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Effects of L-Theanine on the Release of .ALPHA.-Brain Waves in Human Volunteers.
Abstract
L-Theanine is an amino acid found in green tea leaf and in its infusion, and is known to control excitement caused by caffeine. It is also known that the oral administration of L-theanine to rats results in a decrease of serotonin and increase of catecholamines in their brain. L-Theanine has been confirmed to be safe in animal experiments.
We found recently that oral intake of L-theanine caused a feeling of relaxation among the human volunteers examined. These observations led us to do experiments on the effects of administration of L-theanine on the brain electric waves. Eight female university students were selected as volunteers. Four of them were ranked to be Grade I (the highest anxiety) and the remaining four, Grade V (the lowest anxiety) in an investigation done by the manifest anxiety scale method. A dose of oral administration of 200mg of L-theanine dissolved in 100ml of water resulted in the generation of a-electric waves in the occipital and parietal regions of the brains of the subjects. The emission intensity of α-brain waves (integrated as a function of investigation times and area) was significantly greater in the group of Grade I than that of Grade V.
These results indicate the possibility for L-theanine to be applied to foods and beverages as a new type of functional food ingredient for its relaxation effect.
... Green tea (Camellia sinensis), is one of the most popular beverage drinks consumed worldwide (36)(37)(38). Epidemiological studies suggested that green tea consumption may be associated with several beneficial effects on human health (36)(37)(38). It has been shown to beneficial in the management of several diseases, such as adiposity, metabolic disorders, cardiovascular diseases and cancer (36,38). ...
... Green tea (Camellia sinensis), is one of the most popular beverage drinks consumed worldwide (36)(37)(38). Epidemiological studies suggested that green tea consumption may be associated with several beneficial effects on human health (36)(37)(38). It has been shown to beneficial in the management of several diseases, such as adiposity, metabolic disorders, cardiovascular diseases and cancer (36,38). ...
... Epidemiological studies suggested that green tea consumption may be associated with several beneficial effects on human health (36)(37)(38). It has been shown to beneficial in the management of several diseases, such as adiposity, metabolic disorders, cardiovascular diseases and cancer (36,38). Additionally, green tea has been to shown to exert beneficial effects on an individual's psychological state. ...
Green tea and its polyphenolic compounds have been shown to exert positive effects in individuals with psychological disorders. The protective role of green tea against stuttering or its related consequences, depression, anxiety and stress, were evaluated in adolescents with moderate stuttering (MS). A total of 60 adolescents aged (12-18) years old were enrolled in this study. Patients were classified according to standardized test material Stuttering Severity Instrument, 4th Edition was used to estimate the severity of stuttering; participants were classified into two groups: a normal healthy group (n=30) and a MS group (n=30). The Depression Anxiety Stress Scale and General Health Questionnaire were used to estimate the degree of depression, anxiety and stress as well as general mental health. The physiological profile of stress hormones, as a measure of the response to green tea response, was also measured amongst participants. Adrenal stress hormones cortisol, dehydroepiandrosterone (DHEA), acetylcholine (ACTH), corticosterone and the cortisol:DHEA ratio were assayed. In addition, the constituent green tea polyphenols and their quantities were determined using liquid chromatography analysis. Decaffeinated green tea was administered six cups/day for 6 weeks, and this significantly improved the depression, anxiety, stress and mental health consequences associated with stuttering in adolescents. In addition, increased consumption of green tea significantly reduced elevated levels of adrenal stress hormones; cortisol, DHEA, ACTH and corticosterone, and increased the cortisol:DHEA ratio in the control and adolescents who stuttered. The data showed that drinking six cups of decaffeinated green tea, which is enriched in catechins (1,580 mg) and other related polyphenols, was sufficient to improve the consequences of mental health associated with stuttering in younger aged individuals.
... Juneja et al. reported that alpha waves were generated in the occipital and parietal regions of the brain surface of human participants within 40 min of oral L-theanine administration [16]. Kobayashi et al. found that after a single dose of L-theanine, individuals with higher anxiety emitted significantly stronger alpha brainwaves than did individuals with lower anxiety [18], indicating a greater effect. These electroencephalography (EEG) studies have shown that L-theanine had a direct effect on the brain and relaxed the mind without inducing drowsiness [16,18]. ...
... Kobayashi et al. found that after a single dose of L-theanine, individuals with higher anxiety emitted significantly stronger alpha brainwaves than did individuals with lower anxiety [18], indicating a greater effect. These electroencephalography (EEG) studies have shown that L-theanine had a direct effect on the brain and relaxed the mind without inducing drowsiness [16,18]. ...
... Participants were exposed to taskinduced stress 1 h after consumption of the IP. The results of this study are supported by previous reports of direct effects of L-theanine on alpha waves in the occipital and parietal regions of the brain [14,16,18]. The current study investigated the effects of a single 200 mg dose of AlphaWave Ò L-Theanine. ...
Introduction:
Stress is a complex life occurrence essential for survival and goal achievement but can be damaging in excess. Because of the high prevalence of stress in North America, a safe supplement that effectively reduces stress is in demand. The objective of this study was to investigate the efficacy and safety of AlphaWave® L-Theanine on whole-scalp and frontal alpha power, midline theta power, and salivary cortisol in healthy, moderately stressed adults.
Methods:
This was a randomized, triple-blind, placebo-controlled, crossover study that consisted of two study periods with a 7-day washout. A single dose of AlphaWave® L-Theanine (200 mg) or placebo was administered. To induce stress, a mental arithmetic test (MAT) was administered before and after the dose. Electroencephalogram, salivary cortisol, blood pressure, heart rate, self-reported stress, adverse events, clinical chemistry, and hematology were assessed to evaluate efficacy and safety.
Results:
Increases in heart rate, blood pressure, and self-reported stress and state anxiety indicated that participants experienced stress during the MAT. AlphaWave® L-Theanine led to a greater increase in frontal region and whole-scalp alpha power 3 h post-dose compared to placebo (p ≤ 0.050). Within groups, there were increases in alpha power, at 3 h with AlphaWave® L-Theanine, over the whole recording and during the eyes-open portions (p ≤ 0.048) of the alpha task. The changes in alpha wave activity are supported by greater decreases in salivary cortisol 1 h post-dose (p < 0.001) with AlphaWave® L-Theanine compared to placebo.
Conclusion:
This study was conducted during the SARS-CoV-2 pandemic, which has had a rapid and significant effect on both physical and mental health around the world. A single dose of AlphaWave® L-Theanine significantly increased frontal region alpha power compared to placebo in response to an acute stress challenge. These changes are indicative of relaxation in the brain and suggest a calming response. AlphaWave® L-Theanine was found to be safe and well tolerated by participants.
Trial registration:
ClinicalTrials.gov identifier NCT04706494.
... In humans, L-theanine has been shown to facilitate the generation of alpha waves in the brain that are indicative of a relaxed, awake and alert state, without promoting drowsiness [2,[7][8][9]. L-theanine would also help regulate the physiological parameters usually increased during stressful events (e.g. blood pressure, heart rate, cortisol secretion), which further contributes to the stress-reducing effects [9][10][11][12]. ...
... The main reasons for inclusion were stress-related behavioural signs (hypervigilance, nervousness, fear) in 79% of the cases and inappropriate elimination (45% of the cases) while aggressiveness (24% of the cases) and stress-induced functional/organic signs (mainly changes in feeding or drinking behaviour; 21% of the cases) occurred less often ( Table 1). The median (range) age of onset of undesirable behaviours/signs was 1 (0. [2][3][4][5][6][7][8][9][10][11][12] year with 67% and 15% of the cats starting to show issues before the age of 1 and from adoption, respectively. In 42% of the cats, such behaviours had been stable since their onset, but had worsened over time in another 58% of the cats. ...
... Although no study describing the mechanism of action of L-theanine in cat is available, it is highly likely that it is similar to what was described earlier in laboratory animals (especially, an action on glutamate receptors and release of neuromediators) [4,17,19,21]. More specifically, no sedative effect of L theanine has been previously reported in human, in rats, nor in dogs [2,7,8,13,14] .Therefore we expect that the effects observed in this study are due to a decrease of the stress level (and not to a sedative effect). ...
Background
L-theanine is an aminoacid found in tea leaves which has relaxing effects in humans and animals. It is a structural analogue of glutamate which can bind glutamate receptors. Although the relaxing action of L-theanine has been shown in humans, laboratory animals and dogs, it has never been published in cats. The goal of this open-label, multicentre and prospective trial was to determine whether an L-theanine based oral supplement (Anxitane®, Virbac, France) could attenuate manifestations of stress in cats under field conditions.
