Review of Scientific Research on matcha tea

Par Valentin Van Nhut

Bienfaits / Effets sur la Santé

Welcome to our selection of items and reports on scientific and medical research on tea (green tea, black tea, white tea) and more specifically matcha green tea (in Japanese, "抹茶", pronounced phonetically [mat.tɕa]) — which is, in simple terms, ground green tea powder.

Please note that this selection—organised by theme and chronology of scientific studies on matcha—is continuously updated with items selected by the Kumiko Matcha team. We invite you to bookmark this page or visit it regularly to stay informed about the latest scientific research on matcha.

Finally, it is important to note that all sources cited in this report—an overview of scientific research on matcha—come from academic publications, clinical studies, and international scientific research, including many reputable publications such as: The New England Journal of Medicine (NEJM), PLoS Medicine, The American Journal of Clinical Nutrition, Journal of the American Medical Association (JAMA), Nature, The Lancet, British Medical Journal (BMJ), etc.

Warning: The Kumiko Matcha editorial team provides free information in this dossier based solely on studies of high quality in terms of methodology (primary outcome measures, bias, etc.). Furthermore, this information may change over time as research progresses. Consequently, Kumiko Matcha is not responsible for the contents and hyperlinks of the sources, their modification and conclusions, and has no economic or professional ties to the authors of the searches.

Summary

I. Matcha is considered a superfood.

The global popularity of Japanese matcha has skyrocketed in recent years, mainly as a superfood (« functional food ») and as a component of certain dietary supplements.

II. Press review on scientific research

Studies on matcha and its components have revealed a wide variety of benefits, showing that it can help protect the liver, promote heart health, and even help with weight loss as part of a healthy, balanced diet.

III. The scientifically proven benefits of matcha

An ancient beverage, matcha green tea comes from the same plant as traditionally consumed green tea, but it is made using a specific and precise process from the whole leaf, which is the subject of increasing research.

IV. Summary of what science says about matcha

Discover the main benefits of matcha for wellbeing and as a functional food to help improve overall health, through several scientific studies.

V. Matcha and diet

Green tea is a "fat burner": it increases fat burning and promotes weight loss. This makes matcha an interesting functional food as part of a healthy, balanced diet and weight management.

Green tea increases fat burning and weight loss.

VI. Matcha and wellbeing

Advances in medical imaging show that green tea has effects on the brain and helps improve memory and focus. It is also recognised to help maintain a high level of alertness and can counteract the damage caused by oxidative stress in some individuals.

Green tea has effects on the brain and helps improve memory.
Green tea contributes to good oral hygiene.
Green tea helps maintain a high level of alertness.
The importance of storing matcha green tea properly.
Green tea counteracts damage caused by oxidative stress.
Green tea helps reduce inflammation caused by UV rays.

VII. Matcha and medical research

Modern science has helped us better understand the health benefits of matcha. Some studies have even shown that green tea helps fight neurodegenerative diseases, improves mental health, and contributes to the prevention of certain long-term illnesses and conditions.

Green tea helps fight neurodegenerative diseases.
Green tea helps prevent certain diseases and conditions.
Matcha green tea helps prevent type 2 diabetes.
Matcha green tea powder affects substrate oxidation.
Green tea consumption and colorectal cancer risk in Japan.
Drinking green tea may reduce the risk of heart attacks.
Green tea helps prevent glaucoma and promotes eye health.
Green tea EGCG as an adjunctive treatment in HIV-1.

Green tea fields in Japan

Tea fields (Camellia sinensis) before harvest.

Matcha is considered a superfood.

The global popularity of Japanese matcha has skyrocketed in recent years, mainly as a superfood (also called "functional food") and as an ingredient in certain dietary supplements.

Far from its original image associated with the Japanese tea ceremony, it is now used in many recipes (matcha latte, shake, matcha ice cream, etc.) and available in several organic and natural food stores, restaurants, pastry shops, ice cream parlors, tea rooms, and coffee shops.

