No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
How much theanine in a cup of tea? Effects of tea type and method of preparation
Abstract
Recent interest into the possible benefits of l-theanine found in tea has raised the issue that there are few data available on amounts of l-theanine contained in cups of commercially-available teas, prepared by a standard method. HPLC along with a standard method of preparing tea was employed here to determine amounts of l-theanine in cups of tea and the effects that various preparation factors have on amounts of l-theanine extracted. Brewing time was found to be a major determinant of the amount of l-theanine extracted, while the addition of small amounts of milk and sugar made no significant difference. High levels of milk resulted in a marked lowering of the level of detectable l-theanine. Contrary to previous research, a standard (200ml) cup of black tea was found to contain the most l-theanine (24.2±5.7mg) while a cup of green tea contained the least (7.9±3.8mg).
... Our findings of 163.2 mg/100 g of theanine in a cup of regular oolong tea are in keeping with these previous studies. One study that prepared tea for analysis similar to the method used in the present investigation (brewing for a specified period of time in 200 mL water) found a standard (200 mL) cup of black tea contained 24.2 mg L-theanine, white tea contained 11.5 mg, while a cup of green tea contained the least theanine at 7.9 mg [27]. These values are lower than those that we report and may be related to the type of tea tested. ...
... These values are lower than those that we report and may be related to the type of tea tested. Oolong tea was not investigated by Keenan and colleagues [27]. ...
... On the other hand, Wang et al., [8] and Tsushida and Murai [7] found that GABA enrichment did not substantially alter theanine concentration compared to non-enriched teas. Moreover, theanine content in black teas was shown to be equivalent to green and oolong teas [25][26][27], therefore it appears to remain unaffected by oxidation. ...
We have previously shown that the consumption of GABA-enriched oolong tea is effective in reducing stress in a student cohort. However, key constituent content has not been previously investigated, especially as applied to a standard cup of tea. Further, it has not been substantiated whether it is the suggested GABA content or other constituents that lead to these observed changes in stress behaviour. Using reverse-phase HPLC, we determined the actual content of four chemicals known to influence stress in 200 mL cups of regular or GABA-enriched oolong tea brewed to manufacturer’s instructions. We found eight times as much γ-aminobutyric acid (GABA) and 1.5 times as much caffeine in GABA-enriched oolong tea as in regular oolong tea. In contrast, there was 10 times less epigallocatechin gallate (EGCG), and half as much theanine in the GABA-enriched tea. Thus, there are changes in multiple constituents in GABA-enriched oolong tea that may contribute to the biological effects we observed in students consuming these teas.
... FDA suggests that the daily consumption amount of L-theanine should not exceed 1200 mg (Vuong et al., 2011;FDA, 2006). A standard cup of around 200 ml of black tea contained 24.2 mg and 7.9 mg in green tea (Keenan et al. 2011). This review insights on the nutritional significance of L-theanine with the impact of processing on it, and also the benefits and extraction method are review. ...
... • How long the tea or tea bag is left to infuse • Whether the tea bag is dunked or stirred and left or removed (Keenan et al. 2011) Tea powder, in combination with sugar and milk used for the preparation of tea beverages. As per the Tea Appreciation Society, 98% of people take milk in their tea. ...
... According to a study, it was proved that the amount of L-theanine present in black tea samples was significantly higher than green and white tea varieties (Keenan et al. 2011). It was proved that milk and sugar do not affect the amount of L-theanine extracted (Keenan et al. 2011). ...
Tea is the second most consumed beverage around the world after water. Apart from other tea preparations, approximately 98% of peoples drink tea with milk. The essential bioactive component, i.e., L-theanine present in tea along with catechins, tannin, and polyphenols, which has prominent health benefits, including relaxation. L-theanine is proteionic amino acid present only in tea, and which is safe for daily intake. This review focused on L-theanine present in different types of tea, commercially available tea powders, extraction methods for L-theanine isolation, characterization, and health benefits of L-theanine.
... The extent of fermentation has been found to be determinant of the concentration of L-theanine, with more theanine contained in unfermented teas and less in fermented teas. [10] If steaming is avoided during the processing of green tea, the final product is remarkably rich in theanine (>2% theanine). [11] Nevertheless, other factors also influence the composition of the final product, since some green teas are almost devoid of theanine, and there are black teas with remarkable theanine content. ...
... [11] Nevertheless, other factors also influence the composition of the final product, since some green teas are almost devoid of theanine, and there are black teas with remarkable theanine content. [10] However, the presence of caffeine in the tea counteracts the relaxing effect. The amount of caffeine in different tea varieties is unaffected by the various processing methods. ...
... [12] Apart from the composition of the raw material, the way the tea is prepared by the consumer (grade of comminution of tea leaves, extraction time, temperature, drug extract ratio, stirring, and addition of milk) has also major influence on the concentration of theanine and caffeine in the tea drink. [10] Despite the practical relevance of the quantity of caffeine and theanine in tea leaves, there are only a few papers dealing with the simultaneous quantification of these substances from tea drinks or dry tea leaves. In case of caffeine, a plethora of methods, including gravimetric, spectrophotometric, gas chromatographic (GC), high performance liquid chromatography coupled with UV detection (HPLC-UV), HPLC-mass spectrometry (HPLC-MS), chemometric, infrared spectroscopic (IR), capillary electrophoretic and electroanalytical protocols are available for quantification. ...
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.
... These characteristics make the identification of healthy foods containing natural free amino acids an interesting research topic. In particular, theanine, a natural free amino acid, is mainly found in plant and fungal species, providing a unique savory flavor to green tea infusions [4]. The United States Food and Drug Administration (FDA) determined theanine to be a safe dietary supplement. ...
... In the tea industry, visible identification and quantification of natural free amino acid, e.g., theanine, is necessary for determining high-quality products due to its unique flavor and potential health benefits. Based on the literature [4], we recognized that theanine could exist in a maximum amount of 0.57 mM and 0.23 mM in black tea infusion and green tea infusion, respectively. Our detection method is available to detect theanine down to 0.826 mM, and therefore should have improved sensitivity for its applications. ...
Natural free amino acids present in plant extracts or tea infusions provide a unique flavor and potential effect on anxiety and blood pressure reduction. Accordingly, quantifying free amino acids in foods has been of interest to food science and analytical research fields. The ninhydrin solution-based assay is a colorimetric method based on the formation and detection of Ruhemann’s purple complex. Media-based colorimetric detection requires specialized facilities and personnel; moreover, it can suffer from the interference of the analyte color. In this study, we developed ninhydrin-loaded microcapsules and a simple free amino acids detection procedure, by simply dipping the microcapsules into the analyte solution for 3 min. Among the five tested natural free amino acids, theanine exhibited the highest colorimetric response to microcapsule-based detection, with a limit of detection of 0.826 mM.
... An early trial in 75 healthy men found that 6 weeks' tea consumption reduced cortisol levels in response to a stressful task compared to placebo with a relative increase in subjective relaxation during the post-task recovery period [10]. L-theanine, an amino found in both black and green tea and to a greater extent in black than green tea (24.2 ± 5.5 mg vs 7.9 ± 3.8 mg) [11] may, alongside caffeine, be responsible for the mood responses to tea. It needs to be noted here that this study did not include matcha, a powdered green tea that is known to have higher L-theanine contents than standard green teas [12]. ...
... Tea consumption has been found to improve mood and reduce physiological stress response with a reduction in blood cortisol levels [11][12][13]. Whilst caffeine has been thought to be the main contributor to the mood improvement effects of tea, our findings indicate that L-theanine, an amino acid present in black tea and green tea, with recent evidence showing that it is found in black tea in greater concentrations, may be a key bioactive responsible for mood and mental health improvement. This review also shows the potential benefits of L-theanine on memory and alertness with an ability to act in concert with caffeine but to dampen the stimulant spike of caffeine and induce relaxation [15]. ...
Tea (Camellia sinensis) is the most commonly consumed beverage globally after water, with black tea being the most popular type of tea drunk in Britain by people of all ages. The potential for tea to contribute to health and wellness throughout life is worthy of consideration. Tea is a low calorie drink with several bioactive polyphenol ingredients which are well known to have antioxidant activity. Black tea in particular is a source of the amino acid L-theanine which has been linked with benefits for mental, immune and cardiovascular health. Prevalence of poor health, including poor cardiovascular, metabolic, mental, brain, bone and immune health, which may result in serious outcomes, including heart disease, type 2 diabetes, osteoporosis, cognitive decline and an inability to fight infection, is high in the UK and the European region. Interest in safe, natural ingredients for promoting health and wellness is growing. Whilst tea has been consumed for centuries, its health benefits have emerged more powerfully during recent decades giving scientific credence to the traditional perception that tea makes those who include it in their pattern of daily life feel good. This review collates evidence from human studies which evaluate the health and wellness impacts of tea consumption throughout life including into old age. It explores the evidence available on tea and mental and cognitive health, cardiovascular health, metabolic health, bone health, gut health and immune health. It identifies the bioactive ingredients which are likely contributors to these health impacts and includes evidence from laboratory studies that help to explain the mechanisms by which these benefits may occur. Overall, this review concludes that tea consumption contributes to health and wellness throughout life and that everyone should be encouraged to enjoy three cups daily as part of a healthy lifestyle pattern.