Case presentation
Thirty-three privately owned cats presenting signs associated with stress or fear (inappropriate urination/defecation, fear-induced aggressiveness, hypervigilance/tenseness or physical/functional manifestations of stress) for at least 1 month, were included in the study. They were given L-theanine (Anxitane®, 25 mg twice a day) for 30 days and 20 stress-related parameters were scored at Days 0, 15 and 30. The evolution of some parameters was also rated relative to Day 0. All median scores of the 20 parameters were significantly reduced at D30, and 30/33 cats (91%) had a reduced global score at the end of the study, including 21/33 with ≥50% score reduction. The median (IQR) global scores went from 18 (13–23) at D0 to 11 (8–13) at D15 and 5 (3–12) at D30 (p < 0.0001; Friedman test; significant reduction starting from D15). All the stress-related signs were significantly improved compared to D0, according to the owners, especially inappropriate elimination. Tablet palatability was judged good or very good in 94% of cases with spontaneous intake by cats when given by hand or in food. Tolerance was satisfactory as well, and no side effects were reported, so that most owners (27/33; 82%) were satisfied with the product.
Conclusions
Despite the lack of a placebo group, it can be concluded that L-theanine (Anxitane®) helped to improve the undesirable manifestations of stress in cats in as soon as 15 days, though better results could be seen after 30 days of administration. These encouraging results show that L-theanine can help manage stress-related behaviour, but additional trials with a placebo group should be run to confirm this effect.
... L-Theanine (g-glutamylethylamide), an amino acid abundantly and exclusively found in tea leaves, is known to be the active ingredient that induces this calming effect. L-Theanine, produced via an enzymatic fermentation process, induces relaxation within 30 minutes after oral intake by generating a-brain waves, an indication of a relaxed yet alert state of mind [37]. 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]. ...
... A high quality of sleep due to the consumption of L-theanine could be presumed to be due to its effect on relaxation and the modulation of neurotransmitters. A previous human study indicated that the intake of L-theanine resulted in the generation of a-waves (8-13 Hz), the brain waves which represent relax and alert state of mind, within 30-40 minutes in the occipital and parietal regions of the brain [37]. Furthermore, it was found that the ingestion of L-theanine decreased b-waves (higher than 14 Hz), an indication of hyperarousal, and increased a-waves (8-13 Hz), thereby confirming a relaxed state [59]. ...
... Approximately 50%-60% of children with ADHD have sleep problems [71] along with their recognized learning disabilities (10%-30%), language disabilities (30%-50%), and oppositional behaviors (30%-80%). In addition to the L-theanine research confirming the relaxation effect [37,71], memory and learning performance [51,72], neuroprotection [61,73,74], and sleep [56,62,75], a study was conducted at the University of British Colombia in collaboration with The Canadian Center for Functional Medicine in Canada to examine the effect of L-theanine on sleep and brain functions in children with ADHD [76]. ...
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.
... 37 When 50 mg of theanine is ingested, alpha waves appear 40 min later. 38,39 The blood concentration peak of theanine occurs later than that of caffeine; therefore, after ingesting the test food, caffeine's central nervous system stimulative effect would be temporarily greater than that of theanine. This is considered the reason that the sleep onset latency was not shortened in the TC group compared with the caffeine group. ...
... The consumption of theanine is reported to alter neurotransmitters such as dopamine, serotonin, 20 tryptophan, and γ-aminobutyric acid (GABA), 21 suppress the excitotoxicity of glutamate, 17 and induce anxiolysis through the induction of alpha waves. 38 However, how these effects are related to improving sleep is a topic for future research. ...
Energy drinks take advantage of caffeine's effects on wakefulness and performance; however, excessive intake has a negative effect on sleep. Green tea is consumed worldwide and has both a stimulating effect from caffeine and a calming or relaxing effect from theanine. Theanine reduces the excitotoxicity of caffeine. This study evaluated whether theanine improves the sleep quality worsened by caffeine in healthy young women. Sleep latency, sleep time, wake after sleep onset (WASO) time, and the number of WASOs were measured. A crossover study was performed using four treatment groups: theanine (50 mg), caffeine (30 mg), combined theanine and caffeine (TC), and placebo. The sleep stage was determined using electroencephalograms, and cerebral blood flow was measured using near-infrared spectroscopy. The caffeine group showed a significant increase in the WASO time compared with the placebo group; no difference was observed between the theanine or TC group and the placebo group. There were no differences in the sleep-onset latency or number of WASOs between the theanine, caffeine, or TC groups and the placebo group. In combination with theanine, only the caffeine-induced increase in the WASO time was suppressed. Our results suggest that theanine can reduce caffeine's effects on sleep quality.
... Theanine, the most abundant free amino acid in green tea, has been found to relieve stress and have a relaxing effect [22][23][24][25][26]. In addition, arginine, which is the second most abundant free amino acid in Japanese green tea, has an anti-stress effect similar to theanine [27,28]. ...
... Furthermore, it has been reported that theanine's effects on neurotransmitters in the brain, such as dopamine [66], suppress excitation by caffeine [69], improve memory [70], have a high affinity for the glutamine transporter [70], and enact a neurogenic effect [71]. As regards the actions of theanine in humans, a relaxing effect [26], stress reduction [24,25], and a reduction in depression and schizophrenia [72] have been reported. On the other hand, little attention has been paid to the functionality of arginine in green tea, but it has been revealed to have an excellent stress-reducing effect, similar to that of theanine [27,28]. ...
Epidemiological studies have demonstrated that the intake of green tea is effective in reducing the risk of dementia. The most important component of green tea is epigallocatechin gallate (EGCG). Both EGCG and epigallocatechin (EGC) have been suggested to cross the blood–brain barrier to reach the brain parenchyma, but EGCG has been found to be more effective than EGC in promoting neuronal differentiation. It has also been suggested that the products of EGCG decomposition by the intestinal microbiota promote the differentiation of nerve cells and that both EGCG and its degradation products act on nerve cells with a time lag. On the other hand, the free amino acids theanine and arginine contained in green tea have stress-reducing effects. While long-term stress accelerates the aging of the brain, theanine and arginine suppress the aging of the brain due to their anti-stress effect. Since this effect is counteracted by EGCG and caffeine, the ratios between these green tea components are important for the anti-stress action. In this review, we describe how green tea suppresses brain aging, through the activation of nerve cells by both EGCG and its degradation products, and the reductions in stress achieved by theanine and arginine.
... Contrastingly, Kobayashi et al. [53] reported that the anxiety group did not show alpha waves at 50 mg of theanine; however, the high anxiety group did. Our study did not investigate mental status; however, it was assumed that the participants were experiencing stress. ...
... Theanine acts as a partial agonist to the N-methyl-D-aspartate receptor, a glutamine receptor [56]. Kobayashi et al. measured human alpha waves and found that the alpha wave, an index of relaxation, did not appear at 50 mg, and that 200 mg was required to see an effect [53]. This study used 50 mg of theanine; thus, it is possible that there was no relaxing effect. ...
Matcha, a type of green tea, has a higher amino acid content than other types of tea. We previously examined the ability of matcha to improve cognitive function in older adults and determined that continuous matcha intake improves attention and executive function. This study aimed to compare the effects of matcha and caffeine and clarify the differences between these effects. The study was registered at the University Hospital Medical Information Network (UMIN000036578). The effect of single and continuous intake was compared, and the usefulness of continuous intake was evaluated under the stress condition. The Uchida–Kraepelin test (UKT) was used to induce mild acute stress, and the Cognitrax was used to evaluate cognitive function. A single dose of caffeine improved attentional function during or after stress loading. The reduced reaction time in the Cognitrax, observed following a single dose of matcha, was likely due to caffeine. The matcha group showed an increase in the amount of work after continuous intake, whereas the caffeine group only showed an increase in the amount of work for the UKT after a single dose. Ingesting matcha with caffeine improves both attention and work performance when suffering from psychological stress compared with caffeine alone.
... Effective for treating anxiety-related behaviors without causing any side effects Araujo et al. (2010) L-theanine (2 and 4 mg/kg) for the stressed mice Ameliorated chronic stress-induced disorders Tian et al. (2013) 4-week L-theanine intake (200 mg/day) on healthy adults Ameliorated stress-related ailments and cognitive impairments Hidese et. al., 2019) Oral administration of L-theanine (200 mg) on the students Increased α-brain wave activity in the occipital and parietal regions of the brains Kobayashi et al. (1998) Oral intake of 200 mg L-theanine on the healthy participants with induced high-stress Attenuated the rise in heart rate, salivary immunoglobulin A responses and blood pressure ...
