D1 receptor blocker, and WAY100135, an antagonist of the serotonin (5-hydroxytryptamine: 5-HT) 1A receptor, prevented Matcha tea powder and CSEE from exerting their anxiolytic effects. These results suggest that Matcha tea powder exerts anxiolytic effect through the activation of the dopaminergic and serotonergic systems.
... One drink that is used during competition and in practice by the members of several professional LoL teams is AI Reload (Reload). Active ingredients in Reload with the potential to affect cognition and/or gaming performance include caffeine and L-theanine (alone and in combination) [12][13][14], phosphatidylserine [15], Nicotinamide Adenine Dinucleotide [in the reduced form as NADH] [16], alpha-glycerylphosphorylcholine (alpha-GPC) [17], and L-Carnitine [18], though studies using this supplement have yet to be performed. ...
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To examine the cognitive and physical changes associated with consuming an energy drink concurrent to video gaming, we examined a convenience sample of nine elite League of Legends (LoL) e-sport players (21 ± 2 y, BMI 25.6 ± 3.4 kg/m 2) consuming an energy drink (Reload TM) or placebo (Placebo) in a randomized, double-blind, placebo-controlled cross-over trial. Participants completed the same test battery prior to treatment consumption and after playing each of three competitive LoL games. Primary outcomes included measures of attention (Erikson Flanker Test), reaction time (Go/No-Go test) and working memory (n-back test). Secondary outcomes examined fatigue (hand grip strength and finger tap speed). Statistical analysis was performed by repeated-measures analysis of variance (RM-ANOVA) and reported as the mean (standard deviation [SD]) or mean change (95% confidence interval [CI]). Participants reported sleeping 8.1 (1.2) h/night, playing LoL 10.3 (2.1) h/d, playing other video games 1.8 (2.8) h/d, and exercising 4.2 (1.7) times per week. Overall, we observed no significant time, group, or group-by-time interactions for any measured performance index with the exception of a significant improvement for the n-back test, where the Reload group demonstrated a significant within-group improvement: Reload [−171 ms (95% CI, −327.91, −14.09), p < 0.004], Placebo [−92 ms (95% CI, −213.63, 29.63)]. However, no between-group differences were noted (38.50 ms, 95% CI, −141.89, 64.89, p = 0.803). Our findings suggest that elite eSport athletes do not demonstrate a mental or physical improvement in performance relative to the treatment supplement or indices measured in this study.
... To our knowledge, the present study is the first to examine the effects of l-theanine-caffeine combination on overall cognition using a standardized validated test battery such as the NIH Cognition Toolbox. However, the improvements we observed in overall cognition composite of NIH Toolbox with l-theanine-caffeine combination is not surprising given that multiple interventional trials and meta-analyses of such trials have suggested that particularly the combination of l-theanine and caffeine seems to improve a variety of cognitive functions [25][26][27]33,36,37 . For instance, Camfield et al. performed a systematic review and meta-analysis of studies that have examined the cognitive effects of the l-theanine-caffeine combination to suggest that intake of a combination of l-theanine and caffeine seems to improve attention switching and intersensory attention in healthy adults 36 . ...
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We examined the acute effects of l-theanine, caffeine and their combination on sustained attention, inhibitory control and overall cognition in boys with attention deficit hyperactivity disorder (ADHD). l-Theanine (2.5 mg/kg), caffeine (2.0 mg/kg), their combination and a placebo were administered in a randomized four-way repeated-measures crossover with washout, to five boys (8–15 years) with ADHD. Functional magnetic resonance imaging (fMRI) was performed during a Go/NoGo task and a Stop-signal task ~ 1 h post-dose. NIH Cognition Toolbox was administered ~ 2 h post-dose. Treatment vs. placebo effects were examined in multi-level mixed-effects models. l-Theanine improved total cognition composite in NIH Cognition Toolbox (p = 0.040) vs. placebo. Caffeine worsened and l-theanine had a trend of worsening inhibitory control (i.e. increased Stop-signal reaction time; p = 0.031 and p = 0.053 respectively). l-Theanine–caffeine combination improved total cognition composite (p = 0.041), d-prime in the Go/NoGo task (p = 0.033) and showed a trend of improvement of inhibitory control (p = 0.080). l-Theanine–caffeine combination was associated with decreased task-related reactivity of a brain network associated with mind wandering (i.e. default mode network). l-Theanine–caffeine combination may be a potential therapeutic option for ADHD-associated impairments in sustained attention, inhibitory control and overall cognitive performance.
... Additionally, the anxiolytic effect of epigallocatechin gallate on mice has been reported (36). Furthermore, a human study described the anxiolytic effect of Ltheanine, which is an important bioactive compound of tea (37). Like tea, coffee is consumed because coffee reduces stress (28). ...