Highly photogenic, with an intense, electric green colour that has even influenced fashion and design (decor, perfumery, etc.), matcha green tea is also a popular food on social media, particularly Instagram. This craze spans generations and cultures, adapting to different consumption patterns. In fact, there is no such thing as a typical matcha tea consumer, even though this superfood comes at a certain cost and is aimed particularly at people with a wellbeing-oriented lifestyle.

Like classic green tea, matcha green tea powder comes from the Camellia sinensis plant, but it is grown differently and has a unique nutritional profile that is recognised for contributing to better balance and overall wellbeing. Japanese tea producers cultivate the tea plants used to produce matcha by covering their Camellia sinensis plants for an average of 20 to 30 days before harvest to avoid direct sunlight.

This crucial step in the production of matcha green tea increases chlorophyll production, gives the plant a darker green hue, and increases the content of several components, including amino acids (L-theanine, glutamic acid, ethylamide, etc.).

Japanese matcha production

Traditional Japanese matcha production.

Once the green tea leaves have been harvested, the stems and veins are removed and the leaves are ground (very slowly to avoid oxidizing the precious organic components) into a fine powder using a stone mortar - an ishiusu ("石臼").

These ancestral matcha production techniques give this type of matcha tea increased antioxidant power, which several studies regularly reveal.

As a result, matcha powder contains the nutrients of the entire tea leaf, which translates into a higher quantity of caffeine (also called "theine," "1,3,7-trimethylxanthine," "methyl theobromine"), and antioxidants than is typically found in green tea, black tea, or white tea.

Press review on scientific research

Press review on scientific, medical, and nutritional research on matcha green tea

EGCG, L-theanine, etc.: matcha green tea is packed with components that are beneficial to health and wellbeing.

The main purpose of this press review is therefore to compile a list of the most relevant studies on the health benefits of matcha green tea, all based on science.

It should be noted that many items are initially published in English (the reference language for international research), but summaries of these items are available in French to help you better understand the results of the various studies.

In this way, Kumiko Matcha offers informative contents and reliable sources that are not intended to replace the relationship between a healthcare professional and their patient, but to improve understanding of study results.

Matcha farm in Japan

Tea plants.

Finally, the editorial team of the Kumiko Matcha website has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutes, medical associations, scientific journals, and experts.

We also emphasize this approach by regularly conducting analyses on the different matcha teas we sell in our shop. In addition to complying with current regulations on food hygiene and imported foodstuffs, Kumiko Matcha is a certified organic operator in accordance with EU organic regulations by the certification body FR-BIO-10, certificate CER-OPT114307-C199816.

Kumiko Matcha does not provide medical advice, and none of the information (text, links, images) available on the website can, in any way, answer specific medical questions. The contents (nutritional and health claims) are intended for informational purposes only and do not replace the advice, diagnosis, or treatment provided by a healthcare professional. If you have any questions about your health, please speak directly to your doctor or pharmacist.

Scientific search on green tea

The benefits of matcha proven by science

Matcha green tea comes from the same plant as traditionally consumed green tea, but it is made using a specific and precise process from the whole leaf.

As a result, matcha green tea powder contains a much higher quantity of antioxidants and plant compounds beneficial to human health than any other type of tea (green tea, black tea, white tea).

Studies have revealed a variety of health benefits associated with matcha and its components, ranging from improved focus and weight loss to a reduced risk of heart disease.

Matcha tea is also a simple drink to prepare, which can easily be incorporated into a balanced diet for healthy young adults and adults (unless contraindicated).

Summary of what science says about matcha

Matcha contains a concentrated quantity of antioxidants, which can reduce cell damage and prevent chronic diseases.
Some studies have shown that matcha may not prevent liver damage but may reduce the risk of liver disease. However, further studies are needed to examine the effects on humans in the general population.
Matcha has been shown to improve attention, memory, and reaction time. It also contains caffeine and L-theanine (theanine), which can improve several aspects of brain function.
Studies on test tubes and animals have shown that matcha compounds can inhibit the growth of cancer cells.
Studies show that green tea and matcha powder can reduce several risk factors for heart disease.
Some studies show that green tea extract helps increase metabolism and fat burning, both of which can promote weight loss.