... After 30 min, significantly increased α-brain wave activity in the occipital and parietal regions of the brains was detected in both groups using electroencephalography (EEG). The emission intensity of α-brain wave in the high-anxiety group was greater than that of low-anxiety group (Kobayashi et al., 1998). To investigate this effect at more realistic dietary levels of L-theanine, EEG was measured at 0, 45, 60, 75, 90 and 105 min after ingestion of 50 mg L-theanine in the healthy young participants (n = 16), who were resting with their eyes closed during EEG recording. ...
With the aging of the population and the growing pressure of social competition, brain-related neurodegenerative diseases and mental disorders increasingly affect our quality of life and place a huge burden on health systems around world. L-theanine is a unique non-protein amino acid from tea leave, and now commercially available as a safe food ingredient in the market. This review summarizes the studies on the effects of L-theanine on various mental and brain conditions, including mental stress, anxiety, insomnia, depression, poor learning ability and memory, neurodegenerative diseases, and discusses its potential application in functional foods for brain health.
... L-theanine is a unique amino acid in tea leaves and is known to affect central nervous system, such as sedation, anti-anxiety and modulation of neurotransmitter activities [8][9][10][11] . Recent studies showed that L-theanine had neuroprotective effects on injured neurons and could improve learning and memory functions in the developing rat brain [12][13][14][15] . ...
... In vitro study, isoflurane inhibited the produce and release of glutamate in nerve terminals, increased the uptake of glutamate in astrocytes and neurons, caused glutamate transmission inhibition and ultimately leading to neurotoxicity [32][33][34][35] . L-theanine is a structural analog of excitatory neurotransmitter glutamate and glutamine, which could bind to glutamate receptors and block the reuptake of glutamate, and thus inhibited the excitatory neurotoxicity of glutamate in brain 9,10,21) . By inhibiting glutamine transporters, L-theanine protected neurons and astroglia from excitatory neurotoxicity of glutamate in rat brain 8,9) However, the neuroprotective effect of L-theanine on central neural system is still not fully understood, especially on NSC and its underline mechanism. ...
The neurodevelopmental toxicity of isoflurane has been proved by many studies, which makes it essential to explore the underline mechanisms and search for protective agents to attenuate its neurotoxcity. Accumulating evidence showed that L-theanine had neuroprotective effects on injured neurons and the developing brain. The present study was designed to investigate whether L-theanine could attenuate isoflurane-induced damage in neural stem cells and cognitive impairment in young mice, and to discuss the role of Akt/GSK-3β signaling pathway in this process. Multipotential neural stem cells (NSCs) and C57BL/6J mice were treated with either gas mixture, isoflurane, or L-theanine 30 min prior to isoflurane exposure, respectively. NSC viability was detected by CCK-8 assay. NSC proliferation and apoptosis were assessed by immunofluorescence and TUNEL assay, respectively. The levels of cleaved caspase-3 and p-Akt and p-GSK-3β in NSCs were tested by Western blotting. Cognitive function of mice was tested by Morris Water Maze at postnatal day (P) 30-35. The results indicated that isoflurane exposure inhibited NSC viability and proliferation, promoted NSC apoptosis as well as increased caspase-3 activation and down-regulated the expressions of p-Akt and p-GSK-3β in NSCs, and that isoflurane exposure on neonatal mice would induce late cognitive impairment. Pretreatment with L-theanine could attenuate isoflurane-caused damage in NSCs and cognitive deficits in young mice. Addinonally, the protective effects of L-theanine on isoflurane-injured NSCs could be reversed by Akt inhibitor Triciribine. Our data showed that pretreatment with L-theanine eliminated the NSC damage and cognitive impairment induced by isoflurane exposure, and that the neuroprotective effect of L-theanine was associated with the Akt/GSK-3β signaling pathway.
... Acute administration of the green tea polyphenol epigallocatechin gallate reduced subjective stress and increased α, β and θ wave activity in healthy young volunteers (48) . There is evidence of relaxant properties of other tea components from human EEG activity (49,50) . Two hundred milligrams of the green tea amino acid L-theanine, but not 50 mg, led to increased α-wave activity in the occipital and parietal regions of the brain within 40 min of ingestion when administered to resting participants. ...
... These include multivitamins, caffeine, n-3 fatty acids glucose and flavanols (including from tea and cocoa). Each is dealt with in detail in (49) and covered in the following sections. ...
Effective pharmaceutical treatments for age-related cognitive decline have proved elusive. There is, however, compelling evidence that nutritional status and supplementation could play crucial roles in modifying the expression of cognitive change through the lifespan. Subjective memory impairment and mild cognitive impairment can be harbingers of dementia but this is by no means inevitable. Neurocognitive change is influenced by a variety of processes, many of which are involved in other aspects of systemic health, including cardiovascular function. Importantly, many of these processes are governed by mechanisms which may be modified by specific classes of bioactive nutrients. There is increasing, converging evidence from controlled trials that nutritional interventions can improve mood and cognitive function in both clinical and healthy populations. Specific examples include selected botanical extracts such as the flavonoids. Some nutritional supplements (e.g. broad-spectrum micronutrient supplementation) appear to support improved cognitive function, possibly through redressing insufficient nutrient status (i.e. suboptimal but above the threshold for frank deficiency). Recent mechanistic research has unveiled physiologically plausible, modifiable, cognition-relevant targets for nutrition and nutraceuticals. These include processes involved in both systemic and central vascular function, inflammation, metabolism, central activation, improved neural efficiency and angiogenesis. The advent and development of human neuroimaging methodology have greatly aided our understanding of the core central mechanisms of cognitive change. Different imaging modalities can provide insights into modifiable central mechanisms which may be targeted by bioactive nutrients. The latter may contribute to slowing age-related decline through supporting neurocognitive scaffolding mechanisms.
... These are an indicator for relaxed physical, awake and alert, and mental condition. Also, these waves are one kind of brain waves revealed either by magnetoencephalography or electroencephalography and mostly created by the occipital lobe through wakeful relaxation with closed eyes [153]. It can be concluded that Ltheanine administration in an average of 50-200 mg can exert a relaxation impact. ...
... Regular or moderate consumption of green tea is safe [223], but the consumption of high levels ranging from 10 to 29 mg/kg/day of the extract derived from green tea causes liver toxicity in humans [224]. Up to present, the side effects of L-theanine in humans are yet to discover [225]; L-theanine showed no somnolence in humans [153]. Despite many documented benefits of consuming green tea and using its extracts, there are certain reports which alarm only limited dosage of green tea as recommended. ...
Green tea (Camellia sinensis) is a famous herb, and its extract has been extensively used in traditional Chinese medicinal system. In this context, several studies have revealed its health benefits and medicinal potentialities for several ailments. With ever increasing scientific knowledge, search for safer, potential and novel type of health-related supplements quest, scientists are re-directing their research interests to explore natural resources i.e. medicinal herbs/plant derived compounds. Green tea consumption has gained a special attention and popularity in the modern era of changing lifestyle. The present review is aimed to extend the current knowledge by highlighting the importance and beneficial applications of green tea in humans for safeguarding various health issues. Herein, we have extensively reviewed, analyzed, and compiled salient information on green tea from the authentic published literature available in PubMed and other scientific databases. Scientific literature evidenced that owing to the bioactive constituents including caffeine, L-theanine, polyphenols/ flavonoids and other potent molecules, green tea has many pharmacological and physiological functions. It possesses multi-beneficial applications in treating various disorders of humans. This review also provides in-depth insights on the medicinal values of green tea which will be useful for researchers, medical professionals, veterinarians, nutritionists, pharmacists and pharmaceutical industry. Future research emphasis and promotional avenues are needed to explore its potential therapeutic applications for designing appropriate pharmaceuticals, complementary medicines, and effective drugs as well as popularize and propagate its multidimensional health benefits.
... In fact, neurotransmitters are affected around 20 min after the ingestion of L-theanine. Tryptophan is converted into serotonin and tyrosine into dopamine [103][104][105][106]. L-theanine was found to increase dopamine release and concentration [107][108][109]. Moreover, it was found that L-theanine increases serotonin and GABA concentrations in striatum, hippocampus, and hypothalamus. ...
... This has been associated with suppression of visual distracting information and increased wakeful relaxation. In stress situations and attention task performance, it was observed that L-theanine increased background-related α-activity, which can be transferred to an improved alert mental state and better performance regarding accuracy level and reaction time [18,51,87,107,116,117]. Gomez-Ramirez et al. (2007) reported that an increase of task-related α-activity and a decrease of background-related α-brainwave activity result in an improvement of selective attention [116]. ...
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.
... Classified into four types α, β, δ and θ waves, these waves potentially act as indicators of continuous electrical activity inside the brain as determined by electroencephalogram (EEG), which effectively measures electrical activity/impulses through electrodes attached to the scalp [5]. Several studies have shown that L-THE intake (50-200 mg) significantly increases the pattern intensity of α-wave production in the different areas of the cerebral cortex without causing drowsiness due to unchanged θ-waves [5,8,52]. An increase in α-waves in the cerebral cortex has been proposed as an index of an increased relaxed but alert mental state [8,53]. ...