Article
Objective: GABAergic system is a target for various groups of medications including sedatives, anxiolytics, muscle relaxants, antidepressants and antiepileptics. Several foods or food ingredients are able to affect the GABAergic system by the inhibition of the γ-aminobutyric acid (GABA) degrading enzymes including the GABA-transaminase and succinate semialdehyde dehydrogenase. The purpose of this study to investigate the inhibitory effects of tea (Camellia sinensis), coffee (Coffea arabica L.), peppermint (Mentha piperita L.), thyme (Thymus vulgaris L.), and cinnamon (Cinnamomum zeylanicum) on GABA degrading enzymes. Methods: The inhibition of the GABA-T by aqueous extracts of tea (Camellia sinensis), coffee (Coffea arabica L.), peppermint (Mentha piperita L.), cinnamon (Cinnamomum zeylanicum), and thyme (Thymus vulgaris L.) was investigated using a fluorometric microplate enzyme assay. Dose-dependent inhibition of the GABA-degrading enzymes was attained by all the food extracts tested. For determination of the IC50 values of the extracts (± 95 % CI), a linear regression was performed using Origin® (Origin® 2015G von Origin Lab Corporation, Northampton, MA 01060 USA). Results: The aqueous extract of black tea presented the strongest inhibitory activity with an IC50-value (half maximal inhibitory concentration) of 13.0 (11.0-15.3) µg/mL. The tested food extracts were successful in inhibiting the GABA-degrading enzymes even at low concentrations. Conclusion: In conclusion, the selected food extracts could serve as natural inhibitors for GABA-degrading enzymes thus, they could increase the GABA concentration in the brain.
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Meta-analyses of tea consumption and reduced risk of Parkinson's disease have thrown light in the pathway of exploring beneficial properties of tea components. On the basis of dry mass, a typical black or green tea beverage contains approximately 6% of free amino acids, which impart high quality, taste and distinctive aroma to the tea infusion. L-theanine (chemically known as γ-glutamylethylamide) is a non-proteinogenic amino acid of tea that takes part in the biosynthesis of its polyphenols. Recently discovered neuroprotective effects of L-theanine can be attributed to its structural analogy with glutamate, the principal excitatory neurotransmitter in brain. This unique amino acid also bears a potential to ameliorate the pathophysiological changes associated with Parkinson's disease as it displays antioxidant and anti-inflammatory properties, improves motor behavioral abnormalities, increases dopamine availability and may cause a favorable downshift in neurodegeneration due to glutamate excitotoxicity. To gain an explicit understanding of the role of L-theanine, this review article is the first one to focus on its mechanism of neuromodulatory action and to critically evaluate the possibilities of employing this bioactive amide in the forage of anti-Parkinsonian medication. We also hypothesize the idea of L-theanine being a potent natural agent against L-DOPA induced dyskinesia, since long-term reliance on dopamine replacement therapy is linked with elevation in glutamate receptor activity.
Article
l-Theanine (LTA), a non-protein-derived amino acid, is isolated from tea and is used as dietary supplement or beverage ingredient. This study established an enterotoxigenic Escherichia coli (ETEC)-infected mouse model of oxidative stress to examine the antioxidative mechanisms of LTA in vivo. LTA regulated non-enzymatic antioxidative activity and increased catalase (CAT) mRNA expression in non-ETEC-infected mice. In addition, LTA decreased oxidative parameters and the activity and mRNA levels of CAT in ETEC-infected mice. LTA increased superoxide dismutase (SOD) activity and mRNA expression of CuZn-SOD, ECSOD and glutathione peroxidase 1 (Gpx1); it restored MnSOD mRNA levels as well. Our results demonstrate that LTA has antioxidative properties via regulation of non-enzymatic pathways. In addition, LTA protects against superoxide and hydrogen peroxide via SOD or Gpx1 as the first and second defence line. Thus, LTA differentially regulates antioxidative enzymes depending on the dose and pathophysiological conditions through transcription, post-transcriptional and post-translational mechanisms in mice.
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L-Theanine is an important component found in tea and has positive effects on nutrients absorption and transport. However, whether L-theanine can regulate glucose, lipid, and protein metabolism remains unknown. This study aimed to investigate the effects of L-theanine on glucose, lipid, and protein metabolism in male Sprague-Dawley rats and characterize the underlying mechanisms. Compared to the control group, L-theanine increased the contents of hepatic and muscle glycogen, serum total protein (TP), and albumin (Alb), lowered the serum low-density lipoprotein cholesterol (LDL-C) level, decreased the activity of acetyl-CoA carboxylase (ACC), and enhanced carnitine palmitoyl transferase-1 (CPT-1) activity in the liver. Additionally, L-theanine upregulated the mRNA expression of phosphofructokinase (PFKL), CPT-1, insulin receptor (INSR), insulin receptor substrate (IRS), and liver kinase B1 (LKB1) and downregulated the mRNA expression of phosphoenolpyruvate carboxykinase 1 (PCK1), glucose-6-phosphatase catalytic subunit (G6PC), fatty acid synthase (FAS), and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR). Moreover, L-theanine upregulated the expression of PFKL, glycogen synthase 2 (GYS2), ribosomal protein S6 (S6), INSR, IRS, and phosphatidylinositol-4,5-bisphosphate3-kinase (PI3K) proteins; downregulated the expression of FAS, sterol regulatory element binding protein-1c (SREBP-1c), and HMGCR proteins; enhanced the phosphorylation of mammal target of rapamycin (mTOR), ribosomal protein S6 kinase (p70S6K), protein kinase B (AKT), and AMP-activated protein kinase (AMPK); and decreased glycogen synthase kinase 3β (GSK-3β) and ACC1 phosphorylation. Further, 100 mg/kg L-theanine was more effective at eliciting these effects than 200 and 400 mg/kg L-theanine. In conclusion, L-theanine can regulate glucose, lipid, and protein metabolism via insulin and AMPK and their downstream signaling pathways.