... In another study, it was found out that, green tea had lower levels of L-theanine when compared to oolong tea and black tea (Ekborg-Ott et al., 1997). In another study, it was found out that 200 mL of black tea had higher levels of L-theanine (respectively: 24.2 § 5.7, 7.9 § 3.8 mg) compared to green tea (Keenan et al., 2011). In another study the brewing time of tea is the most important determining aspect of tea in terms of L-theanine concentration and the milk and sugar added in small quantities do not cause important differences in the concentration (Keenan et al., 2011). ...
... In another study, it was found out that 200 mL of black tea had higher levels of L-theanine (respectively: 24.2 § 5.7, 7.9 § 3.8 mg) compared to green tea (Keenan et al., 2011). In another study the brewing time of tea is the most important determining aspect of tea in terms of L-theanine concentration and the milk and sugar added in small quantities do not cause important differences in the concentration (Keenan et al., 2011). In another study, it was found out that a standard mug of 200 mL had 10-20 mg/L (Hilal and Engelhardt, 2007). ...
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.
... Therefore, the elimination of matrix effects is vital. PFT naturally contains pigments, polyphenols, catechins, L-theanine, proteins, lipids, and other active ingredients [51]. These constituents affect the accuracy of the mycotoxin determinations [52]. ...
Post-fermented tea (PFT) is one of the most commonly consumed beverages worldwide. Rapid microbial growth and significant changes in the microbial composition of PFT during processing and storage pose a potential risk of contamination with mycotoxins such as zearalenone (ZEN). Screening for ZEN contamination in a simple, rapid, and inexpensive manner is required to ensure that PFT is safe for consumption. To monitor ZEN in PFT, ZEN was conjugated with bovine serum albumin to prepare egg yolk immunoglobulins (IgY). A specific indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) based on IgY was developed and validated. ZEN was extracted with acetonitrile and water (50:50, v/v) containing 5% acetic acid and purified using a mixture of primary and secondary amines and graphitized carbon black to remove matrix interference from the PFT samples. Under optimal conditions, the linear range of this assay was 13.8−508.9 ng mL−1, the limit of detection was 9.3 ng mL−1, and the half-maximal inhibitory concentration was 83.8 ng mL−1. Cross-reactivity was negligible, and the assay was specific for ZEN-related molecules. The recovery rate of ZEN in the control blanks of PFT samples spiked with a defined concentration of ZEN of 89.5% to 98.0%. The recovery and accuracy of the method were qualified for PFT matrices. No significant differences were evident between the results of the actual PFT samples analyzed by high-performance liquid chromatography and ic-ELISA. The collective data indicate that the developed ic-ELISA can be used for the rapid and simple detection of ZEN in PFT products.
... Kazan, Seddik, Marstani, Elsutohy, and Yasri (2019) documented that the level of Glu and Trp in green tea and Gly in oolong tea was higher in comparison to other amino acids. About 25 mg of L-theanine is present in black tea (200 mL cup), 7.9 mg in a cup of green tea, and 0.2-2.4% (w/w) in green tea leaves of commongrade (Keenan, Finnie, Jones, Rogers, & Priestley, 2011). Fermentation influences the amino acid profile as well as decreases the total FAAs. ...
Tea residues represent one of the major agricultural wastes that are generated after the processing of tea. They account for 21–28% of crude protein and are often discarded without the extraction of valuable proteins. Due to various bioactivity and functional properties, tea proteins are an excellent alternative to other plant-based proteins for usage as food supplements at a higher dosage. Moreover, their good gelation capacity is ideal for the manufacturing of dairy products, jellies, condensation protein, gelatin gel, bread, etc. The current study is the first to comprehend various tea protein extraction methods and their amino acid profile. The preparation of tea protein bioactive peptides and hydrolysates are summarized. Several functional properties (solubility, foaming capacity, emulsification, water/oil absorption capacity) and bioactivities (antioxidant, antihypertensive, antidiabetic) of tea proteins are emphasized.
... L-theanine is structurally similar to glutamic acid which is the precursor of the excitatory neurotransmitter glutamate. The content of L-theanine in a cup of tea ranges from 4 to 22 mg, depending on the type of tea and the brewing time [1][2][3]. Purified L-theanine is used as a nutritional supplement and a food additive [4,5]. ...
Background:
L-theanine is a non-protein-forming amino acid found in tea. Previous research shows high doses (100-400 mg) of L-theanine enhances attention, mainly by reducing mind wandering and distracter processing. We hypothesized that these indirect mechanisms could significantly improve the performance of low-level attentional tasks, whereas the relative contribution could be less in complex attentional tasks that require active, higher-order processing of target stimuli.
Methods:
To test this hypothesis, we conducted a double-blind, placebo-controlled, counterbalanced, four-way crossover study in 32 healthy young adults, where we compared the effects of three doses of L-theanine (100, 200 and 400 mg) with a placebo (distilled water), administered before and 50 min after dosing, on three attentional tasks from the Cambridge Neuropsychological Test Automated Battery [viz. Reaction Time (RTI)-visuomotor speed, Rapid Visual Information Processing (RVP)-sustained attention, and Stop Signal Task (SST)-inhibitory control]. Results were analyzed in dose × time repeated measures ANOVA models, with subsequent pairwise comparisons.
Results:
Active doses significantly improved reaction times in the RTI (100-200 mg) and RVP (200-400 mg) tasks from baseline (p < 0.05), but once controlled for the change-from-baseline caused by placebo, only the RTI simple reaction times showed significant improvements, following 100 mg (Δ = 16.3 ms, p = 0.009) and 200 mg (Δ = 16.9 ms, p = 0.009) of L-theanine.
Conclusions:
Consistent with our hypothesis, these findings suggest that L-theanine significantly improves attention in simple visuomotor tasks, but not in more complex sustained attention tasks, or executive control tasks that require top-down inhibition of pre-active responses.
... The content of L-theanine varies in different preparations of tea leaves [2,45]. Brewing time is also a major factor which could influence the amount of L-theanine extracted from a cup of tea [46], however, the maximum extraction does not seem to exceed 25 mg [2]. This dose, in a single cup of tea, was not found to show significant cognitive benefits [26]. ...
Tea (Camellia sinensis) is a historically and economically important beverage for Sri Lanka; and is traditionally believed to have relaxing or calming effects. Some evidence attributes these effects to a constituent of tea leaves; L-theanine, a non-protein-forming amino acid structurally similar to glutamic acid. Over the years, research has found L-theanine to also have effects on various cognitive functions, including attention. This review focuses on the research conducted thus far on the acute effects of L-theanine on neurobehavioral, neurophysiological, and functional neuroimaging indices, cognition and attention. Despite the heterogeneity of testing paradigms across studies, experimental evidence increasingly suggests that L-theanine could improve visual selective attention. Contrary to traditional belief, the amount of L-theanine in a cup of tea (4.5-22.5mg) seems to cause no significant effects; and attentional improvement is more prominent with much higher doses (100-500mg). This makes it worth exploring the possibility of enriching tea with L-theanine, while preserving the unique flavour of the product. L-theanine has an additive effect with caffeine in enhancing attention, but unlike caffeine, L-theanine can be ingested in high doses with no risk of adverse effects, tolerance or dependence. The evidence on attentional effects of L-theanine is almost entirely based on healthy samples who have undergone laboratory-based attentional tasks that employed abstract stimuli. When translating these laboratory findings to real-life scenarios, incorporating more real-life-based stimulus paradigms (i.e., simulated driving scenarios) is warranted. The clinical relevance of L-theanine research could also be improved by exploring the effects of L-theanine in cognitively compromised groups of individuals.
... L-theanine is a non-protein amino acid and chemically known as γ-glutamylethylamide. It is abundantly present in tea and 200 ml of black tea has been reported to contain about 25 mg of this amino acid (Keenan et al., 2011). L-theanine selectively inhibits the binding of glutamate to ionotropic receptors such as KA, AMPA and NMDA as well as metabotropic receptor type I that results in reduction of the influx of Ca 2+ (Deb et al., 2019). ...
Mitochondria are considered the only source of energy production within cells. This organelle is vital for neural function and survival by producing energy (adenosine triphosphate (ATP)) and regulating intracellular calcium. Mitochondrial dysfunction, which significantly contributes to both idiopathic and familial types of Parkinson’s disease (PD), depletes cellular energy, disrupts homeostasis, and induces oxidative stress, leading to cell death. In recent years several natural products have been discovered to be protective against mitochondrial dysfunction. This review discusses the role of mitochondria in the progression of PD to define the path for using natural products to prevent and/or cure PD.
Graphical abstract
... In our study, the contents of some amino acids (alanine, glutamic acid, glycine, serine, threonine and proline) increased in tea shoots harvested from soils treated with cow manure and urea, whereas the content of amino acids increased slowly in tea shoots harvested from soils treated with cow manure (Figure 3 and Table S2). This may influence the quality of green teas, because amino acids are the primary factor in the umami of tea infusions [19,20]. The sensory evaluation indicated that the scores of teas harvested during spring and late summer from soils treated with cow manure were higher than that of teas harvested from soils treated with urea. ...