... [19] α-Wave production Administration of L-THE (200 mg) in 8 females enhanced the generation of α-wave production. [52] Relaxation Administration of L-THE (200 mg) may increase relaxation under resting conditions. [58] Relaxation Administration of L-THE (200 mg) resulted in a reduction in heart rate and salivary immunoglobulin A (s-IgA) in response to an acute stress task. ...
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.
... Changes in brain alpha oscillatory activity using electroencephalography (EEG) have also been studied as correlates of L-theanine's potential anti-stress effects, using resting state recordings, and cognitive enhancing effects, using task-related recordings. The first study to report changes in human brain activity associated with L-theanine administration described changes in alpha oscillatory activity (8)(9)(10)(11)(12)(13) Hz) during a resting state in scalp electrodes over parietal and occipital regions [27,28]. 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. ...
... 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. ...
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.
... However, they collected blood at 0, 1, 2, 5, 8, 16, and 24 h, and considering that a very high dose of L-theanine (4000 mg/kg) was administered, the Tmax may have been achieved earlier, resulting in the delayed disappearance of L-theanine. For sleep-improving effects, Ltheanine supplements are often taken before sleep, and Kobayashi and Nagato (1998) reported that Ltheanine takes approximately 30 min to produce its effect. Therefore, it is necessary to observe the changes in the blood concentration of L-theanine within 1 h after administration. ...
L-theanine, an amino acid component of the tea leaves of Camellia sinensis, is sold in Japan as a supplement for good sleep. Although several studies in humans and mice have reported the effects of L-theanine on brain function, only a few reports have comprehensively clarified the disposition of theanine administered to mice and its effects on concentrations of other blood amino acids. In this study, we aimed to determine the changes in the blood levels of L-theanine administered to mice and amino acid composition of the serum. L-theanine were administered to four-week-old Std-ddY male mice orally or via tail vein injection. L-theanine and other amino acids in serum prepared from blood collected at different time points post-dose were labeled with phenylisothiocyanate and quantified. The serum concentration of orally administered L-theanine peaked 15 min after administration. The area under the curve for tail vein injection revealed the bioavailability of L- theanine to be approximately 70%. L-theanine administration did not affect any amino acid levels in the serum, but a significant increase in the peak area overlapping the Gly peak was observed 30 min after administration.
L-theanine administered to mice was rapidly absorbed and eliminated, suggesting that taking L-theanine as a supplement is safe without affecting its own levels or serum levels of other amino acids. However, considering that Gly, similar to L-theanine, is used as a dietary supplement for its anxiolytic effects and to improve sleep, determining the effects of L-theanine administration on Gly is important and needs further research.
... Since theanine is structurally similar to glutamic acid and is taken into the brain through the blood-brain barrier [2], its function in the brain has been studied. For example, it has been reported that theanine has a relaxing effect, as alpha waves have been observed to significantly increase in the brain after its ingestion [3]. In addition, animal experiments and clinical studies in humans have shown that theanine offers excellent stress-relieving effects [4][5][6][7][8][9]. ...
Group rearing is a common housing condition, but group-housed older mice show increased adrenal hypertrophy, a marker of stress. However, the ingestion of theanine, an amino acid unique to tea leaves, suppressed stress. We aimed to elucidate the mechanism of theanine’s stress-reducing effects using group-reared older mice. The expression of repressor element 1 silencing transcription factor (REST), which represses excitability-related genes, was increased in the hippocampus of group-reared older mice, whereas the expression of neuronal PAS domain protein 4 (Npas4), which is involved in the regulation of excitation and inhibition in the brain, was lower in the hippocampus of older group-reared mice than in same-aged two-to-a-house mice. That is, the expression patterns of REST and Npas4 were found to be just inversely correlated. On the other hand, the expression levels of the glucocorticoid receptor and DNA methyltransferase, which suppress Npas4 transcription, were higher in the older group-housed mice. In mice fed theanine, the stress response was reduced and Npas4 expression tended to be increased. These results suggest that Npas4 expression was suppressed by the increased expression of REST and Npas4 downregulators in the group-fed older mice, but that theanine avoids the decrease in Npas4 expression by suppressing the expression of Npas4 transcriptional repressors.
... Following the overall analysis, subgroup analysis according to the participants' backgrounds was conducted. Nobre et al. [19] and Kobayashi et al. [22] examined the relaxation effects of 50 mg theanine; the former observed the participants relaxing, but the latter did not. A clear difference between these studies is the subject background. ...
L-theanine (theanine), one of the ingredients of green tea, had been proven to have anti-anxiety, anti-stress, memory, cognitive, and sleep improvement effects in most clinical trials. However, these effects have shown efficacy at a dose of 200–400 mg of theanine a day. In this study, we explored the sleep-improving effects of a lower dose (100 mg/day) of theanine. A double-blind, randomized crossover study was conducted on 25 middle-aged and older males. Participants were randomly assigned to Groups A and B. Group A took theanine first, and Group B took theanine later in the intervention period. The participants took theanine/placebo for one week. Electroencephalogram (EEG) parameters were measured with a monitoring device during sleep, and subjective sleep quality after waking up was evaluated using a questionnaire. Following the statistical analysis between interventions, subgroup analyses according to the participants’ background information were conducted on the representative sleep parameters of non-REM sleep, REM sleep, and wakefulness. Of the 25 participants, three withdrew from this study. In the sleep analysis, there was no significant difference in all sleep parameters between the theanine and placebo periods. In particular, the difference in the percentage of nonREM sleep in stage 2 per sleep duration was not significant (p = 0.053). However, subgroup analysis of the results showed that the percentage of non-REM sleep in stage 2 in groups aged <50 years was higher in theanine than that of the placebo, and in groups with green tea consumption habit of <3 to 4 days per week (p = 0.018, 0.048). The intake of 100 mg/day of theanine does not have an effect on sleep improvement. However, subgroup analyses showed that theanine had an improved effect in stage 2 non-REM sleep according to age and green tea consumption habit.
... Using magnetoencephalography, participants who were naturally more anxious were found to show an increase in alpha oscillatory activity, i.e. lower-frequency brainwaves indicating relaxed wakefulness [71]. Several other studies have reported increased alpha brain wave activity in humans following theanine in different dosages [72,73]. How this effect is mediated is unknown. ...
The available evidence, which derives from studies investigating mechanistic effects of tea, research on animal models as well as epidemiological studies and intervention trials in humans, suggests that compounds contained in tea may have the potential to aid in the prevention of depression or in its treatment as an addition to established therapies. A wide range of potentially antidepressive biological activities of tea components have been reported. However, the mechanisms of tea phytochemicals possibly capable of decreasing the risk of depressive symptoms are complex, multifaceted and not well understood. Potent pharmacological effects on circumscribed neurobiological systems may be produced not by individual tea components but rather by the synergistic action of various compounds on multiple pathophysiological mechanisms involved in depression. While epidemiological studies have generally demonstrated beneficial effects of tea consumption on mood and depressive symptoms, cross-sectional studies are unable to prove a cause-effect relationship. If positive effects on mood could be firmly established, tea drinking could support mental health. However, the moderate antidepressive effects observed in healthy people are not necessarily indicative of possible clinical effects in major depressive disorder. Randomized controlled intervention studies are needed to establish a causal relationship between bioactive compounds in tea and depression.
... LTA accounts for 1% to 2% of the weight of dry tea leaves. 200 mg of LTA can induce relaxation by producing α-waves within 30 minutes in the brains of volunteers after oral administration, leaving people in a relaxed state without causing drowsiness (Kanari Kobayashi, Nagato, Aoi, Juneja, Kim, Yamamoto, and Sugimot 1998). LTA shows a variety of physiological functions, including improving cognition, enhancing immunity, reducing psychological stress and regulating glucose, lipid and protein metabolism (Jang et al. 2012;Li et al. 2016;Lin et al. 2020;Lopes Sakamoto et al. 2019). ...