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The distinct historical background and tea flavor, including high umami taste and low astringency, make the albino tea plants (Atps) stick out from the tea plant (Camellia sinesnis). The decipherment of genes, enzymes, and metabolites involved in these processes is still significantly lagging, which lays an obstacle for molecular plant breeding and commercialized production. With the popularity of high-throughput omics technology, ‘single level’ or ‘multi-level’-based research theory have emerged as powerful tools for revealing the mechanism of characteristic metabolite accumulation and pigment transformation. Thus, it is pivotal to summarize and introduce these advances in facilitating gene identification of critical pathways in the Atps. In this review, we systematically arranged the history and classification of Atps, detailed their strategies for stress response and the metabolic pattern of L-theanine and catechins. Further, reference the successful examples of model plants, we concentrating on the recent advances in omics technology applied to the Atps. Finally, we prospect the promising development areas of the Atps.
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Many nutraceutical ingredients are available in the market that are found to to improve people's mood and sharpen their attention. Nutraceuticals that affect mood focus on stress management, calmness, and alleviation of depression. These ingredients include botanicals, vitamins, omega-3 fatty acids, and a milk peptide. R-U-VED, a division of Ayush Herbs from Redmond, Washington, US, has introduced JoyLift™, a proprietary Ayurvedic dietary supplement from November 2011, featuring saffron and other mood-enhancing herbs. The dietary supplement also includes ashwagandha, gotu kola, mucuna pruriens, and Indian barberry in addition to saffron. These ingredients are considered to be brain tonics that enhance the nervous system and promote tranquility. Researchers have also demonstrated that saffron can be effective for treating mild to moderate mood disorders.
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L-theanine (γ-Glutamylethylamide) is a non-protein water soluble amino acid (AA) mostly occurred in leaves of Camellia sinensis (green tea). This is a key component of green tea, and is considered as the most abundant form of total amino acids in green tea (i.e. about 50%). L-theanine is an exclusive taste ingredient of tea producing an attractive flavor and aroma in tea. It has worth notice biological effects like antioxidant, growth promoter, immune booster, anti-stresser, hepactoprotective, antitumor, anti-aging, antimicrobial, anti-inflammatory and anti-anxiety activities. It could reduce the oxidative impairment by reducing the synthesis of reactive oxygen species (ROS), oxidative parameters and lipid damage as well as increasing the activity of antioxidant enzymes. The oral ingestion of L-theanine enhanced γδ T-cell proliferation. Therefore, it is being considered an essential compound of green tea’ that has ability to improve immune function. The L-theanine can be used as a potential treatment for hepatic injury and immune-related liver diseases via the downregulation of the inflammatory response through the initiation of nitric oxide (NO) synthesis and glutathione (GSH) production are likely to be critical for the control of hepatic diseases as well as for the improvement of immune function. In addition it could be used as a best natural feed additive with potent anti-stressor via decreasing the levels of corticosterone (CORT), dopamine (DA) and noradrenaline (NA). After systematically reviewed the literature it is noticed that, mostly studies done on mice, pig, human and butterfly; while dietary supplementation studies of L-theanine in animal and poultry especially among broilers is very limited due to less awareness of this amino acid. So, the aim of this review is to encourage the veterinarian and poultry researchers to conduct more research at the molecular level about this amino acid to expose its’ more beneficial effects and its’ mechanism of absorption for potential use of this unique green tea amino acid in poultry nutrition.
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Background The interest in the plant-derived healthy foods, nutraceuticals, functional foods and food supplements is increasing in recent times as potential agents in maintenance of health and the prevention and treatment of diseases. Matcha tea powder is obtained from the leaves of tea plant (Camellia sinensis (L.) Kuntze) grown under specific condition using about 90% shade. As compared to green tea, a hot water extract of tea leaves, matcha is consumed as a whole powder of leaves. Matcha powder is reported to have higher content of some bioactive components such as catechins, theanine and caffeine. In recent years, there is an increased market demand and consumption of matcha as a drink and as a component in various beverages, snacks and other food products. Scope and approach In this review, the available scientific information of the chemical constituents and their analysis and biological activities are critically analyzed. These results may help to understand current status of research on matcha and the gaps which help to guide future research related to evidence based product formulations. Key findings and conclusions Various studies have reported the difference in bioactive compounds in matcha as compared to green tea and other tea formulations. The content and composition were mostly affected by the cultivation and processing techniques. Analysis of marketed samples in various countries have shown the variable content of the bioactive compounds. Thus, there is a need for proper standardization for maintaining the quality. Matcha as a whole, its extract and compounds have shown promising biological activities in in vitro and animal studies. However, comparatively only a few clinical studies are performed, which need future attention. There should also be detailed study regarding matcha-containing foods’ formulation.