Traditionally, the supplement of organic manure in tea plantations has been a common approach to improving soil fertility and promoting terroir compounds, as manifested by the coordinated increase in yield and quality for the resulting teas. However, information regarding the effect of organic manure in the metabolome of tea plants is still inadequate. The metabolite profiles of tea shoots applied with cow manure, urea or no fertilizer were studied using gas chromatography–mass spectrometry (GC–MS). In total, 73 metabolites were detected, and the modulated metabolites included mainly amino acids, organic acids and fatty acids. In particular, glutamine, quinic acid and proline accumulated more in tea shoots in soils treated with cow manure, but octadecanoic acid, hexadecanoic acid and eicosanoic acid were drastically reduced. Pearson correlation analysis indicated that organic acids and amino acids in tea shoots were the two major metabolite groups among the three treatments. The analysis of metabolic pathways demonstrated that the cow manure treatment significantly changed the enrichment of pathways related to amino acids, sugars and fatty acids. Sensory evaluation showed that the quality of green teas was higher when the plants used to make the tea were grown in soil treated with cow manure rather than urea during spring and late summer. The results indicated that the application of cow manure in soils changed the metabolic characteristics of tea shoots and improved the qualities of the resulting teas.
... Theanine (L-glutamyl ethylamide) is present in Japanese green tea and is one of the major components of amino acids [1]. Theanine is contained not only in green tea leaves but also in other tea leaves [2]. Drinking tea containing theanine has been found to have physiological effects: a relaxing effect, generation of an α-wave in the human brain [3], and reduction in blood pressure in rats with spontaneous hypertension and in high-stress-response adults [4][5][6][7]. ...
Background & objective
Theanine (L-glutamylethylamide) contained in green tea is a functional food component that has been attracting attention due to its relaxation effect. It was shown that the ingredients added to the theanine formulations increased the absorption of theanine. If this mechanism can be elucidated, it would be possible to contribute to development of evidence-based formulations. In this study, we investigated the effect of ingredients in the formulations on the absorption of theanine in detail.
Main methods
After oral administration of a mixture of theanine and additional components to Wistar rats the plasma concentration was determined by an HPLC and the pharmacokinetic parameters were calculated. In addition, a new system for evaluating intestinal blood flow was developed since the involvement of intestinal blood flow was considered as a factor that increased absorption of theanine.
Key findings
Plasma concentration of theanine increased significantly in the combined use group with eight ingredients containing piperine as compared with theanine only group. Piperine would increase theanine absorption by increased blood flow, not an inhibition of metabolism. We succeeded to develop a visual and quantitative system to evaluate the effect of these ingredients directly including piperine on the intestinal blood flow using indocyanine green while maintaining physiological conditions.
Significance
Increased intestinal blood flow by these ingredients including piperine enhanced the absorption of theanine. Other mechanisms may also be considered as the mechanism by which theanine absorption is increased in addition to increased blood flow.
... L-theanine can be daily supplemented through tea drinking, while the L-theanine content of tea varies considerably. Keenan et al. (2011) determined the amounts of L-theanine contained in commercially-available teas and found that a standard cup (200 mL) of green tea and black tea prepared under the regular brewing conditions contain around 8 and 25 mg L-theanine, respectively. After L-theanine was orally administrated, it can be quickly absorbed and transported through the brush-border membrane by a common Na(+)-coupled co-transporter in the intestine and enters systemic circulation (Kitaoka et al., 1996). ...
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.
... A cup of green tea contains about 25 mg of theanine. 25 Kuriyama et al. reported that people who drink green tea have less cognitive dysfunction. 9 In the previous report, the amount of theanine that led to an improvement in attentional function was 50.3 mg. ...
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.
... The stripping of the leaf epidermis and maceration during CTC step led to microstructural changes in cells which efficiently exposed its components. 37 The ndings in the present work support the reported theanine level (2.58-4.23 mg g À1 ) in twenty-seven famous commercial teas of UK. 38 Liu et al. reported higher levels of theanine (38.5-272 mg L À1 ) in green tea infusions determined by derivatization of infusion using 2,4-dinitro-uorobenzene, and detected at 360 nm using HPLC. 23 ...
The present study compares the effects of two green tea processing techniques, viz. orthodox and CTC (curl, tear and crush) on the quality parameters and sensory profiles under the geographical and climatic conditions of Assam, India. The results showed that CTC green tea infusions had 13.3, 7.5, 7.1, 9.8, 5.4, 17.3, 17.1 and 18.6% more total polyphenol, total catechin, (−)-epigallocatechin-3-gallate (EGCG), (−)-epicatechin-3-gallate (ECG), (−)-epigallocatechin (EGC), (−)-epicatechin (EC), water extract and theanine level, respectively than the infusions prepared from orthodox green tea. The sensory evaluation preferred the orthodox over CTC processing mode. Risk assessment with daily consumption of five cups (10 g) of green tea reveals that the EGCG level is free from the risk of hepatotoxicity and caffeine will not inflict any health hazard.
... L-theanine is a non-protein-forming amino acid structurally similar to glutamic acid. Naturally occurring in an edible form almost exclusively in tea (Camellia sinensis), the amount of L-theanine in drinking tea varies with the type and the brewing time: one cup of black tea contains 5-24 mg of L-theanine [1][2][3]. In rats, L-theanine peaks in plasma around 30 min after oral administration [4], crosses the blood-brain barrier [5], and is completely eliminated from plasma and the brain in 24 h [6]. ...
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.
... L-Tea plasma levels in humans after consuming 100 mg L-Tea (roughly equivalent to 4 cups of tea [28]) were measured to be about 25 µM [29,30], significantly lower than the concentrations needed to inhibit D-Ser uptake into SH-SY5Y cells in our experiments. On the other hand, plasma levels up to 13 mM and brain levels up to 2.3 mM were detected in rats after L-Tea administration [31]. ...
Decreased extracellular level of d-Serine (D-Ser), a co-agonist of the N-methyl-d-aspartate (NMDA) receptors was connected to receptor hypofunction in the brain and the related deficit of cognitive functions. Extracellular D-Ser concentration is modulated by ASCT neutral amino acid transporters. L-Theanine (L-Tea), a neutral amino acid component of green tea was reported to improve cognitive functions.
We thus intended to investigate the possible inhibitory effect of L-Tea on the D-Ser uptake of SH-SY5Y neuroblastoma cells, which was previously found as a good model of D-Ser transport into astrocytes.
Cells were incubated with D-Ser and various concentrations of L-Tea or the reference compound S-ketamine (S-Ket). The effect on the uptake was assessed by measuring the intracellular D-Ser concentration using a capillary electrophoresis–laser induced fluorescence detection method.
L-Tea competitively inhibited D-Ser uptake into SH-SY5Y cells with an IC50 value of 9.68 mM. Having previously described as an inhibitor of ASCT-2 transporter, S-Ket was intended to be used as a positive control. However, no acute inhibition of D-Ser transport by S-Ket was observed. Its long-term effect on the transport was also examined. No significant difference in D-Ser uptake in control and S-Ket-treated cells was found after 72 h treatment, although the intracellular D-Ser content of the 50 μM S-Ket pre-treated cells was significantly higher.
L-Tea was found to be a weak competitive inhibitor of the ASCT transporters, while S-Ket did not directly affect D-Ser uptake or modify the uptake kinetics after a long-term incubation period.
... Beside camellia sinensis, only certain mushrooms are known to contain it. In the case of black tea, 1 g should contain around 9 mg of Ltheanine [31,36]. Studies confirmed that the feeling of relaxation that is often linked with drinking tea could be lead back to L-theanine [1][2][3]32]. ...
We investigated caffeine and L-theanine, quality characteristics for camellia sinensis, in milled and ground black tea samples with near-infrared (NIR) spectroscopy giving a direct comparison between the performances of benchtop and handheld NIR spectrometers. The constructed partial least squares regression (PLSR) models for all spectrometers were validated by test-set-validation and according to the obtained root mean square errors of prediction (RMSEP) the performances of the spectrometers were as follows: The benchtop spectrometer NIRFlex N-500 (Büchi, Flawil, Switzerland) showed the best results for milled samples with a RMSEP of 0.14% for caffeine and 0.12% for L-theanine. For the ground samples, a RMSEP of 0.17% for caffeine and 0.12% for L-theanine was gained. While the handheld spectrometers MicroNIR 2200 (Viavi Solutions (former: JDS Uniphase Corporation), Milpitas, USA) and the microPHAZIR (Thermo Fisher Scientific, Waltham, USA) both provided good results for the prediction of caffeine in milled samples (RMSEP of 0.22% and 0.26%) only the microPHAZIR was able to satisfactorily determine the caffeine content in ground samples (RMSEP of 0.28%). The investigation of L-theanine with handheld spectrometers did not lead to convincing results, since R² was ca. 0.75 for milled samples while ground samples could not be calculated. Decisive differences were concluded in how different NIR instruments capture the chemical information on caffeine vs. L-theanine. The handheld spectrometers manifested limited applicability to L-theanine. Deeper insight was obtained through the detailed NIR band assignments of caffeine and L-theanine derived from quantum mechanical simulation. Narrow working spectral region of handhelds omits the characteristic absorption bands of L-theanine. Therefore, information on L-theanine content measured by the evaluated miniaturized spectrometers is insufficient to enable its effective quantification. In contrast, the most characteristic NIR absorption of caffeine matches the working spectral regions of the handheld NIR spectrometers, hence their performance is comparable with the benchtop device.