Sleep disorders have received widespread attention nowadays, which have been promoted by the accelerated pace of life, unhealthy diets and lack of exercise in modern society. The chemical medications to improve sleep has shown serious side effects and risks with high costs. Therefore, it is urgent to develop efficient nutraceuticals from natural sources to ensure sleep quality as a sustainable strategy. As the second most consumed beverage worldwide, the health-promoting effects of tea have long been widely recognized. However, the modulatory effect of teas on sleep disorders has received much less attention. Tea contains various natural sleep-modulating active ingredients such as L-theanine (LTA), caffeine, tea polyphenols (TPP), tea pigments, tea polysaccharides (TPS) and γ-aminobutyric acid (GABA). This review focuses on the potential influence and main regulating mechanisms of different tea active ingredients on sleep, including being absorbed by the small intestine and then cross the blood-brain barrier to act on neurons in the brain as neurotransmitters, manipulating the immune system and further affect sleep-wake cycle by regulating the levels of cytokines, and controlling the gut microbes to maintain the homeostasis of circadian rhythm. Current research progress and limitations are summarized and several future development directions are also proposed. This review hopes to provide new insights into the future elucidation of the sleep-regulating mechanisms of different teas and their natural active ingredients and the development of tea-based functional foods for alleviating sleep disorders.
• Highlights
• • Natural sleep-modulating active ingredients in tea have been summarized.
• • Influences of drinking tea or tea active ingredients on sleep are reviewed.
• • Three main regulating mechanisms of tea active ingredients on sleep are explained.
• • The associations among nervous system, immune system and intestinal microbiota are investigated.
• • The potential of developing delivery carriers for tea active ingredients is proposed.
... An analysis of free amino acids detected large amounts of theanine and glutamic acid. Theanine enhances the flavor of other umami components (Narukawa et al., 2008) and has also been reported to improve sleep and relaxation (Kobayashi et al., 1998;Ozeki et al., 2004). Glutamic acid is regarded as an umami component of tea. ...
The lactic acid bacteria involved in fermentation and components in the tea leaves of Awa-bancha, a post-fermented tea produced in Naka, Kamikatsu, and Miyoshi, Tokushima, were investigated in the present study. Lactic acid bacteria were isolated from tea leaves after anaerobic fermentation and identified by multiplex PCR targeting of the recA gene and 16S ribosomal RNA gene homology. Lactiplantibacillus pentosus was the most frequently isolated species in Naka and Kamikatsu and Lactiplantibacillus plantarum in Miyoshi. In the phylogenetic tree based on the dnaK gene, L. pentosus isolated from Awa-bancha was roughly grouped by the production area and producer. The bacterial flora after anaerobic fermentation was dominated by Lactiplantibacillus spp. for most producers, and the compositions of samples from each producer varied. Organic acids, free amino acids, and catechins were analyzed as components related to the flavor of Awa-bancha. These components were unique to each producer. The present results revealed diversity in the lactic acid bacteria and flavor of Awa-bancha that depended on the producer.
... As it is a natural analog of glutamate and glutamine, it has been shown to have a strong affinity for the glutamine transporter inhibiting glutamine uptake, thereby inhibiting excitatory neurotransmission release [102]. Electroencephalography data following intake of 50-250 mg of L-THE shows an increase in alpha waves in the brain, which indicates a state of relaxation [103,104]. Additionally, L-THE has been shown to be effective in reducing blood pressure increases following a mental task or from the effects of caffeine consumption [105,106]. ...
Functional beverages can be a valuable component of the human diet with the ability to not only provide essential hydration but to deliver important bioactive compounds that can contribute to chronic disease treatment and prevention. One area of the functional beverage market that has seen an increase in demand in recent years are beverages that promote relaxation and sleep. Sleep is an essential biological process, with optimal sleep being defined as one of adequate duration, quality and timing. It is regulated by a number of neurotransmitters which are, in turn, regulated by dietary intake of essential bioactive compounds. This narrative review aimed to evaluate the latest evidence of the sleep promoting properties of a selection of bioactive compounds (such as L-theanine and L-tryptophan) for the development of a functional beverage to improve sleep quality; and the effectiveness of traditional sleep promoting beverages (such as milk and chamomile). Overall, the bioactive compounds identified in this review, play essential roles in the synthesis and regulation of important neurotransmitters involved in the sleep-wake cycle. There is also significant potential for their inclusion in a number of functional beverages as the main ingredient on their own or in combination. Future studies should consider dosage; interactions with the beverage matrix, medications and other nutraceuticals; bioavailability during storage and following ingestion; as well as the sensory profile of the developed beverages, among others, when determining their effectiveness in a functional beverage to improve sleep quality.
... Rizon et al. believe that electroencephalography (EEG) is one of the most reliable physiological signals to detect the emotional state of the brain [7]. Kobayashi et al. conducted experiments on the influence of theanine on brain waves and found that theanine can be used as a new functional food ingredient in soothing foods and beverages [8]. It can be seen that tea has so many pharmacological effects and extensive effects that it cannot be replaced by other beverages. ...
Tea can help to regulate the mood of human. Based on the influence of tea on people's mood and attention, this study explored the tea concentration when the mood and attention of drinkers are in the best state, and established the best concentration model of tea. Using sampling experiment method to collect objective data, which are then combined with questionnaire survey method to collect subjective data, using the results to establish a neural network algorithm model to test the accuracy of the neural network algorithm model. Experiments show that the correlation coefficient of the output value of the BP neural network model constructed in this study is basically consistent with the actual prediction result. After obtaining data such as age, gender, frequency of tea drinking, and tea drinking concentration of tea drinkers, the constructed back propagation (BP) neural network model can accurately predict the mental state score of tea drinkers. The research will provide certain data support and theoretical basis for the follow-up development of the tea industry. Follow-up work needs to be performed in order to further adjust the scope and accuracy of the control model. Then, a more complete and accurate advanced BP neural network model can be established for different types of tea and other parameters.
... Theanine, chemical structure illustrated in Figure 1 (most of the tea theanine is the L-levorotary enantiomer), constitutes between 1 and 3% (on an average) of the total dry weight (dw) of tea leaves [7]. It has been known that theanine has multiple physiological effects on mammals such as: increases the Ȗ-aminoisobutyric acid (GABA) level [8], an amino acid derivative that functions as the chief inhibitory neurotransmitter in the mammalian central nervous system, creating a sense of relaxation approximately 40 min after oral ingestion [1]; stimulates the release of dopamine, a brain´s neurotransmitter responsible for confidence and sense of well-being [9]; stimulates production of alfa brain waves (an electromagnetic oscillations in the frequency range of 8-13 Hz), creating a state of deep relaxation and mental alertness [10]; and reduces hypertension and blood pressure [9]. In addition, theanine is thought to play a major role in preventing neuronal death that is a particularly important finding for the prevention of ischemia and strokes [11]. ...
... Studies that explored brain activity have previously reported that l-theanine intake increases a-wave activity. 29,30 A study by Gomez-Ramirez et al. 31 found that subjects who ingested 250 mg of l-theanine had increased a-wave activity for the attention task to be performed. Furthermore, a study that used a visuospatial task also showed that the intake of 250 mg of l-theanine contributed to sustained attention. ...
l-theanine (γ-glutamylethylamide), an amino acid in green tea, has been shown to affect brain functions by relieving stress disorders, improving mood, and maintaining normal sleep. However, the cognitive functions for which theanine is effective are unclear. This study aimed to clarify which cognitive functions are positively affected by intake of l-theanine. A double-blind, randomized, placebo-controlled study was conducted. The subjects were Japanese men and women aged 50-69 years. Mini Mental State Examination-Japanese version score was 24 or higher. Cognitrax was used as a test battery for cognitive function. Evaluations were performed before the intervention, after a single dose of l-theanine, and after 12 weeks of regular intake. The single dose of l-theanine reduced the reaction time to attention tasks (Stroop test, Part 1), and it increased the number of correct answers and decreased the number of omission errors in working memory tasks (4-Part continuous performance test, Part 4). In conclusion, our study indicated that l-theanine may contribute to improving attention, thus enhancing working memory and executive functions. Clinical Trial No.: UMIN000033812.
... Theanine (γ -glutamylethylamide). Theanine is the umami component of green tea, it has blood pressure-reducing effects in spontaneously hypertensive rats (Yokogoshi et al. 1995), and it can increase the feeling of relaxation in humans (Kobayashi et al. 1998). ...
The enzymatic characteristics of γ-glutamyltranspeptidase were elucidated. The catalytic nucleophile of the enzymatic reaction of Escherichia coli γ-glutamyltranspeptidase was identified as the Oγ of the N-terminal Thr-residue of the small subunit. It was demonstrated that the inactive precursor of γ-glutamyltranspeptidase is processed autocatalytically and intramolecularly into the active heterodimeric mature enzyme via an ester intermediate. The catalytic nucleophile of this processing reaction was identified as the same Oγ atom of the N-terminal Thr-residue of the small subunit. These results were also supported by the three-dimensional structures of the γ-glutamyl enzyme intermediate and of the precursor mimicked T391A non-processable mutant enzyme. Applications of transpeptidation and hydrolysis activities of bacterial γ-glutamyltranspeptidases were developed. Using transpeptidation activity, efficient enzymatic production of useful γ-glutamyl compounds, such as prodrug for Parkinson's disease, theanine and kokumi compound, was enabled. Hydrolysis activity was used as glutaminase and the mutant enzymes gaining glutaryl-7-aminocephalosporanic acid acylase activity were isolated.