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There is increasing evidence that black tea polyphenols contribute to vascular health. We have recently shown that regular ingestion of polyphenol-rich black tea over 6 months results in lower systolic and diastolic blood pressure. However, the time course of these effects remains unclear. Therefore, our objective was to determine if short-term effects of tea on blood pressure could contribute to longer-term benefits of regular tea consumption on blood pressure. Men and women (n = 111) were recruited to a randomised placebo-controlled double-blind parallel designed trial. During a 4-week run-in, all participants consumed 3 cups per day of black tea. Participants then consumed 3 cups over 1 day of either powdered black tea solids containing 429 mg of polyphenols (tea), or a control product matched in flavour and caffeine content but containing no tea solids. The 24 h ambulatory blood pressure and heart rate was measured at the end of the 4-week run-in (baseline) and again during the 24 h intervention period. The 24 h day-time and night-time blood pressures were not significantly different between tea and control (P > 0.05). Baseline-adjusted net effects on mean 24 h ambulatory blood pressure for systolic and diastolic blood pressure were -0.2 mm Hg (95% CI, -1.5 to 1.0), P = 0.72, and 0.0 mm Hg (95% CI, -1.0 to 0.9), P = 0.95, respectively. Heart rate was significantly lower for tea compared to control during the night-time and early-morning periods (-2.0 (95% CI, -3.2, -0.8) bpm, and -1.9 (95% CI, -3.7, -0.2) bpm, respectively; P < 0.05 for both), but not during the day-time. These results suggest that the longer-term benefits of black tea on blood pressure are unlikely to be due to short-term changes.
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Background/Objectives Ingestion of the non-proteinic amino acid l-theanine (γ-glutamylethylamide) has been shown to influence oscillatory brain activity in the alpha band (8–14 Hz) in humans during resting electroencephalographic (EEG) recordings and also during cognitive task performance. We have previously shown that ingestion of a 250-mg dose of l-theanine significantly reduced tonic (background) alpha power during a demanding intersensory (auditory-visual) attentional cueing task. Further, cue-related phasic changes in alpha power, indexing the shorter-term anticipatory biasing of attention between modalities, were stronger on l-theanine compared to placebo. This form of cue-contingent phasic alpha activity is also known to index attentional biasing within visual space. Specifically, when a relevant location is pre-cued, anticipatory alpha power increases contralateral to the location to be ignored. Here we investigate whether the effects of l-theanine on tonic and phasic alpha activity, found previously during intersensory attentional deployment, occur also during a visuospatial task. Subjects/Methods 168-channel EEG data were recorded from thirteen neurologically normal individuals while engaged in a highly demanding visuo-spatial attention task. Participants underwent testing on two separate days, ingesting either a 250-mg colorless and tasteless solution of l-theanine mixed with water, or a water-based solution placebo on each day in counterbalanced order. We compared the alpha-band activity when subjects ingested l-Theanine vs. Placebo. Results We found a significant reduction in tonic alpha for the l-theanine treatment compared to placebo, which was accompanied by a shift in scalp topography, indicative of treatment-related changes in the neural generators of oscillatory alpha activity. However, l-theanine did not measurably affect cue-related anticipatory alpha effects. Conclusions This pattern of results implies that l-theanine plays a more general role in attentional processing, facilitating longer-lasting processes responsible for sustaining attention across the timeframe of a difficult task, rather than affecting specific moment-to-moment phasic deployment processes.
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Aims: Previous studies have shown that heart rate variability (HRV) measurement is useful in investigating the pathophysiology of various psychiatric disorders. The present study further examined its usefulness in evaluating the mental health of normal subjects with respect to anxiety and depressiveness. Methods: Heart rate (HR) and HRV were measured tonometrically at the wrist in 43 normal subjects not only in the resting condition but also during a task (random number generation) to assess the responsiveness. For HRV measurement, high-frequency (HF; 0.15-0.4 Hz) and low-frequency (LF; 0.04-0.15 Hz) components of HRV were obtained using MemCalc, a time series analysis technique that combines a non-linear least square method with maximum entropy method. For psychological evaluation of anxiety and depressiveness, two self-report questionnaires were used: State-Trait Anxiety Inventory (STAI) and Self-Rating Depression Scale (SDS). Results: No significant relation was observed between HR and HRV indices, and the psychological scores both in the resting and task conditions. By task application, HF decreased, and LF/HF and HR increased, and significant correlation with psychological scores was found in the responsiveness to task measured by the ratio of HRV and HR indices during the task to that at rest (task/rest ratio). A positive relationship was found between task/rest ratio for HF, and STAI and SDS scores. Task/rest ratio of HR was negatively correlated with STAI-state score. Conclusion: Decreased HRV response to task application is related to anxiety and depressiveness. Decreased autonomic responsiveness could serve as a sign of psychological dysfunction.