Please note: It is important to note that there are many ways to prepare matcha green tea, allowing this green tea powder to be incorporated into a range of different and interesting recipes. However, depending on the preparation methods (water temperature, hygiene, etc.) and the ingredients used (sugars, milk, etc.), the benefits of matcha can vary greatly or even be altered.

Matcha and diet

Green tea increases fat burning and promotes weight loss.

December 1999 - Abdul G Dulloo, Claudette Duret, Dorothée Rohrer, Lucien Girardier, Nouri Mensi, Marc Fathi, Philippe Chantre, Jacques Vandermander, Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans, The American Journal of Clinical Nutrition, Volume 70, Issue 6, December 1999, Pages 1040–1045, https://doi.org/10.1093/ajcn/70.6.1040.

This clinical study tested the hypothesis that catechin-type polyphenols contained in green tea extract increase energy expenditure and fat oxidation over a 24-hour period. Their conclusion shows that green tea has thermogenic properties and the ability to burn more fat than a placebo, and that these properties are directly due to the catechins contained in green tea. The American Journal of Clinical Nutrition recently published a press release at the International Tea & Human Health Symposium showing that tea promotes weight loss, improves heart health, and slows the progression of prostate cancer. Background: Current interest in the role of functional foods in weight control has focused on plant ingredients capable of interfering with the sympathoadrenal system. Objective: We investigated whether green tea extract, due to its high content of caffeine and catechins, could increase 24-hour energy expenditure (EE) and fat oxidation in humans. Design: 24-hour EE, respiratory quotient (RQ), and urinary nitrogen and catecholamine excretion were measured in a respiratory chamber in 10 healthy men. On three occasions, subjects were randomly assigned to one of three treatments: green tea extract (50 mg caffeine and 90 mg epigallocatechin gallate), caffeine (50 mg), and placebo, which they ingested at breakfast, lunch, and dinner. Results: Compared with placebo, treatment with green tea extract resulted in a significant increase in 24-hour EE (4%; P <0.01) and a significant decrease in 24-hour QR (from 0.88 to 0.85; P <0.001) without any change in urinary nitrogen. Twenty-four-hour urinary norepinephrine excretion was higher during treatment with green tea extract than with placebo (40%, P <0.05). Treatment with caffeine in quantities equivalent to those found in green tea extract had no effect on EE and RQ or on urinary nitrogen or catecholamines. Conclusions: Green tea has thermogenic properties and promotes fat oxidation beyond that explained by its caffeine content alone. Green tea extract may play a role in controlling body composition via sympathetic activation of thermogenesis, fat oxidation, or both.

October 2007 - Auvichayapat P, Prapochanung M, Tunkamnerdthai O, Sripanidkulchai BO, Auvichayapat N, Thinkhamrop B, Kunhasura S, Wongpratoom S, Sinawat S, Hongprapas P. Effectiveness of green tea on weight reduction in obese Thais: A randomized, controlled trial. Physiol Behav. 2008 Feb 27;93(3):486-91. doi: 10.1016/j.physbeh.2007.10.009. Epub 2007 Oct 18. PMID: 18006026.

60 obese Thai people participated in this study to explore the effects of green tea on weight loss. This study was undertaken to investigate the effects of green tea on weight reduction in obese Thai people. A randomized controlled trial involving 60 obese subjects (body mass index, BMI> 25 kg/m2) was conducted. All subjects consumed a Thai diet containing 3 meals (8373.6 kJ/day) for 12 weeks, prepared by the nutrition unit of Srinagarind Hospital. The diet contained 65% carbohydrates, 15% protein, and 20% fat. Body weight, BMI (body mass index), body composition, resting energy expenditure, and substrate oxidation were measured at baseline and during weeks 4, 8, and 12 of the study. Serum leptin and urinary VMA (vanillylmandelic acid) levels were measured at baseline and during week 12. Differences over time and between treatments (green tea or placebo) over time were determined using a two-factor ANOVA with repeated measures. Comparing the two groups, differences in weight loss were 2.70, 5.10, and 3.3 kg during weeks 4, 8, and 12 of the study, respectively. At weeks 8 and 12 of the study, body weight loss was significantly different (P < 0.05). At week 8, the difference in resting energy expenditure was 183.38 kJ/day (P < 0.001), the difference in respiratory quotient was 0.02 (P < 0.05), and no significant differences existed in satiety score, food intake, or physical activity. Urinary VMA was significantly different at week 12 of the study (P <0.05). "We conclude that green tea can reduce body weight in obese Thai subjects by increasing energy expenditure and fat oxidation."