... Theanine (γ-glutamylethylamide) is the major umami component of green tea 10 , a positive correlation between the grade of Japanese green tea and the concentration of theanine was reported 11 . It also decreases blood pressure of spontaneously hypertensive rats 12 and causes a feeling of relaxation 13 . The enzymatic method to synthesize Ltheanine from L-glutamine and ethylamine by GGT was developed 14 . ...
... Matcha is abundant in epigallocatechin gallate (EGCG), caffeine, and amino acids (especially theanine). Theanine is well known for reducing psychological and physiological stress responses evaluated by measuring salivary alpha-amylase and alpha-brain waves in human volunteers [3,4]. According to previous reports, it is required to take 200 mg of theanine at a time to obtain these effects. ...
Matcha has high contents of theanine, caffeine, and epigallocatechin gallate (EGCG). Among these, theanine reduces psychological and physiological stress responses, although this effect is disturbed by caffeine and EGCG. It was reported that the continued ingestion of high-quality matcha, whose molar ratio of caffeine and EGCG to theanine and arginine was kept at less than two, reduces stress responses. However, most matcha on the market has an inadequate ratio. Therefore, we investigated the influence of continued ingestion of matcha with a ratio of over two, on emotional behaviors after stress. Continued ingestion of matcha was suggested to reduce the anxiety-like behaviors induced by psychological and physiological stresses.
... L-Theanine (gglutamylethylamide), also found in tea plant is a unique amino acid that have gained focus in the field of neuroscience having significant neuroprotective effects (Kakuda, 2002a). Moreover, electroencephalographic (EEG) recordings in humans revealed that Ltheanine consumption during resting state increased the activity of alpha frequency band (8-14 Hz) (Kobayashi, 1998;Juneja, 1999). In a dose dependent manner, L-theanine crosses the blood-brain barrier within 30 minutes of ingestion and thought to influence the release of neurotransmitters. ...
Non-alcoholic beverages comprise of Caffeine and L-theanine as core ingredients. Caffeine is attributed to augment cardiovascular and neurophysiological responses by enhancing the neurotransmission of catecholamines after binding with adenosine receptors antagonistically. L-theanine, as a constituent of green tea is helpful in lowering blood pressure by antagonizing the effects of excitatory neurotransmitters after subsequent release of inhibitory neurotransmitter GABA. 87 healthy females with age 18-19 years, participated in the study were divided into three different groups. Group A was subjected to consume cold beverage (soft drink). Participants of group B & C were allowed to take hot beverages in the form of tea and green tea respectively. Cardiovascular parameters and neurophysiological responses were assessed before and after 45 minutes of beverages intake.Statistical analysis revealed a significant improvement in the reaction time of tea and in concentration test of both tea and green tea consumers. In addition, a less significant increase in HR with tremendous decrease in PR was observed among green tea consumers. Furthermore, significant reduction in both systolic & diastolic blood pressure was evident with green tea consumers.Experimental results are unveiling effectiveness of L-theanine over caffeine in lowering BP, HR & PR after antagonizing the release of excitatory neurotransmitter along with the opening of ligand gated chloride channels that leads to hyperpolarization. Moreover, a favorable combination of caffeine & L-theanine is responsible for enhancing cognitive performances, alertness and well being
... While green tea intake also increased dopamine levels in all the treated groups. These increase could be due to 2% of the dry een tea, because drinking two to four cups of green tea every day is equivalent to -theanine [49]. theanine is able to exert its effect on dopamine because of its ability to cross the blood-brain mine levels in the brain has also been shown to exert neuroprotective effects in animal models possibly through its antagonistic effects on group 1metabotrophic glutamate receptors [51]. ...
Aim: This study investigated the impact of MPTP induced Parkinson’s disease (PD) and the protective and/or curative effects of green tea on the retina. Study Design: Twenty-five adult male mice (Mus musculus) weighing between 20-30 grams were used for this study. The mice were randomly placed into five groups of five mice each: A (Control; mice pellets), B (1Methyl -4-phenyl-2, 3, 6-tetrahydropyridine (MPTP) 10 mg/kg, IP), C (MPTP + Green tea (GT); 300 mg/kg GT orally), D (GT + MPTP), E (GT; 300 mg/kg). Methodology: At the end of the experimental protocols, the eyes were excised weighed and processed to determine the neurotransmitter [Dopamine, Gamma amino butyric acid (GABA) and calcium ion (CA²⁺)] levels in the retina spectrophotometrically and histology of the retina using Hematoxylin and Eosin (H&E) stain. Results: The results showed significant (P<0.005) reduction in the relative eye to body weight and increase in the retinal diameter in the MPTP group when compared with the control. Whereas treatments with green tea did not significantly (P<0.005) increase the relative eye to body weight but intake of green tea alone does, while the retinal diameter is significantly reduced by pretreatment with green tea. The concentration of Calcium was significantly increased by MPTP and significantly reduced by green tea intake, whereas only the green tea alone and green tea cotreated groups significantly increased dopamine levels. Conclusion: From our results we can preliminary conclude that green tea conferred protection on the retina against the adverse effects of MPTP in mice model of Parkinson’s disease.
... It has been reported that oral administration of 50-200 mg of L-theanine in humans induces alpha-brain wave activity, which correlates with relaxation. (39,40) Taken together with these findings, our results suggest that L-theanine could be a useful and safe compound and it exerts neuroprotective effects against DA quinone-induced neuronal damage by released humoral molecules, in part, by glutathione from astrocytes. ...
l-Theanine (γ-glutamylethylamide), a component of green tea, is considered to have regulatory and neuroprotective roles in the brain. The present study was designed to determine the effect of l-theanine on excess dopamine-induced neurotoxicity in both cell culture and animal experiments. The primary cultured mesencephalic neurons or co-cultures of mesencephalic neurons and striatal astrocytes were pretreated with l-theanine for 72 h, and then treated with excess dopamine for further 24 h. The cell viability of dopamine neurons and levels of glutathione were evaluated. Excess dopamine-induced neurotoxicity was significantly attenuated by 72 h preincubation with l-theanine in neuron-astrocyte co-cultures but not in neuron-rich cultures. Exposure to l-theanine increased the levels of glutathione in both astrocytes and glial conditioned medium. The glial conditioned medium from l-theanine-pretreated striatal astrocytes attenuated dopamine-induced neurotoxicity and quinoprotein formation in mesencephalic neurons. In addition, replacement of l-glutamate with l-theanine in an in vitro cell-free glutathione-synthesis system produced glutathione-like thiol compounds. Furthermore, l-theanine administration (4 mg/kg, p.o.) for 14 days significantly increased glutathione levels in the striatum of mice. The results suggest that l-theanine provides neuroprotection against oxidative stress-induced neuronal damage by humoral molecules released from astrocytes, probably including glutathione.
... [4] L-theanine facilitates the generation of alpha waves in the brain, which are believed to be associated with a relaxed yet alert mental state. [5] This effect has been confirmed in clinical studies as well. [6] Though there are only a few human data on the interaction of these two compounds, it is obvious that the ratio of theanine and caffeine determines the degree of stimulant effect of tea drinks. ...
Background:
Caffeine and L-theanine are pharmacologically important constituents of tea, especially due to their effects on the central nervous system. The effects of these two compounds are opposite: While caffeine is a well-known stimulant, theanine has a relaxing effect. Tea processing may influence the caffeine and theanine content of tea leaves.
Objective:
The aim of our work was to quantify these constituents from a set of commercial products to reveal the possible correlations of caffeine and theanine content and processing methods.
Materials and methods:
Theanine and caffeine contents of 37 commercial white, green, oolong, black, and pu-erh tea samples were quantified by high-performance liquid chromatography-diode array detector.
Results:
The mean L-theanine content of white, green, oolong, and black teas were 6.26, 6.56, 6.09, and 5.13 mg/g, respectively. The same values for caffeine content were 16.79, 16.28, 19.31, and 17.73 mg/g.
Conclusion:
Though the effect of processing on theanine content was evident, quantification for these analytes does not seem to be a good criterion to discriminate the different types of tea. Caffeine content provided no information on the effect of processing, and the theanine content of the samples was rather variable, independently from the type of the tea. The quantitative analysis of caffeine and theanine is essential to assess the stimulating effect of the tea, however, for chemical profiling further secondary metabolites have to be determined.