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Recent neuropharmacological research has suggested that certain constituents of tea may have modulatory effects on brain state. The bulk of this research has focused on either L-theanine or caffeine ingested alone (mostly the latter) and has been limited to behavioral testing, subjective rating, or neurophysiological assessments during resting. Here, we investigated the effects of both L-theanine and caffeine, ingested separately or together, on behavioral and electrophysiological indices of tonic (background) and phasic (event-related) visuospatial attentional deployment. Subjects underwent 4 d of testing, ingesting either placebo, 100 mg of L-theanine, 50 mg of caffeine, or these treatments combined. The task involved cued shifts of attention to the left or right visual hemifield in anticipation of an imperative stimulus requiring discrimination. In addition to behavioral measures, we examined overall, tonic attentional focus as well as phasic, cue-dependent anticipatory attentional biasing, as indexed by scalp-recorded alpha-band (8-14 Hz) activity. We found an increase in hit rate and target discriminability (d') for the combined treatment relative to placebo, and an increase in d' but not hit rate for caffeine alone, whereas no effects were detected for L-theanine alone. Electrophysiological results did not show increased differential biasing in phasic alpha across hemifields but showed lower overall tonic alpha power in the combined treatment, similar to previous findings at a larger dosage of L-theanine alone. This may signify a more generalized tonic deployment of attentional resources to the visual modality and may underlie the facilitated behavioral performance on the combined ingestion of these 2 major constituents of tea.
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Many neurocognitive models of anxiety emphasize the importance of a hyper-responsive threat-detection system centered on the amygdala, with recent accounts incorporating a role for prefrontal mechanisms in regulating attention to threat. Here we investigated whether trait anxiety is associated with a much broader dysregulation of attentional control. Volunteers performed a response-conflict task under conditions that posed high or low demands on attention. High trait-anxious individuals showed reduced prefrontal activity and slower target identification in response to processing competition when the task did not fully occupy attentional resources. The relationship between trait anxiety and prefrontal recruitment remained after controlling for state anxiety. These findings indicate that trait anxiety is linked to impoverished recruitment of prefrontal attentional control mechanisms to inhibit distractor processing even when threat-related stimuli are absent. Notably, this deficit was observed when ongoing task-related demands on attention were low, potentially explaining the day-to-day difficulties in concentration that are associated with clinical anxiety.
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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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: 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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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 200 mg of L-theanine dissolved in 100 ml of water resulted in the generation of α-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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Since ancient times, it has been said that drinking green tea brings relaxation. The substance that is responsible for a sense of relaxation, is theanine. Theanine is a unique amino acid found almost solely in tea plants and the main component responsible for the exotic taste of ‘green’ tea. It was found that L-theanine administered intraperitoneally to rats reached the brain within 30 min without any metabolic change. Theanine also acts as a neurotransmitter in the brain and decreased blood pressure significantly in hypertensive rats. In general, animals always generate very weak electric pulses on the surface of the brain, called brain waves. Brain waves are classified into four types, namely α,β,δ and θ-waves, based on mental conditions. Generation of α-waves is considered to be an index of relaxation. In human volunteers, α-waves were generated on the occipital and parietal regions of the brain surface within 40 min after the oral administration of theanine (50–200 mg), signifying relaxation without causing drowsiness. With the successful industrial production of L-theanine, we are now able to supply Suntheanine™ (trade name of L-theanine) which offers a tremendous opportunity for designing foods and medical foods targeting relaxation and the reduction of stress. Taiyo Kagaku Co., Ltd, Japan won the 1998 ‘Food Ingredient Research Award’ for development of Suntheanine™ at Food Ingredients in Europe (Frankfurt). The judges felt it was a particularly well-documented and fascinating piece of research.
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Tea ingredients L-theanine and caffeine have repeatedly been shown to deliver unique cognitive benefits when consumed in combination. The current randomized, placebo-controlled, double-blind, cross-over study compared a combination of L-theanine (97 mg) and caffeine (40 mg) to a placebo on two attention tasks and a self-report questionnaire before, and 10 and 60 min after consumption. The combination of L-theanine and caffeine significantly improved attention on a switch task as compared to the placebo, while subjective alertness and intersensory attention were not improved significantly. The results support previous evidence that L-theanine and caffeine in combination can improve attention.
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There have been relatively few studies on the relationship between recent perceived environmental stress and cognitive performance, and the existing studies do not control for state anxiety during the cognitive testing. The current study addressed this need by examining recent self-reported environmental stress and divided attention performance, while controlling for state anxiety. Fifty-four university undergraduates who self-reported a wide range of perceived recent stress (10-item perceived stress scale) completed both single and dual (simultaneous auditory and visual stimuli) continuous performance tests. Partial correlation analysis showed a statistically significant positive correlation between perceived stress and the auditory omission errors from the dual condition, after controlling for state anxiety and auditory omission errors from the single condition (r = 0.41). This suggests that increased environmental stress relates to decreased divided attention performance in auditory vigilance. In contrast, an increase in state anxiety (controlling for perceived stress) was related to a decrease in auditory omission errors from the dual condition (r = - 0.37), which suggests that state anxiety may improve divided attention performance. Results suggest that further examination of the neurobiological consequences of environmental stress on divided attention and other executive functioning tasks is needed.