... Free amino acids are also found in tea, which can be altered via fermentation during the manufacturing process. 25 Among all these, nonproteinogenic L-theanine is the predominant amino acid (approximately 2À5 mg/g leaf) found in tea, which accumulates in higher contents in young and fresh tea leaves. 26 The highest content of L-theanine is determined in white tea and green tea followed by oolong tea and black tea. ...
Research on oxidative stress–related pathogenicities is gaining immense attention. Oxidative stress is induced by reactive species that are byproducts of biological metabolic reactions or arise due to environmental factors. Oxidative stress is crucial in cellular dysfunctions, wherein cellular components such as lipids, proteins, and nucleic acids are oxidized, thereby leading to several disorders including metabolic syndrome, cardiovascular disorders, neurodegenerative disorders, and cancer. Natural dietary antioxidants have been reported to reduce oxidative stress and to prevent associated diseases. Tea is considered as a predominant source of natural antioxidants. The major antioxidants present in tea include phenolic metabolites, although nonphenolic metabolites also possess prospective activity against oxidative stress. In this chapter, the role of oxidative stress–induced pathophysiology in several disorders is summarized, and the antioxidant potentialities of dietary antioxidants considering the phenolic and nonphenolic metabolites in tea have been described.
... Absorbance was registered at 210 nm. hypothetical slice of bread made with the mTG + C 2 H 5 NH 2 flour presents more theanine than a standard (200 mL) cup of black tea (24.2 ± 5.7 mg) or a cup of green tea (7.9 ± 3.8 mg) (Keenan, Finnie, Jones, Rogers, & Priestley, 2011). At this standpoint two conclusions can be drawn: 1, wheat flour can be enriched in L-theanine, a nutraceutical product with health benefits and used as an additive in food industry (Sharma et al., 2018); 2, it is possible that this previous modification of glutamine residues can hamper gluten digestibility, as well as tissue transglutaminase deamidation activity, which is a key step in the pathogenesis of celiac disease (Di Sabatino et al., 2012). ...
Functional foods have created an open environment for the development of new solutions to health-related issues. In celiac disease, there is still no therapeutic alternative other than the observance of a gluten-free diet. In this context, we developed a wheat flour enriched in L-theanine aimed to be a potential alternative to the gluten-free diet. Through microbial transglutaminase-catalysed transamidation of gluten proteins using ethylamine as amine nucleophile, substantial amounts of glutamine residues were converted in theanine residues. Furthermore, using T-cell lines generated from intestinal biopsy specimens of celiac disease patients, this treatment showed the potential to strongly reduce the ability of gluten proteins to stimulate a T-cell-mediated immune response. From a rheological point of view, the functionality of gluten was retained. Considering L-theanine’s evidence-based health benefits, a novel functional food is presented here and for celiac disease can be a path towards the development of an alternative to the gluten-free diet.
... Amino acids: In Gt and Bt, L-theanine is one of the most important amino acid and it accounts for almost 50% of the total free amino acids found in tea. It was irst discovered in an aqueous extract of Gt, later it was reported in Bt [84]. Reports suggest that theanine is synthesized in the tea roots and then proceeded to the developing shoot tips under the catalytic activity of a speci ic enzyme, L-glutamate ethylamine ligase and using the amino acid alanine as the precursor of ethyl-amide in presence of light [85]. ...
Tea (Black tea and Green tea) are one of the most widely consumed beverages in the world. However, with the increasing interest in the health properties of tea and a significant rise in scientific investigation, this review covers some of the recent findings on the health benefits of both green and black tea. The mechanisms of action of various black and green tea components have been presented. Green tea contains a unique set of catechins that responsible for its biological activity potentially relevant to the prevention of diseases. Although there has been much focus on the biological property of the major tea catechins, black tea offers major health benefits either due to the presence of the catechins in epimerized form or some other active components of both varieties of tea. Characteristics unrelated to the antioxidant properties of green and black tea might also be responsible for their therapeutic potential in preventing diseases. Synergistic effect of the tea constituents is increasingly recognized as being potentially important to the medicinal benefits of black and green tea. The studies indicate that tea has the potential of being a part of diet for healthy living.
Abbreviation: Bt, Black tea; Gt, Green tea; Tf, Theflavins; Tr, Thearubigins.
... Studies suggest that L-theanine may improve cognitive performance, and it is claimed that the combination of Ltheanine with caffeine allows the consumer to feel the positive cognitive effects of caffeine while counteracting the "jitters, " and reducing "mind wandering" (Bryan, 2008). The dosages vary between beverage and supplement choices, and so we provide a reference range to participants based on commonly consumed caffeinated drinks, available supplement dosages, and FDA compound review recommendations 4 (Keenan et al., 2011). ...
Background: The growing consumer digital tools market has made using individual health data to inform lifestyle changes more accessible than ever. The n-of-1 trial–a single participant, multiple crossover, comparative effectiveness trial–offers methodological tools that link interventions directly with personalized outcomes to determine the best treatment for an individual. We have developed a complete digital platform to support self-directed n-of-1 trials, comprised of virtual study on-boarding, visual informed consent, device integrations, in-app assessments, and automated data analysis. Objective: To evaluate the n-of-1 platform, a pilot study was launched to investigate the effects of commonly consumed substances on cognition. The purpose of the study is to allow an individual to measure the effect of 2 treatments (caffeine alone vs. caffeine + L-theanine) on 3 measures of cognitive performance: creative thinking, processing speed, and visual attention. Upon completion of the study, individuals receive personalized results that compare the impact of the two treatments on each of the cognitive performance measures. Methods: After the onboarding process, participants are randomized to a study length (5, 15, or 27 days), starting treatment (caffeine or caffeine + L-theanine), and app notification frequency (light, moderate). Each trial begins with a baseline period, during which participants abstain from either treatment, followed by 2 randomized counterbalanced treatment sequences (either ABBA or BAAB). Throughout the trial, daily tests assess participant cognitive performance. These tests are digital versions of the Remote Associates Test, Stroop Test, and Trail Making Test, and are implemented directly in the n-of-1 mobile application (“N1”). Assessments are completed at a fixed time, defined by the individual during study setup. Treatments are taken daily within a fixed time window prior to the user-defined assessment time. Cognitive assessment results are analyzed using a linear model with factors for treatment and block, and each treatment is compared to baseline. Results: We launched our N1 app on the Apple App Store in mid-October 2019 and recruited over 40 participants within the first month. Conclusion: This platform provides individuals the opportunity to investigate their response to treatments through n-of-1 methods, empowering them to make data-driven, personalized lifestyle choices. Trial Registration: www.ClinicalTrials.gov, identifier: NCT04056650.
... (2011) demleme süresinin artışı ile teanin miktarının arttığını ve bir kupa (200 mL) çayda yaklaşık 25 mg teanin bulunduğunu belirtmişlerdir. 7 Çaydaki teanin miktarı güneş ışığından etkilenmektedir; az güneş olan iklimlerde teanin konsantrasyonları daha yüksektir. 2 Teaninin kimyasal formülü C7H14N2O3, molekül ağırlığı ise 174,2 g/mol'dür. ...
L-teanin, başlıca yeşil, siyah, beyaz ve oolong çayın üretildiği Camellia sinensis yapraklarında bulunan ve çayın umami tadına katkı sağlayan özel bir amino asittir. Rahatlama, konsantrasyon ve öğrenme kabiliyetini geliştirme, nörolojik koruma, kafeinin olumsuz etkilerini azaltma, kan basıncını düşürme, vasküler hastalıkları önleme, antiobesite, antitümör ve antioksidan gibi pek çok farmakolojik ve biyoaktif etkileri olduğu belirtilmektedir. Biyolojik aktivitesini nitrik oksit üretimini ve glutatyon sentezini arttırarak ve inflamatuvar cevabı baskılayarak gösterdiği ifade edilmektedir. Teanin metabolizması ile ilgili kesin kanıta dayalı sonuç bulunmamakla birlikte etilamin ve glutamik aside metabolize edildiği ve idrarla atıldığı ileri sürülmektedir. Bu derlemenin amacı, ülkemizde oldukça fazla oranda tüketilen yeşil ve siyah çayda bulunan L-teaninin kimyasal ve fiziksel özelliklerini açıklayarak sağlık üzerine etkileri hakkında özet bilgi vermektir.
... Average L-theanine content per single cup of tea approximates 7.9-24.2 mg [21]. ...
Background
The aim of this study was to analyze the response of selected components of the immune system in rowers to maximal physical exercise, and to verify if this response could be modulated by supplementation with L-theanine.