Summary:
Thirty-seven commercial white, green, oolong, black, and pu-erh tea samples were analyzed for caffeine and theanine contentWhile the caffeine content was similar, the theanine contents of black teas were slightly lower and practically zero in pu-erhThe great variability of these two compound within the tea categories allows no discrimination of tea types based solely on theanine and caffeine quantificationContrary to the previous data, the way of processing has no determining effect on theanine content. FigureAbbreviations used: CZE: Capillary zone electrophoresis, DAD: Diode array detector, EEG: Electroencephalography, GC: Gas chromatography, HPLC: High-performance liquid chromatography, IR: Infrared spectroscopy, MEKC: Micellar electrokinetic capillary chromatography, MS: Mass spectrometry, RP: Reversed phase, RSD: Relative standard deviation, SD: Standard deviation, TLC: Tile liquid chromatography, UV: Ultraviolet.
... It has been reported that after administration to rats, EGCG "significantly reduced food intake, body weight, blood levels of testosterone, estradiol, leptin, insulin, insulin-like growth factor I, glucose, cholesterol and triglyceride" (Kao et al, 2000). L-Theanine, a neurologically active non protein amino acid, originally derived from the leaves of the tea plant quells anxiety and stress without negative side effects (Juneja et al, 1999) and promotes a sense of relaxation and well being without causing drowsiness (Kobayashi, 1998;Song, 2003). ...
Effect of chronic treatment of standardized hot water extract of Camellia sinensis (BTE) for 14 days on stress and hypertensive models of rat, behavioural (learning and memory) testing (Shuttle box avoidance test), brain EEG activity and serum neurotransmitter (NE, 5-HT, DA) was studied in male Charles Foster strain rats. The result revealed that oral pretreatment with BTE (5ml/kg) markedly increase in the performance of active avoidance learning in the Shuttle box avoidance test. Electroencephalographic recording showed that BTE pretreatment to experimental animals elicited significant decrease in β-waves and increase in α-waves. It also resulted in the elevation of serum serotonin (5-HT) level and significant decrease in norepinephrine (NE) level. The present study suggests that chronic administration of BTE helps in combating stress and hypertension possibly by altering serum monoamine level.
... a wave of the brain is especially thought to be the indicator of relaxation (Juneja et al., 1999). It is stated that, 40 minutes after orally taking L-theanine (50-200 mg) a waves occur on the occipital and parietal areas of the brain and that causes relaxation without causing a state of sleep (Kobayashi et al., 1998). Song et al. (2003) found out that 200 mg L-theanine increased the alpha (a) activity in the frontal and occipital areas 40 minutes after it was taken by individuals with high anxiety levels (Song et al., 2003). ...
Tea has been a very popular beverage around the world for centuries. The reason that it is delicious, enabling hydration, showing warming and relaxing effect can be mentioned why it is consumed so much in addition to its prominent health effects. Although the catechins and caffeine are the primary bioactive components that are related with the health effects of the tea, the health effects of theanine amino acid, which is a non-proteinic amino acid special to tea, has become prominent in recent years. It has been known that the theanine amino acid in tea has positive effects especially on relaxing, cognitive performance, emotional status, sleep quality, cancer, cardiovascular diseases, obesity and common cold. The results of acute and chronic toxicity tests conducted on the safety of theanine express that L-theanine is reliable in general even if it is consumed too much with diet. However, it is not revealed a clear evidence based result yet regarding theanine metabolism, health effects and its safety. Within this frame, chemical structure of theanine, its bio-synthesis, dietary sources, metabolism, health effects, and safety are discussed in present study.
... L-theanine has a documented EEG alpha enhancement effect in the research literature (Juneja et al., 1999;Kimura et al., 2007;Kobayashi et al., 1998). While we did not find such an effect with our higher cacao-content + L-theanine confection, we theorize this to be due to the sympathomimetic ingredients in chocolate suppressing slow wave (alpha and theta) and enhancing fast wave (beta) activity. ...
Objective: The present study investigated the effects of consuming chocolate on electroencephalograph (EEG) frequencies and localization and on blood pressure. Method: Across six conditions, 122 participants consumed either higher (60%) cacao chocolate, low (0%) cacao chocolate, higher cacao chocolate + L-theanine, high sugar water, low sugar water, or water. EEGs, blood pressure, and mood were measured before and after a 60-min digestion period. Results: Analyses indicated a decrease in frontal, parietal, and temporal theta and an increase in occipital beta EEG following the consumption of a 60% cacao confection compared with control conditions. Diastolic blood pressure increased with the consumption of higher cacao chocolate when compared to water alone and to higher cacao chocolate + L-theanine. Diastolic and systolic blood pressure decreased following consumption of higher cacao + L-theanine chocolate, averaging 4–8 mmHg. No condition-specific mood changes or gender differences were found. Conclusions: This study suggests an acute stimulating effect of cacao on the human brain and vasoconstrictive effects on peripheral vasculature, the latter of which appear to be offset by an L-theanine additive. Significance: This is the first known study to investigate acute EEG effects of consuming chocolate and suggests a potential attention-enhancing effect.
... Various reports indicate that tea extracts have biological and pharmacological activities such as antioxidant, [10] antiviral, [11] antibacterial, [12] anticarcinogenic, [13,14] antimutagenic, [15] anti-inflammatory, [16] anti-aging, [17] anti-diabetic, [18,19] body weight control, [20,21] reducing stress and anxiety, improving learning and concentration [22,23] and anti-HIV effect. [24,25] Leishmaniasis is a vector born disease caused by protozoan parasites of the genus Leishmania.(L) ...
In this study four tea samples Gumero black, Wushwush black and Wushwush green from Agri- Ceft Plc and East Africa black tea leaves from East African Agribusiness Plc were investigated for total polyphenols, caffeine, catechin and L-theanine content.
The aqueous extracts were investigated for their antioxidant and antileishmanial property and effect on amphotericin B, miltefocine and sodium stibogluconate, the commonly used antileishmanial drugs. Antileishmanial studies were conducted on L. aethiopica.
Wushwush green tea had the highest content of polyphenol (19.98 ± 1.15 mg gallic acid equivalent /100 g dry leaf weight), catechin (37.06 mg/g) and L-theanine (48.54 mg/g but the lowest caffeine content). It exhibited the highest antioxidant activity. The highest antioxidant effect of Wushwush green tea may be attributed to the highest polyphenol content. East African black tea had the lowest L-theanine (20.72 mg/g) and antioxidant activity but the highest caffeine (16.60 mg/g) content.
Wushwush green tea showed slight inhibitory effect on L. aethiopica while the lack tea extracts (Gumero, East Africa and Wushwush) exhibited no antileishmanial activity. Wushwush green tea did not show any synergistic or antagonistic effect on the antileishmanial drugs used in this study while Gumero, East Africa and Wushwush black tea extracts exhibited dose dependant inhibitory activity to the commonly used antileishmanial drugs included in this study.
... Moreover, it was clarified that the thermogenesis by caffeine was synergistically enhanced with catechins in rat adipose tissues [75]. Theanine (Áglutamylethylamide) is a main amino acid peculiar to green tea and has physiological effects such as relaxation activity [76], activation of dopamine metabolism, and release in the brain [77]. Moreover, it was reported that theanine suppressed excitation by caffeine [78]. ...
Obesity is a global health problem affecting all age groups, leading to many complications such as type 2 diabetes, systemic hypertension, cardiovascular disease, dyslipidemia, atherosclerosis, and stroke. Physiologically, obesity arises from metabolic changes in the tissues and organs of the human body; these changes result in an imbalance between energy intake and energy expenditure, which in turn results in increased fat accumulation in adipose tissue. Such fat accumulation predisposes individuals to development of several health problems. Two different obesity treatment drugs are currently on the market; Orlistat, which reduces intestinal fat absorption via inhibiting pancreatic lipase, and Sibutramine, an anorectic or appetite suppressant. Both drugs have hazardous side effects, including increased blood pressure, dry mouth, constipation, headache, and insomnia. For this reason, a wide variety of natural materials have been explored for their obesity treatment potential. Therefore, the present review focuses on the safety and efficacy of some herbal medicines in the management of obesity through covering their beneficial effects and mechanism of action.
Overview
A novel highly bioavailable curcumin-galactomannan (CGM) formulation was shown to have improved blood-brain-barrier (BBB) permeability of free curcuminoids in animal models; however, this has not been established in humans. The present study was conducted to determine the functional effects of CGM on brain waves in healthy individuals, owing to its BBB permeability.
Methods
A total of 18 healthy volunteers aged 35–65 were randomly assigned to consume 500 mg CGM, Unformulated curcumin (UC) or Placebo capsules twice daily for 30 days. Electroencephalogram (EEG) measurements, audio-visual reaction time tests and a working memory test were conducted at baseline and after 30 days.