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The aim of this study was to compare 50 mg caffeine, with and without 100 mg L-theanine, on cognition and mood in healthy volunteers. The effects of these treatments on word recognition, rapid visual information processing, critical flicker fusion threshold, attention switching and mood were compared to placebo in 27 participants. Performance was measured at baseline and again 60 min and 90 min after each treatment (separated by a 7-day washout). Caffeine improved subjective alertness at 60 min and accuracy on the attention-switching task at 90 min. The L-theanine and caffeine combination improved both speed and accuracy of performance of the attention-switching task at 60 min, and reduced susceptibility to distracting information in the memory task at both 60 min and 90 min. These results replicate previous evidence which suggests that L-theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks.
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The effects of i.p. administered theanine (L-N-ethylglutamine), a constituent of Japanese green tea, on the levels of norepinephrine (NE) and serotonin (5-HT) in the brain of rats with or without coadministration of caffeine were investigated, and compared with those of glutamine.Theanine decreased the NE level, whereas no change was observed with glutamine or caffeine.The decrease of NE induced by theanine was reversed by caffeine. In rats pretreated with pargline, a monoamine oxidase inhibitor, theanine significantly increased the NE level compared with the control. However, it did not enhance the NE levels increased by caffeine. Thus, theanine may decrease the NE levels by releasing this neurotransmitter.Theanine did not alter the levels of 5-HT and 5-hydroxyindoleacetic acid (5-HIAA) in rats pretreated with or without pargyline, indicating that this amide affects neither 5-HT synthesis nor its degradation. Caffeine increased the levels of 5-HT and 5-HIAA in normal rats to similar extents.This effect was depressed by theanine. In rats pretreated with pargyline, the levels of 5-HT and 5-HIAA were not altered by caffeine, and theanine did not modify the outcome. It may be concluded that the action of theanine is related to the possible inhibition of 5-HT release by caffeine. The effect of glutamine on the levels of 5-HT was somewhat different form that of theanine.
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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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Theanine, r-glutamylethylamide, is one of the major components of amino acids in Japanese green tea. Effect of theanine on brain amino acids and monoamines, and the striatal release of dopamine (DA) was investigated. Determination of amino acids in the brain after the intragastric administration of theanine showed that theanine was incorporated into brain through blood-brain barrier via leucine-preferring transport system. The concentrations of norepinephrine, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole acetic acid (5HIAA) in the brain regions were unaffected by the theanine administration except in striatum. Theanine administration caused significant increases in serotonin and/or DA concentrations in the brain, especially in striatum, hypothalamus and hippocampus. Direct administration of theanine into brain striatum by microinjection caused a significant increase of DA release in a dose-dependent manner. Microdialysis of brain with calcium-free Ringer buffer attenuated the theanine-induced DA release. Pretreatment with the Ringer buffer containing an antagonist of non-NMDA (N-methyl-D-aspartate) glutamate receptor, MK-801, for 1 hr did not change the significant increase of DA release induced by theanine. However, in the case of pretreatment with AP-5, (+/-)-2-amino-5-phosphonopentanoic acid; antagonist of NMDA glutamate receptor, the theanine-induced DA release from striatum was significantly inhibited. These results suggest that theanine might affect the metabolism and/or the release of some neurotransmitters in the brain, such as DA.
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The present research investigated the effects of controlled experimental manipulations of stress on biological and psychological reactions. Fifty young adult male volunteers were exposed to a 12-min period of stress induced by the threat of an unavoidable, painful electric shock. A 12-min period without this threat preceded or followed the stress period. Blood was drawn during the 4th and the 12th minute of each period. Anticipatory threat led to significant elevations in the proportions and cytotoxic activity of natural killer (NK) lymphocytes, plasma epinephrine levels, pulse rate, and reported level of tension, and to a reduction in the CD4/CD8 ratios. The no-threat period induced a return to baseline values for epinephrine, pulse rate, and tension, and lower than baseline levels for cytotoxic activity of NK lymphocytes, within a similarly short time span. The findings underline the rapidity with which physiological changes may transpire in the course of a brief and acute period of psychological stress, and the rapidity of their reversal upon relief from the stressor.
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Time-dependent changes of theanine (gamma-glutamylethylamide) and other amino acids in various tissues of rats were investigated during the 24 hrs after theanine administration. When theanine (4 g/kg of body weight) was intragastrically administered to rats, the concentrations of theanine in the serum, liver and brain were significantly increased 1 hr after its administration, and thereafter gradually decreased, but reached the maximum level in the brain after 5 hrs. Theanine in these tissues had completely disappeared 24 hrs after its administration. In contrast, the administration of theanine resulted in the concentrations of theanine, urea, ethylamine and glutamic acid in the urine being significantly enhanced. These results suggest that theanine might be degraded via glutamic acid.