Method
The double-blind study included 20 members of the Polish Rowing Team. The subjects were randomly assigned to the supplemented group (n = 10), receiving 150 mg of L-theanine extract for 6 weeks, or to the placebo group (n = 10). The participants performed a 2000-m test on a rowing ergometer at the beginning (1st examination) and at the end of the supplementation period (2nd examination). Blood samples were obtained from the antecubital vein before each exercise test, 1 min after completing the test, and after a 24-h recovery. Subpopulations of T regulatory lymphocytes (Tregs) (CD4+/CD25+/CD127-), cytotoxic lymphocytes (CTLs) (CD8+/TCRαβ+), natural killer (NK) cells (CD3-/CD16+/CD56+) and TCRδγ-positive (Tδγ) cells were determined by means of flow cytometry. The levels of interleukin 2 (IL-2), interleukin 4 (IL-4), interleukin 10 (IL-10), interferon gamma (INF-ɤ) and total antioxidant capacity (TAC) were determined with commercially available diagnostic kits.
Results
Supplementation with L-theanine contributed to a significant post-exercise decrease in IL-10 concentration, which was reflected by higher values of IL-2 to IL-10 and IFN-γ to IL-10 ratios. Moreover, a significant post-recovery decrease in CTL count, Treg to NK and Treg to CTL ratios was observed in the supplemented group.
Conclusion
Despite the decrease in the number of some cytotoxic cells (CTLs) and an increase in the proportion of Tregs to CTLs, supplementation with LTE seems to exert a beneficial effect on a disrupted Th1/Th2 balance in elite athletes, as shown by the decrease in IL-10 concentration.
... Diffusion of polyphenolic compounds, minerals, caffeine or theanine typical of tea infusions have been the subject of studies conducted by numerous authors [10][11][12]. According to Koch et al. [13,14] catechins are the major constituents responsible for properties and quality of green as well black teas. ...
Tea is one of the most popular drinks in the world, commonly consumed by consumers from all age groups mainly due to its refreshing taste, attractive aroma, and potentially beneficial impact on health. The composition of a tea drink depends on numerous factors, such as time and brewing temperature, degree of crumbling of tea leaves, and degree of mixing. Diffusion of the polyphenolic compounds, minerals, caffeine or theanine typical of tea infusions have been the subject of studies conducted by numerous authors. Promoting the extraction of amino acids from tea leaves when preparing infusions through the induction of a magnetic field constitutes not only another step towards the optimisation of the extraction process, but is also one of the methods to improve the nutritional value of tea infusions. The purpose of this work was to verify a hypothesis concerning the improvement of the extraction of amino acids from dried tea during the preparation of infusions by applying a permanent or variable magnetic field induced under laboratory conditions. A variable magnetic field applied as a factor assisting extraction resulted in an increased concentration in the total number of amino acids in green and black tea infusions. A statistically significant improvement in the level of free amino acids was observed after application of extraction assisted by a variable magnetic field with induction at 100 mT and a frequency of 50 Hz. Extraction using a variable magnetic field for tea infusions may constitute a good solution to assist traditional water extraction methods for research purposes.
... Addition of sugar during tea infusion preparation, however, did not significantly affect L-Th content. Higher content of L-Th was found in the cup prepared with vigorous agitation (Keenan, Mike, Jones, Rogers, & Priestley, 2011). Once tea is consumed, L-Th gets rapidly absorbed through microvilli via intestinal epithelial cells from where, it is transported to the brain tissues as it crosses the blood brain barrier. ...
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.
... Black tea contains considerably lower amounts of non-oxidised catechins as it is produced by allowing enzymatic oxidation to occur in harvested leaves of Camellia sinensis, resulting in fewer catechins (3-10%) due to the formation of thearubigins and theaflavins (12-18% and 3-6% respectively) (Chow and Hakim, 2011). It is noteworthy that the addition of milk-as is customary in black tea-can decrease both the antioxidant qualities of polyphenols (Bourassa et al., 2013) and-in elevated quantities (more than 50 ml in a 200 ml cup)-the concentration of l-theanine (Keenan et al., 2011). ...
Background:
Green tea (Camellia sinensis) is a beverage consumed for thousands of years. Numerous claims about the benefits of its consumption were stated and investigated. As green tea is experiencing a surge in popularity in Western culture and as millions of people all over the world drink it every day, it is relevant to understand its effects on the human brain.
Purpose:
To assess the current state of knowledge in the literature regarding the effects of green tea or green tea extracts, l-theanine and epigallocatechin gallate both components of green tea-on general neuropsychology, on the sub-category cognition and on brain functions in humans.
Methods:
We systematically searched on PubMed database and selected studies by predefined eligibility criteria. We then assessed their quality and extracted data. We structured our effort according to the PRISMA statement.
Outcome:
We reviewed and assessed 21 studies, 4 of which were randomised controlled trials, 12 cross-over studies (both assessed with an adapted version of the DELPHI-list), 4 were cross-sectional studies and one was a cohort study (both assessed with an adapted version of the Newcastle-Ottawa assessment scale). The average study quality as appraised by means of the DELPHI-list was good (8.06/9); the studies evaluated with the Newcastle-Ottawa-scale were also good (6.7/9).
Conclusions:
The reviewed studies presented evidence that green tea influences psychopathological symptoms (e.g. reduction of anxiety), cognition (e.g. benefits in memory and attention) and brain function (e.g. activation of working memory seen in functional MRI). The effects of green tea cannot be attributed to a single constituent of the beverage. This is exemplified in the finding that beneficial green tea effects on cognition are observed under the combined influence of both caffeine and l-theanine, whereas separate administration of either substance was found to have a lesser impact.
... L-theanine content of the extracts was determined by HPLC-DAD using a Hypersil ODS column (250 mm x 4.6 mm) [11]. Catechin content of the extracts were determined according to the standard ISO method (ISO14502-2, 2005) by HPLC-DAD using a Luna 5µ Phenyl-Hexyl column (250 mm x 4.6 mm). ...
Green tea (Camellia sinensis) contains bioactive compounds such as L-theanine and catechins with potential applications as food ingredients, nutraceuticals, dietary supplements, pharmaceuticals and cosmetic ingredients. L-theanine is an amino acid, which is responsible for the relaxation effect and " umami " taste of green tea. The antioxidant activity of catechins, the major phenolics in green tea, and their contribution to health effects of tea have been widely investigated. Green tea processing waste can be utilized as a source of these valuable compounds for the development of bioactive products. The aim of this study is to determine the optimum extraction conditions (temperature, time, flow rate) for the recovery of L-theanine and catechins from green tea waste using subcritical water extraction. Green tea waste (2 g) was extracted using a laboratory-built subcritical water extraction system to determine the effect of temperature (50-110°C) and flow rate (2-4 ml/min) on extraction yield at 1000 psi. Fractions were collected throughout the extraction as a function of time (up to 6 fractions for 60 min) and their L-theanine and catechin contents were analyzed using HPLC-PDA. Maximum L-theanine yield was obtained at 90°C in 60 min (2 ml/min) as 4.38±0.48 mg/g dry wt. 87% of this amount was recovered in the first 30 min of extraction. Flow rate effect was dependent on temperature. While a higher extraction rate was obtained at the start of the extraction at both temperatures at 4 ml/min, a crossover was observed at 90°C resulting in higher yields at 2 ml/min after 30 min of extraction. Similar yields were obtained at 110°C at the end of the extraction (after 30 min). Epigallocatechin gallate (EGCG), catechin (C), epicatechin (EC), epicatechin gallate (ECG), epigallocatechin (EGC), gallocatechin gallate (GCG) and gallocatechin (GC) were detected in the extracts. Recovery of theanine and catechins from green tea waste using a sustainable technology offers product development opportunities for various applications such as food ingredients and dietary supplements.
... -Theanine (γ-glutamylethylamide) is an unique, nonprotein forming amino acid, present in tea (Camellia sinensis (L.) O. Kuntze) 1,2 . It constitutes 1% to 2% of the total dry weight of tea leaves and about 50% of the total free amino acids 3 . ...
L-theanine, an important constituent of the tea, is consumed daily throughout the world and is said to greatly contribute to the umami taste of tea. The objective of this review is to summarize the currently available information of L-theanine with reference to health benefits. Relevant keywords like " Tea " , " L-theanine " and " health benefits " were used for the extraction and subsequent analysis of the biomedical literature in the field. Two search engines, Google and Pubmed were used for that purpose. It is expected that the review update the basic features of L-theanine as well as, the current status pertaining to the role of the L-theanine in human health.
... For instance, black tea has been shown to mitigate felt and physiological responses to stress (Steptoe et al. 2007), whereas coffee exacerbates the stress response (Lovallo et al. 2006). L-theanine, which is present in black, green, and white tea but not coffee (Keenan et al. 2011), may account for such reported differences. Theanine diminishes the stress response, reducing heart rate, blood pressure, cortisol, and perceived stress and anxiety (Kimura et al. 2007;Steptoe et al. 2007;Unno et al. 2013;Yoto et al. 2012). ...