Results
Supplementation of CGM resulted in a significant increase in α- and β-waves (p < 0.05) as well as a significant reduction in α/β ratio in comparison with unformulated curcumin and placebo groups. Furthermore, the CGM showed significant reduction in the audio-reaction time (29.8 %; p < 0.05) in comparison with placebo and 24.6% (p < 0.05) with unformulated curcumin. The choice-based visual-reaction time was also significantly decreased (36%) in CGM as compared to unformulated curcumin and placebo which produced 15.36% and 5.2% respectively.
Conclusion
The observed increase in α and β waves and reduction in α/β ratio in the CGM group suggest that CGM can influence the brain waves in healthy subjects in a manner consistent with penetration of the blood-brain-barrier. The EEG results correlated with improved audio-visual and working memory tests which further support the role of CGM on memory improvements and fatigue reduction.
γ-Glutamyltranspeptidase (GGT) has been widely used as a marker enzyme of hepatic and biliary diseases and relations between various diseases and its activity have been studied extensively. Nevertheless, several of its fundamental enzymatic characteristics had not been elucidated. We obtained homogeneous preparation of GGTs from bacteria, characterized them, and elucidated its physiological function that is common to mammalian cells, using GGT-deficient E. coli. Prior to GGT of all living organisms, we also identified catalytic nucleophile of E. coli GGT and revealed the post-translational processing mechanism for its maturation, and also its crystal structure was determined. The reaction intermediate was trapped and the structure-based reaction mechanism was presented. As for its application, using its transferase activity, we developed the enzymatic synthesis of various γ-glutamyl compounds that are promising in food, nutraceutical and medicinal industries. We found GGT of Bacillus subtilis is salt-tolerant and can be used as a glutaminase, which is important in food industry, to enhance umami of food, such as soy sauce and miso. We succeeded in converting bacterial GGT to glutaryl-7-aminocephalosporanic acid acylase, which is an important enzyme in cephem antibiotics production, by site-directed and random mutagenesis.
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.
Green tea from Camellia sinensis L. has different tastes and physiological functions according to the temperature of water used when brewing the tea leaves. Green tea brewed with boiled water (especially "Sencha") has a strong astringent taste as epigallocatechin gallate (EGCG) and caffeine are extracted with hot or boiled water. These compounds elicit strong astringency and bitterness, and were previously considered the principal functional ingredients in green tea. In contrast, cold-water brewed "Sencha" has much less bitterness and astringency than hot-water brewed "Sencha" because EGCG and caffeine are difficult to extract in cold water. Therefore, the tastes of amino acids predominate in cold-water brewed "Sencha" because they are easily extracted in cold water. The main functional components of cold-water brewed "Sencha" are epigallocatechin (EGC) and theanine, which are easily extracted in cold water. The functions of EGC have not attracted much attention thus far. However, it was recently found that EGC has an immune-enhancing effect and theanine has a psychosocial stress-reducing effect. These effects of EGC and theanine were inhibited by EGCG and caffeine; therefore, to obtain these effects, green tea needs to be brewed with cold water.
This paper describes a simple analytical method for the determination of L-theanine, a major free amino acid in green tea, by high-performance liquid chromatography (HPLC) with ultraviolet detection (UV). This method provides high linearity of the working curve for calibration as well as repeatability. The correlation coefficient of the working curve for calibration was estimated to be to 0.9991 for L-theanine in the concentration range from 1 mg L−1 to 100 mg L−1. The limit of detection (LOD) was calculated on 3σ at 1 mg L−1 as 0.210 mg L−1 using a standard solution for L-theanine. The limit of quantification (LOQ) was calculated on 10σ at 1 mg L−1 as 0.704 mg L−1 using a standard solution for L-theanine. In addition, the recoveries of spiked the bottled green-tea drinks at concentration levels from 10 to 75 mg L−1 were estimated to be 91.1–99.3%, and the relative standard deviations were 1.04–2.51%. This method could be successfully applied to the determination of the L-theanine in bottled green-tea drinks.
In this work the role of γ-glutamyl transpeptidase in the metabolism of γ-glutamyl dipeptides produced by C. glutamicum ATCC 13032 was studied. The enzyme is encoded by the gene ggtB (cg1090) and synthesized as a 657 amino acids long preprotein. Gamma-glutamyl transpeptidase activity was found to be associated with intact cells of C. glutamicum and was abolished upon deletion of ggtB. Bioinformatic analysis indicated that the enzyme is a lipoprotein and is attached to the outer side of the cytoplasmic membrane. Biochemical parameters of recombinant GgtB were determined using the chromogenic substrate γ-glutamyl-p-nitroanilide. Highest activity of the enzyme was measured in sodium bicarbonate buffer at pH 9.6 and 45°C. The KM value was 123μM. GgtB catalyzed the concentration-dependent synthesis and hydrolysis of γ-glutamyl dipeptides and showed strong glutaminase activity. The intracellular concentrations of five γ-glutamyl dipeptides (γ-Glu-Glu, γ-Glu-Gln, γ-Glu-Val, γ-Glu-Leu, γ-Glu-Met) were determined by HPLC-MS and ranged from 0.15 to 0.4mg/g CDW after exponential growth in minimal media. Although deletion and overexpression of ggtB had significant effects on intracellular dipeptide concentrations, it was neither essential for biosynthesis nor catabolism of these dipeptides in vivo.
Methylmercury (MeHg) is an environmental toxicant that leads to long-lasting neurological and developmental deficits in animals and humans. L-Theanine is a relatively uncommon amino acid found almost exclusively in green tea leaves. This study was aimed to evaluate the effect of L-Theanine (LT) on MeHg induced oxidative stress in cerebellum of rats. Male Wistar rats were administered with MeHg orally at a dose of 5 mg/kg b.w. for 21 days. Experimental rats were given MeHg and also administered with LT (100 mg/kg, orally) 1 hour prior to the administration of MeHg for 21 days. After treatment period, MeHg exposure significantly decreased the level of glutathione and the activities of superoxide dismutase, catalase and, glutathione peroxidase. Whereas, the thiobarbituric acid reactive substances and the activity of glutathione reductase were found to be increased. Behavioural changes like decreased motor coordination, increased immobility, decreased tail flick responses and decreased locomotor activities were also observed along with Histopathological alterations. All the above behavioural, biochemical and histopathological changes were found to be reversed by pretreatment with LT. © 2015, International Journal of Pharmacognosy and Phytochemical Research. All rights reserved.
To utilize the functional ingredients of tea leaves, we examined conditions for rapidly extracting O-methylated catechins, epigallocatechin (EGC) and theanine using a tea infuser, "Rich plus (RICH(R))". Nineteen mg of O-methylated catechins per cup (120 mL) could be extracted with water at 94 degrees C in 20 seconds with stirring using 1.9 g of "Benifuuki" green tea that contained 1.7% of O-methylated catechins by weight. Thirty-nine mg of EGC and an EGC/EGCG ratio of 2.5 could be extracted at 10 degrees C in 30 seconds with stirring using 1.5 g of 'Yutakamidori' green tea in which the EGC/EGCG ratio was about one. Twenty mg of theanine could be extracted at 65 degrees C in 20 seconds with stirring using 1.7 g of 'Saemidori' green tea that contained 1.4% by weight theanine. These quantities correspond to approximately half the daily recommended intake of O-methylated catechins and EGC that the anti-allergic action and immunostimulating action have been described in the manuscripts.
Objectives:
Tea has been associated with many mental benefits, such as attention enhancement, clarity of mind, and relaxation. These psychosomatic states can be measured in terms of brain activity using an electroencephalogram (EEG). Brain activity can be assessed either during a state of passive activity or when performing attention tasks and it can provide useful information about the brain's state. This study investigated the effects of green and black consumption on brain activity as measured by a simplified EEG, during passive activity.
Methods:
Eight healthy volunteers participated in the study. The EEG measurements were performed using a two channel EEG brain mapping instrument - HeadCoach™. Fast Fourier transform algorithm and EEGLAB toolbox using the Matlab software were used for data processing and analysis.
Results:
Alpha, theta, and beta wave activities were all found to increase after 1 hour of green and black tea consumption, albeit, with very considerable inter-individual variations.
Discussion:
Our findings provide further evidence for the putative beneficial effects of tea. The highly significant increase in theta waves (P < 0.004) between 30 minutes and 1 hour post-consumption of green tea may be an indication of its putative role in cognitive function, specifically alertness and attention. There were considerable inter-individual variations in response to the two teas which may be due genetic polymorphisms in metabolism and/or influence of variety/blend, dose and content of the selected products whose chemistry and therefore efficacy will have been influenced by 'from field to shelf practices'.
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