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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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Twenty-eight volunteers were instructed to attend stimuli presented at one side of the computer screen and to ignore stimuli presented at the other side. Both attended and unattended stimulus series consisted of targets (25%) and nontargets (75%) defined on the basis of stimulus shape. Attended targets required a binary choice based on stimulus color. Selective attention led to the expected increase in both midlatency (N2b) and late (P3) brain potential components. Furthermore, selective attention led to increased anticipatory cardiac slowing preceding the target stimulus and to increased primary bradycardia. Correlational analyses revealed a positive relation between the effects of selective attention on N2b amplitude and primary bradycardia suggestive of cortical involvement in the chronotropic control of heart rate.
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The neuroprotective effects of theanine and catechins contained in green tea are discussed. Although the death of cultured rat cortical neurons was induced by the application of glutamic acid, this neuronal death was suppressed with exposure to theanine. The death of hippocampal CA1 pyramidal neurons caused by transient forebrain ischemia in the gerbil was inhibited with the ventricular preadministration of theanine. The neuronal death of the hippocampal CA3 region by kainate was also prevented by the administration of theanine. Theanine has a higher binding capacity for the AMPA/kainate receptors than for NMDA receptors, although the binding capacity in all cases is markedly less than that of glutamic acid. The results of the present study suggest that the mechanism of the neuroprotective effect of theanine is related not only to the glutamate receptor but also to other mechanisms such as the glutamate transporter, although further studies are needed. One of the onset mechanisms for arteriosclerosis, a major factor in ischemic cerebrovascular disease, is probably the oxidative alteration of low-density lipoprotein (LDL) by active oxygen species. The oxidative alterations of LDL were shown to be prevented by tea catechins. Scavenging of *O(2)(-) was also exhibited by tea catechins. The neuroprotective effects of theanine and catechins contained in green tea are a focus of considerable attention, and further studies are warranted.
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Since the Taylor Manifest Anxiety Scale has proven to be such a useful device in the selection of subjects for experimental purposes, a description of the construction of the test and the normative data that have been accumulated in connection with it are presented as of possible interest to other investigators in the field of human motivation.
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This study clarified associations among immune, autonomic, and endocrine activities during mental arithmetic and cold pressor stress tasks in 26 women in the follicular phase. Both tasks decreased CD3+ T cells, CD4+ T cells, and CD19+ B cells, whereas they increased lymphocytes, granulocytes, NK cells, and NK cell activity (NKCA). The mental arithmetic task had a greater impact than the cold pressor task on changes in CD3+ T cells and in NK cells. Cardiovascular reactivity to active stress was associated with increased NK cells and decreased CD3+ T cells. Reduced cortisol levels during passive stress were associated with decreased CD19+ B cells and with increased NK cells. The merits of this study are that it controlled the following factors. Perceived stress during the two tasks was matched; both tasks lasted long enough to elicit high-magnitude responses; and the length of the intervening rest period minimized probable carryover effects between tasks.
Article
We investigated the molecular mechanism underlying the neuroprotective effect of theanine, a green tea component, using primary cultured rat cortical neurons, focusing on group I metabotropic glutamate receptors (mGluRs). Theanine and a group I mGluR agonist, DHPG, inhibited the delayed death of neurons caused by brief exposure to glutamate, and this effect of theanine was abolished by group I mGluR antagonists. Although the administration of glutamate alone decreased the neuronal expression of phospholipase C (PLC)-beta1 and -gamma1, which are linked to group I mGluRs, their expression was equal to the control levels on cotreatment with theanine. Treatment with theanine or DHPG alone for 5-7 days resulted in increased expression of PLC-beta1 and -gamma1, and the action of theanine was completely abolished by group I mGluR antagonists. These findings indicate that group I mGluRs might be involved in neuroprotective effect of theanine by increasing the expression levels of PLC-beta1 and -gamma1.
Article
Except for water, tea is the most widely consumed beverage worldwide, primarily because of its perceived relaxant effects.[1][1]–[3][2] Recently, interest has peaked in one component of green tea, theanine, which was isolated and identified in 1949 by a Japanese scientist.[1][1],[4][3] Its
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Anxiety may worsen outcome in psychotic disorders. We assessed anxiety in 44 acutely psychotic subjects and found a positive association with heart rate and blood pressure. Risperidone treatment reduced anxiety but increased heart rate. We concluded that anxiety may adversely affect cardiovascular status in schizophrenia, but the anxiolytic effect of risperidone is not straightforward.
Article
Although both contain behaviourally significant concentrations of caffeine, tea is commonly perceived to be a less stimulating drink than coffee. At least part of the explanation for this may be that theanine, which is present in tea but not coffee, has relaxing effects. There is also some evidence that theanine affects cognitive performance, and it has been found to reduce blood pressure in hypertensive rats. To study the subjective, behavioural and blood pressure effects of theanine and caffeine administered alone and together, in doses relevant to the daily tea consumption of regular tea drinkers. In a randomised, double-blind, placebo-controlled study, healthy adult participants (n = 48) received either 250-mg caffeine, 200-mg theanine, both or neither of these. They completed ratings of mood, including anxiety, and alertness, and had their blood pressure measured before and starting 40 min after drug administration. Anxiety was also assessed using a visual probe task. Caffeine increased self-rated alertness and jitteriness and blood pressure. Theanine antagonised the effect of caffeine on blood pressure but did not significantly affect jitteriness, alertness or other aspects of mood. Theanine also slowed overall reaction time on the visual probe task. Theanine is a physiologically and behaviourally active compound and, while it is unclear how its effects might explain perceived differences between tea and coffee, evidence suggests that it may be useful for reducing raised blood pressure.