Tea is perceived as more relaxing than coffee, even though both contain caffeine. L-theanine in tea may account for the difference. Consumed together, caffeine and theanine exert similar cognitive effects to that of caffeine alone, but exert opposite effects on arousal, in that caffeine accentuates and theanine mitigates physiological and felt stress responses. We evaluated whether caffeine and theanine influenced cognition under emotional arousal. Using a double-blind, repeated-measures design, 36 participants received 4 treatments (200 mg caffeine + 0 mg theanine, 0 mg caffeine + 200 mg theanine, 200 mg caffeine + 200 mg theanine, 0 mg caffeine + 0 mg theanine) on separate days. Emotional arousal was induced by highly arousing negative film clips and pictures. Mood, salivary cortisol, and visual attention were evaluated. Caffeine accentuated global processing of visual attention on the hierarchical shape task (p < 0.05), theanine accentuated local processing (p < 0.05), and the combination did not differ from placebo. Caffeine reduced flanker conflict difference scores on the Attention Network Test (p < 0.05), theanine increased difference scores (p < 0.05), and the combination did not differ from placebo. Thus, under emotional arousal, caffeine and theanine exert opposite effects on certain attentional processes, but when consumed together, they counteract the effects of each other.
... Depending on the variety of tea leaves and the duration of brewing, the amount of caffeine in a 200 ml cup of tea varies from 25 to 50 mg 3 and theanine from 4.5 to 22.5 mg. 2 Black tea is particularly high in theanine and a 200 ml cup contains about 24.5 mg of theanine. 4 The acute cognitive effects of caffeine on have been extensively studied. It is known to improve attention as indexed by improvement of reaction time in different paradigms that tax attentional resources to different levels viz. ...
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.
... L-theanine (γ-glutamylethylamide) is an amino acid primarily found in the green tea plant (Camellia sinensis) and is also present in other species of Camellia, as well as in the edible bay boletes mushroom Xerocomus badius. The L-theanine content of tea varies considerably, with estimates around 1%-2% of the dry weight of leaves [1,2] and a single cup of tea containing around 25 mg of L-theanine [3]. L-theanine has been shown to cross the blood-brain barrier, reaching peak concentrations in mammals between 30 and 120 min [4,5]. ...
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.
... The L-theanine of black tea in the current study was 10.2 mg/g in this study and was in agreement with those reported by [41] who report a mean L-theanine content of 9.1 mg/g. Thus, with 50 to 200 mg of L-theanine being reported to reduce blood pressure in animal models [44] and comparing to the L-theanine content of Kenyan green tea it means one should take more than 20 cups of tea in a day. ...
A study was carried out to quantitatively estimate the L-theanine content in 19 teas commercially available in the Kenyan market by High Performance Liquid Chromatography (HPLC). The test tea samples analyzed were green (n = 4), black (n = 8) and flavored (n = 7) teas from different origins viz., Kenya (n = 4), Uganda (n = 2), Tanzania (n = 5), Rwanda (n = 4), Cameroon (n = 1) and Sri-Lanka (n = 2) commercially available in the Kenyan market. The estimated Limit of Detection (LOD) of the current method was 0.01% L-theanine. The L-theanine content ranged from below the detection limit (<0.01% L-theanine) to 1.60% L-theanine on a dry weight (d.w) basis. Statisti- cally significant differences (p < 0.05) were observed in the L-theanine contents of black, green and flavoured teas. Rwandan green tea contained the highest L-theanine content with 1.60% d.w. whereas six of the seven flavoured teas had very low theanine levels (<0.01%) that could not be quantified by the current method.
... So, the content of free amino acids is the key factor of tea flavor. Because theanine is the largest amount of free amino acids, we are trying to explain the law of theanine release in the solution of several metal ions (Keenan et al., 2011). The thesis is trying to explain the law between the release of theanine and metal ions through designed model test. ...
Theanine is a main component in tea leaf, it is the key factor to influence the nutrition value and flavor when the tea leaf is brewing. Natural water is the most-used extractant to dissolve out the theanine. It is recorded in ancient books that dissolution rate is quite different in different kinds of natural water. Recent study shows its correlation with the complexing abilities of metal ions. The thesis is trying to explain the law between the release of theanine and metal ions through designed model test. Response surface experiments showed that in the mixed solution of 1.74 mg/L Ca2+, 21.63 mg/L Na+, 5.55 mg/L Mg2+ and 4.86 mg/L Al3+., the release of theanine reaches the peak value 0.88 mg/mL. It is also found that in the exist of Ca2+, free theanine is increasing with total metal ions while free theanine is decreasing with the increasement of total metal ions in the absence of Ca2+.
... The concentration of L-theanine, another interesting bioactive substance in tea, before and after fermentation process is denoted in Table 1. The average amount of theanine in black tea before fermentation amounted to 7.6 mg/g and literature values on tea range from 1.6 to over 18 mg/g [Keenan et al., 2011;Zhao et al., 2012]. Interestingly, theanine concentration has not been influenced by the fermentation process. ...
Extraction is a method often used to obtain products rich in bioactive compounds from plant material. Most of the solvents used for the polyphenols extraction simultaneously extract also sugars, undesirable as a component of health–promoting food. Fermentation might be a simple, cheap and efficient way of sugar elimination. In our study, black tea and goji berries, both known for their health benefits, were used and alcoholic fermentation by Saccharomyces cerevisiae was carried out to eliminate sugars. In the course of fermentation the concentration of polyphenols, L–theanine and carotenoids was evaluated in order to verify the preservation of selected bioactive compounds. Decreases in sugar content, formation of ethanol and yeasts growth were monitored during fermentation. The fermentation of black tea decreased the sugar concentration by 84% within 6 h without decreasing total polyphenols and L–theanine contents. Goji berry fermentation yielded a sugars decrease of 87% within 24 h, without decrease in polyphenol content. However, carotenoid content was reduced by 17%. The study showed that fermentation was an effective way to decrease sugar content in plant extracts, and therefore it might be a pertinent step to concentrate bioactives.
... Interventional, clinical data on green tea and cognition is limited to one specific compound present in green tea: the amino acid L-theanine. Theanine is extremely rare in the diet, however-while content is highly dependant on the specifics of preparation-green tea contains on average ~8 mg per 200 ml serving [79]. Park et al. [80] examined the impact of 1440 mg GTE+240 mg L-theanine isolate per day for sixteen weeks on cognitive function in Korean adults with mild cognitive impairment. ...
Green Tea Supplementation: Current Research, Literature Gaps, and Product Safety
This review broadly addresses the impacts of green tea (GT) and its extracts in a number of clinically-important areas, as listed below. It focuses on the available human research, and randomized, controlled trials, where possible. GT’s effects are not well established, due to the prevalence of conflicting data. It does appear that if GT is to have a positive effect on these outcomes, it likely needs to be in combination with caffeine.
... L-Theanine is a free amino acid found in Camellia species. Recent studies have found that L-theanine increases alpha waves, leading to relaxed yet alert state of mind, reduces both subjective and physiological stress responses during stressful situations and was found useful for reducing raised blood pressure (Keenan, Finnie, Jones, Rogers, & Priestley, 2011). Lower levels of theanine was found in teas made from anthocyanin-rich shoots compared to normal green shoots [GTP (1.07 ± 0.03%), BTP (0.85 ± 0.03%)] compared to GL (1.31 ± 0.03%), GT (1.12 ± 0.03%), and BT (0.94 ± 0.03%) and PL (1.16 ± 0.03%). ...
Recently anthocyanin-rich purple tea varieties have been developed. The quality of these new purple tea varieties developed in Kangra valley was assessed, and compared with the quality of tea from standard Kangra clone. Purple tea shoots (PL) recorded higher amount of polyphenols compared to standard green tea shoot (GL) while epigallocatechin gallate (EGCG) recorded higher levels in GL. Higher levels of theaflavins were recorded in orthodox black tea from purple shoots (BTP) compared to black tea (BT) made from green shoots. Both theanine and caffeine recorded higher levels in GL. Volatile flavour profiles of these teas showed qualitative and quantitative differences. Aroma extract dilution assay showed higher dilution factors in BTP than BT. Orthodox teas from purple shoots exhibited higher antioxidant activity compared to standard black tea. Strong correlation of total quality scores with aroma and infusion colour was observed. Tea from anthocyanin-rich cultivars can become specialty teas with high antioxidant activity.
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.
Objective:
This study investigated the association between serum ethylamine levels as an indicator of l-theanine consumption and the development of type 2 diabetes in a Japanese community.
Research design and methods:
A total of 2,253 community-dwelling Japanese individuals aged 40-79 years without diabetes were monitored for 7 years. Serum ethylamine levels were divided into quartiles: ≤0.86, 0.87-2.10, 2.11-5.28, and ≥5.29 ng/mL. Kinetic analysis of serum ethylamine concentrations was performed after ingestion of l-theanine-rich green tea products containing 8 mg of l-theanine by 12 healthy volunteers.
Results:
During follow-up, 282 subjects developed type 2 diabetes. The age- and sex-adjusted cumulative incidence of type 2 diabetes decreased significantly with elevating levels of serum ethylamine (P for trend = 0.04). This association remained unchanged after adjusting for potential confounding factors. The multivariable-adjusted hazard ratio (HR) for type 2 diabetes was significantly lower in the fourth quartile of serum ethylamine than in the first quartile (HR 0.69, 95% CI 0.49-0.98). This trend of decrease in diabetic risk across serum ethylamine levels was more prominent in middle-aged subjects and in subjects with prediabetes, obesity, or insulin resistance. Kinetic analysis estimated that the minimum concentration at the steady state was >5.90 ng/mL in the case of twice-daily ingestion with an interval of 12 h.
Conclusions:
Higher serum ethylamine was significantly associated with lower risk of the development of type 2 diabetes in a general Japanese population. The measurement of serum ethylamine concentration would be a useful biomarker for the objective estimation of l-theanine consumption.
Peptides could have specific tastes or bioactivities depending on the length and sequence of amino acids. Till date it remains unknown what peptides are formed during the white tea manufacturing process and whether they contribute to the flavor or bio-activities of white tea. As a first step to address these questions, we applied ultra-high pressure liquid chromatography coupled with quadrupole-orbitrap ultra-high resolution mass spectrometry (UPLC-Quadrupole-Orbitrap-UHRMS) to monitor peptides dynamic changes during the withering process. A total of 196 abundant peptides were identified. Most of them were oligopeptides within a molecular weight of 1000 Da. Four of them were randomly selected, synthesized peptides were applied for further confirmation and quantification. Sequence analysis suggested that some of them were potential taste contributors. Proteinase cleave site analysis identified two separate periods of active proteins degradation at 0–12 h and 30–42 h of the withering processes. Further analysis of cleavage sites also suggested that protein degradation during withering steps were random rather than a stepwise reaction.
Background:
The tea plant, Camellia sinensis (L.) O. Kuntz, is a perennial woody plant widely cultivated for the production of a popular non-alcoholic beverage. To rapidly identify and evaluate two different color tea varieties (yellowish and purplish), the main phenotypic traits and quality components were tested in this study. Then the metabolic profiles of tea shoots and leaves were analyzed using LC-MS/MS.
Results:
The yellowish variation had higher active level in catechins metabolism, and contents of luteolin and kaempferol 3-α-D-glucoside were much higher than others. But the purplish variation had low content of theanine and high content of caffeine. The contents of quercetin and kaempferol 3-α-D-galactoside were the highest in purplish leaves. Moreover, the yellowish variation had the highest total quality scores of green teas and black teas, while the purplish variation had the highest scores of oolong teas.
Conclusion:
Both the yellowish variation and the purplish variation were excellent breeding materials and worthwhile to breed new tea cultivars. The yellowish variation is more suitable to make high grade green teas or black teas, while the purplish variation is suitable to produce fine quality oolong teas.
Liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) is a primary tool for analysis of low volatility compounds in complex matrices. However, complex matrices, such as different types of tea, complicate analysis through ionization suppression or enhancement. In this study, sample preparation by a refined QuEChERS method combined with a dilution strategy removed almost all matrix effects caused by six types of tea. Tea samples were soaked with water and extracted with acetonitrile, cleaned up with a combination of PVPP (160 mg) and GCB (20 mg), and dried. Dried extracts were diluted with 20 mL acetonitrile/water (15:85, v/v) before analysis by UPLC-MS/MS. The average recoveries of eight neonicotinoid insecticides (dinotefuran, nitenpyram, thiamethoxam, imidacloprid, clothianidin, imidaclothiz, acetamiprid, and thiacloprid) ranged from 66.3 to 108.0% from tea samples spiked at 0.01-0.5 mg kg-1. Relative standard deviations were below 16% for all recovery tests. The limit of quantification ranged from 0.01 to 0.05 mg kg-1.
This study proposes a loose-leaf tea brewing service device with the added value of increasing tea drinking quality in our leisure life. The proposed device with multi-infusion timing control and user friendly interface characteristics utilizes AT89S51 programmable microcontroller to detect the input signals and trigger the corresponding outputs. The input signals come from a power switch for turning the controller on/off, three push buttons for setting the brewing time, and two other push buttons for controlling initial/extra brewing time setting and start/stop time control. The corresponding outputs include a power LED for indicating whether the controller is working or nonworking, a buzzer for reminding the completion of timing, and three 7-segment displays for showing the remaining time. Conclusively, the proposed microcontroller-based tea brewing service device can remind users remembering pour the water out timely, allow users to reset brewing time based on personal favorite tastes, and allow users to make the second or third rounds of tea infusion time for each individual setting. Therefore, the tea taste quality can be guaranteed.
Aluminium is reported to play an important role in the aetiology, pathogenesis and development of Alzheimer's disease (AD). Black tea (BT, Camellia sinensis, family - Theaceae) represents approximately 78% of total consumed tea in the world and possesses neuroprotective properties under conditions like hypoxia, ischaemia and Parkinson's disease. This research aimed to evaluate neuroprotective effect of black tea extract (BTE) on the cognitive deficits, activity of acetylcholinesterase (AChE), levels and activities of oxidant-antioxidant indices (thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx)), expressions of β amyloid 1-42 (Aβ1-42) synthesis related (amyloid precursor protein (APP), β and γ secretases) and apoptotic markers (Bax, Bcl-2, cyto c, caspases 3, 8 and 9) in hippocampus and cortex of aluminium chloride (AlCl3) induced AD rats. Chronic AlCl3 administration (100 mg/kg body weight i.p.) in Wistar rats for 60 days significantly enhanced the AChE activity, memory impairment, oxidative damage, Aβ burden and apoptosis markers. Co-administration of BTE to AlCl3 rats for 60 days significantly ameliorated the aluminium induced pathological changes. Thus, it is suggested that the anti-Alzheimer role of BTE may be attributed mainly to the active components present in black tea.
The main dietary sources of polyphenols are reviewed, and the daily intake is calculated for a given diet containing some common fruits, vegetables and beverages. Phenolic acids account for about one third of the total intake and flavonoids account for the remaining two thirds. The most abundant flavonoids in the diet are flavanols (catechins plus proanthocyanidins), anthocyanins and their oxidation products. The main polyphenol dietary sources are fruit and beverages (fruit juice, wine, tea, coffee, chocolate and beer) and, to a lesser extent vegetables, dry legumes and cereals. The total intake is ∼1 g/d. Large uncertainties remain due to the lack of comprehensive data on the content of some of the main polyphenol classes in food. Bioavailability studies in humans are discussed. The maximum concentration in plasma rarely exceeds 1 μM after the consumption of 10–100 mg of a single phenolic compound. However, the total plasma phenol concentration is probably higher due to the presence of metabolites formed in the body's tissues or by the colonic microflora. These metabolites are still largely unknown and not accounted for. Both chemical and biochemical factors that affect the absorption and metabolism of polyphenols are reviewed, with particular emphasis on flavonoid glycosides. A better understanding of these factors is essential to explain the large variations in bioavailability observed among polyphenols and among individuals.
An overview is given on the manufacture of the different types of tea along with the most important phenolics present in tea
and methods of analysis. Compositional data are presented for green, white and black teas. A differentiation of green and
black tea by using the ratio between total phenolics and sum of the major catechins seems to be feasible.
For white tea there is no general accepted definition. Possible approaches are geographic origin, the botanical variety and
the manufacture or the appearance. The differentiation between green and white teas by the ratio mentioned above is not possible.
Eswird eine Übersicht über die Teemanufaktur und die resultierenden Arten von Tee gegeben, begleitet von einer Übersicht über
einige wichtige Inhaltsstoffe (Flavanole, Zusammenstellung analytischer Methoden zur Bestimmung von (Poly)-phenolen und Daten
über grüne, schwarze undweiße Tees). Derzeit scheint eine Differenzierung von grünem und schwarzem Tee über das Flavanol:Gesamtphenolverhältnis
möglich.
Für weißen Tee gibt es derzeit keine allgemein akzeptierte Definition. Mögliche Ansätze für diese sind die geographische Herkunft,
die botanische Varietät oder die Art der Herstellung. Eine Differenzierung durch das Flavanol:Gesamtphenolverhältnis von grünem
und weißen Tee ist nicht realistisch.
Theanine, one of the main amino acid components in tea, is known as a precursor of the non‐peptide antigen ethylamine, which mediates a memory response leading to secretion of IFN‐γ. Tea which contains theanine is alleged to have various therapeutic benefits to man. Different types of tea contain various amounts of theanine. A method for reversed‐phase high performance liquid chromatographic separation of theanine with fluorescence detection and its application are described. The method was applied to determining theanine in different types and grades of tea samples, which were extracted in boiling water, followed by filtration through a 0.45 µm filter. Theanine was derivatized with o‐phthaldialdehyde (OPA) prior to analysis. Separation of theanine, using an isocratic elution with a mobile phase containing 15 mM sodium acetate, isobutanol, isopropanol, and acetonitrile (75∶3∶2.5∶8, pH 7.1) was achieved in less than ten minutes. The relative fluorescence of derivatized theanine remained steady during analysis. The limit of detection of theanine standard was 33.2 picograms, while the limit of quantitation of theanine in tea extract was about 0.33 ng/mL. The results show that there is a relative quantitative relationship between the degree of fermentation and the level of theanine. The findings indicate that non‐fermented green tea and partially fermented yellow tea contained more theanine than dark, black, and woo‐loong tea, which all undergo the fermentation.