Article
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.
Article
We tested whether dynamic interaction between limbic regions supports a control systems model of excitatory and inhibitory components of a negative feedback loop, and whether dysregulation of those dynamics might correlate with trait differences in anxiety and their cardiac characteristics among healthy adults. Sixty-five subjects received fMRI scans while passively viewing angry, fearful, happy, and neutral facial stimuli. Subjects also completed a trait anxiety inventory, and were monitored using ambulatory wake ECG. The ECG data were analyzed for heart rate variability, a measure of autonomic regulation. The fMRI data were analyzed with respect to six limbic regions (bilateral amygdala, bilateral hippocampus, Brodmann Areas 9, 45) using limbic time-series cross-correlations, maximum BOLD amplitude, and BOLD amplitude at each point in the time-series. Diminished coupling between limbic time-series in response to the neutral, fearful, and happy faces was associated with greater trait anxiety, greater sympathetic activation, and lowered heart rate variability. Individuals with greater levels of trait anxiety showed delayed activation of Brodmann Area 45 in response to the fearful and happy faces, and lowered Brodmann Area 45 activation with prolonged left amygdala activation in response to the neutral faces. The dynamics support limbic regulation as a control system, in which dysregulation, as assessed by diminished coupling between limbic time-series, is associated with increased trait anxiety and excitatory autonomic outputs. Trait-anxious individuals showed delayed inhibitory activation in response to overt-affect stimuli and diminished inhibitory activation with delayed extinction of excitatory activation in response to ambiguous-affect stimuli.
Article
This review summarizes the literature on the association between two dietary components of tea, caffeine and L-theanine, and the psychological outcomes of consumption; it also identifies areas for future research. The studies reviewed suggest that caffeinated tea, when ingested at regular intervals, may maintain alertness, focused attention, and accuracy and may modulate the more acute effects of higher doses of caffeine. These findings concur with the neurochemical effects of L-theanine on the brain. L-theanine may interact with caffeine to enhance performance in terms of attention switching and the ability to ignore distraction; this is likely to be reflective of higher-level cognitive activity and may be sensitive to the detrimental effects of overstimulation. Further research should investigate the interactive effects of caffeine, L-theanine, and task complexity, utilize a range of ecologically valid psychological outcomes, and assess the neuroprotective effects of L-theanine using epidemiological or longer-term intervention studies among individuals at risk of neurodegenerative disease.
Article
Tea is the most widely consumed beverage in the world after water. Tea is known to be a rich source of flavonoid antioxidants. However tea also contains a unique amino acid, L-theanine that may modulate aspects of brain function in humans. Evidence from human electroencephalograph (EEG) studies show that it has a direct effect on the brain (Juneja et al. Trends in Food Science & Tech 1999;10;199-204). L-theanine significantly increases activity in the alpha frequency band which indicates that it relaxes the mind without inducing drowsiness. However, this effect has only been established at higher doses than that typically found in a cup of black tea (approximately 20mg). The aim of the current research was to establish this effect at more realistic dietary levels. EEG was measured in healthy, young participants at baseline and 45, 60, 75, 90 and 105 minutes after ingestion of 50mg L-theanine (n=16) or placebo (n=19). Participants were resting with their eyes closed during EEG recording. There was a greater increase in alpha activity across time in the L-theanine condition (relative to placebo (p+0.05). A second study replicated this effect in participants engaged in passive activity. These data indicate that L-theanine, at realistic dietary levels, has a significant effect on the general state of mental alertness or arousal. Furthermore, alpha activity is known to play an important role in critical aspects of attention, and further research is therefore focussed on understanding the effect of L-theanine on attentional processes.
L-Theanine and caffeine improve task switching but not intersensory attention or subjective alertness Pharmacology and therapeutic uses of theanine
  • S J L Einother
  • V E G Martens
  • J A Rycroft
  • E A G De Bruin
  • B V Sweet
Einother, S. J. L., Martens, V. E. G., Rycroft, J. A., & De Bruin, E. A. (2010). L-Theanine and caffeine improve task switching but not intersensory attention or subjective alertness. Appetite, doi:10.1016/j.appet.2010.01.003. Eschenauer, G., & Sweet, B. V. (2006). Pharmacology and therapeutic uses of theanine. American Journal of Health System Pharmacy, 63(1), 26–30.
Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together
  • P J Rogers
  • J E Smith
  • S V Heatherley
  • C W Pleydell-Pearce
Rogers, P. J., Smith, J. E., Heatherley, S. V., & Pleydell-Pearce, C. W. (2008). Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology (Berl), 195(4), 569-577.