Theanine was determined in black teas and tea plants by a combination method of thin-layer chromatography (t.l.c.) and densitometry. It was shown that in 20 samples of black tea from different qualities and sources the amount varied from 0.33 to 1.59 g 100 g−1 dry wt. The highest quality black teas possessed the lowest amount of theanine, but it is subject to chemical degradation during black tea manufacture. The investigation of physiological function of theanine in the tea plant showed that during germination the theanine level reached a maximum after 45 days. This indicates that at this period of the growth of the tea plant theanine acted as a source of nitrogen and as a starting point for the synthesis of the carbon skeletal compounds of the tea plant. Theanine was found to exist in all parts of the tea plant but it accumulated more in young and active tissues and also in younger plants, which emphasises its metabolic role in the tea plant. The distribution of theanine in the shoots indicated that the first leaf was the principal site for the synthesis of polyphenolic compounds from theanine.
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.
The qualitatively important components of green tea (theanine, caffeine, ascorbic acid, (−)-epicatechin, (−)-epigallocatechin, (−)-epicatechin gallate and (−)-epigallocatechin gallate) were analyzed simultaneously by using capillary electrophoresis. The running buffer used was borate buffer (80 mM, pH 8.4) containing 50 mM of sodium dodecylsulfate. The extracts of green tea, oolong tea and black tea were analyzed using this method. Green teas of different plucking dates and the leaf samples from different positions in one shoot were also measured using this method. These results showed that this method will considerably save time and labor for the analysis of these components, and is quite useful for the quality estimation of teas (particularly of green tea) and characterization of fresh tea leaves.
Dabsyl chloride (dimethylaminoazobenzene sulfonyl chloride), a useful chromophoric labeling reagent for amino acids and amines, was developed in this laboratory in 1975. Although several methods have been developed to determine various types of amino acids, a quick and easy method of determining theanine, GABA, and other amino acids has not been developed in one HPLC system. In this paper are analyzed the free amino acid contents of theanine and GABA in different teas (green tea, black tea, oolong tea, Pu-erh tea, and GABA tea) with a dabsylation and reverse phase high-performance liquid chromatography (HPLC) system coupled with a detector at 425 nm absorbance. Two reverse phase columns, Hypersil GOLD and Zorbax ODS, were used and gave different resolutions of dabsyl amino acids in the gradient elution program. The data suggest that the tea source or the steps of tea-making may contribute to the theanine contents variations. High theanine contents of high-mountain tea were observed in both green tea and oolong tea. Furthermore, the raw (natural fermented) Pu-erh tea contained more theanine than ripe (wet fermented) Pu-erh tea, and the GABA contents in normal teas were generally lower than that in GABA tea.
Modern chromatographic techniques such as high-performance liquid chromatography are currently the most helpful approach to the routine analysis of and research of non-volatile tea constituents. Using these techniques some errors in the more classical analytical techniques could be detected. Unfortunately, some of these methods of analysis are still in widespread use, even as official methods. However, knowledge of especially the polyphenols in tea is still lacking, and for many of the minor polyphenols no chromatographic methods for the determination exist.
The main dietary sources of polyphenols are reviewed, and the daily intake is calculated for a given diet containing some common fruits, vegetables and beverages. Phenolic acids account for about one third of the total intake and flavonoids account for the remaining two thirds. The most abundant flavonoids in the diet are flavanols (catechins plus proanthocyanidins), anthocyanins and their oxidation products. The main polyphenol dietary sources are fruit and beverages (fruit juice, wine, tea, coffee, chocolate and beer) and, to a lesser extent vegetables, dry legumes and cereals. The total intake is approximately 1 g/d. Large uncertainties remain due to the lack of comprehensive data on the content of some of the main polyphenol classes in food. Bioavailability studies in humans are discussed. The maximum concentration in plasma rarely exceeds 1 microM after the consumption of 10-100 mg of a single phenolic compound. However, the total plasma phenol concentration is probably higher due to the presence of metabolites formed in the body's tissues or by the colonic microflora. These metabolites are still largely unknown and not accounted for. Both chemical and biochemical factors that affect the absorption and metabolism of polyphenols are reviewed, with particular emphasis on flavonoid glycosides. A better understanding of these factors is essential to explain the large variations in bioavailability observed among polyphenols and among individuals.
The effects of product and preparation variables on the in-cup chemical composition of tea extracts is of interest because the appearance and taste characteristics and the possible health effects of a tea liquor arise from the chemical components extracted from the leaf during tea preparation. A comprehensive study was therefore undertaken to determine the contributions of product and preparation variables on the total soluble solids, caffeine, and polyphenol contents of tea extracts. The results of this study show that the variety, growing environment, manufacturing conditions, and grade (particle size) of the tea leaves each influence the tea leaf and final infusion compositions. In addition, the composition of the tea infusion was shown to be influenced by whether the tea was contained in a teabag and, if so, the size and material of construction of the bag. Finally, the preparation method, including the amounts of tea and water used, infusion time, and amount of agitation, was shown to be a major determinant of the component concentrations of tea beverages as consumed. An illustration of the variation introduced by these product and preparation factors is provided by comparing solids, caffeine, and polyphenol contents of green and black tea infusions when commercial products are prepared according to the instructions given on their packaging.
L-Theanine is an amino acid contained in green tea leaves which is known to block the binding of L-glutamic acid to glutamate receptors in the brain. Because the characteristics of L-Theanine suggest that it may influence psychological and physiological states under stress, the present study examined these possible effects in a laboratory setting using a mental arithmetic task as an acute stressor. Twelve participants underwent four separate trials: one in which they took L-Theanine at the start of an experimental procedure, one in which they took L-Theanine midway, and two control trials in which they either took a placebo or nothing. The experimental sessions were performed by double-blind, and the order of them was counterbalanced. The results showed that L-Theanine intake resulted in a reduction in the heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress task relative to the placebo control condition. Moreover, analyses of heart rate variability indicated that the reductions in HR and s-IgA were likely attributable to an attenuation of sympathetic nervous activation. Thus, it was suggested that the oral intake of L-Theanine could cause anti-stress effects via the inhibition of cortical neuron excitation.
Two liquid chromatographic methods that involve precolumn derivatization with o-phthaladehyde (OPA) and phenylisothiocyanate (PITC) with fluorescence and diode array UV detection for the determination of theanine have been developed. The chromatographic separations were achieved by reverse-phase high-performance liquid chromatography using octadecyl columns and gradient elution. The methods were applied to evaluate the theanine content of commercial tea leaves. The coefficient of variation of the peak area repeatability for within day (n = 8) and between day (n = 8 over 10 days) was lower than 3% for both of the methods. The estimated limit of detection (LOD) and limit of quantitation (LOQ) for the OPA method was 0.12 and 0.35 microg theanine, respectively. The PITC method was 500-fold more sensitive with LOD and LOQ values of 0.25 and 0.75 ng, respectively. The theanine content of the commercial tea samples varied from 2-5 mg/g leaf. The overall % recoveries for these methods ranged from 93-99.3. The sensitivity and simplicity of the method render them suitable for use in quality control laboratories.
Epidemiological studies assessing the health benefits of drinking black tea are equivocal. Such disparity may reflect an inability of semiquantitative assessment to consider how infusion time and addition of milk affect the bioavailability of potentially beneficial antioxidant polyphenols. Six brands of tea demonstrated similar increases in antioxidant capacity and total phenolic and catechin contents with increasing infusion time. These results were unaffected by the addition of milk. Consumption of black tea (400 mL) was associated with significant increases in plasma antioxidant capacity (10%) and concentrations of total phenols (20%), catechins (32%), and the flavonols quercetin (39%) and kaempferol (45%) (all p < 0.01) within 80 min. This was unaffected by adding milk. Infusion time may therefore be a more important determinant in the absorption of polyphenols from black tea. Observational studies assessing the health benefits of tea consumption require recording of brewing methods as well as frequency of consumption.
In this paper, the differentiation of green, black, Oolong, white, and Pu-erh teas has been carried out according to their free amino acid contents. Alanine, arginine, asparagine, aspartic acid, glutamic acid, isoleucine, histidine, leucine, phenylalanine, serine, theanine, threonine, and tyrosine have been determined by liquid chromatography with derivatization with o-phthalaldehyde and fluorescence detection. The chromatographic separation was achieved with a Hypersil ODS column and gradient elution. The amino acid contents were used as chemometric descriptors for classification purposes of different tea varieties. Principal component analysis, k-nearest neighbors, linear discriminant analysis, and artificial neural networks were applied to differentiate tea varieties. Using back-propagation multilayer perceptron artificial neural networks, 100% success in the classification was obtained. The most differentiating amino acids were glutamic acid, asparagine, serine, alanine, leucine, and isoleucine.
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.
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.
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.
Perfect cuppa, how to make it
- Tetley Tea
Tetley Tea. Perfect cuppa, how to make it. http://www.tetley.co.uk/why-tea-isgreat/perfect-cuppa/how-to-make-it (accessed June 10, 2009).
The effects of theanine on sleep with physiological evaluation using actigraph
- M Ozeki
- L R Juneja
- S Shirakawa
Ozeki, M., Juneja, L. R., & Shirakawa, S. (2003). The effects of theanine on sleep with
physiological evaluation using actigraph. Proceedings of the 50th meeting of
Japan Society of Physiological Anthropology, Chiba, October 25-26.