July 2009 - Hursel R, Viechtbauer W, Westerterp-Plantenga MS. The effects of green tea on weight loss and weight maintenance: a meta-analysis. Int J Obes (Lond). 2009 Sep;33(9):956-61. doi: 10.1038/ijo.2009.135. Epub 2009 Jul 14. PMID: 19597519.

Introduction: Different results on the effect of green tea on weight loss (WL) and weight maintenance (WM) have been reported in studies with subjects differing in ethnicity and habitual caffeine consumption. Objective: To elucidate through meta-analysis whether green tea does indeed have a role in body weight regulation. Methods: Studies in English on MW and MW after green tea supplementation were identified by PubMed and based on references from retrieved articles. Of the 49 studies initially identified, a total of 11 articles met the inclusion criteria and provided useful information for meta-analysis. Effect sizes (mean weight change in the treatment group compared to the control group) were calculated and aggregated using a random-effects model. The influence of several moderators on effect sizes was examined. Results: Catechins significantly decreased body weight and significantly maintained body weight after a period of WL (microcirc = -1.31 kg; P <0.001). Inhibition of this effect by high habitual caffeine intake (>300 mg per day) did not reach significance (microcirc = -0.27 kg for high intake and microcirc = -1.60 kg for low habitual caffeine intake; P = 0.09). Furthermore, the apparently weaker effect of catechins in Caucasian subjects (microcirc = -0.82 kg) compared to Asian subjects (microcirc = -1.51 kg; p = 0.37) did not reach significance. The interaction of ethnicity and caffeine consumption was a significant moderator (p = 0.04). Conclusions: Catechins or a mixture of epigallocatechin gallate (EGCG)-caffeine have a slight positive effect on BW and BMR. The results suggest that habitual caffeine intake and ethnicity may be moderators, as they may influence the effect of catechins.

January 2012 - Ying Zhang, Yingjie Yu, Xu Li, Shinichi Meguro, Satoshi Hayashi, Mitsuhiro Katashima, Takeshi Yasumasu, Jingzhong Wang, Keji Li. Effects of catechin-enriched green tea beverage on visceral fat loss in adults with a high proportion of visceral fat: A double-blind, placebo-controlled, randomized trial. Journal of Functional Foods, Volume 4, Issue 1, 2012, Pages 315-322, ISSN 1756-4646, https://doi.org/10.1016/j.jff.2011.12.010. (https://www.sciencedirect.com/science/item/pii/S1756464611001162)

118 obese Chinese people participated in this study, which compared the results of daily consumption of a catechin-enriched green tea drink with a "control" drink. After 12 weeks, the results showed that the group tested with catechin lost more visceral fat, particularly in the abdominal region. The effects of catechin-enriched green tea on Chinese adults with a high proportion of abdominal visceral fat were evaluated. The subjects (118) were randomly assigned to consume a beverage containing 609.3 mg of catechins and 68.7 mg of caffeine or a control beverage daily for 12 weeks. Abdominal fat area, body weight, and composition were measured at week 0, week 8, and week 12. One hundred and four subjects completed the trial. Mean visceral fat area, body weight, and body fat were significantly reduced by the catechin-enriched green tea treatment, but these effects were not observed in the control group with per-protocol set analysis. The decrease in visceral fat area at week 12 in the catechin group was greater than that in the control group (P = 0.04). Thus, consumption of the catechin-enriched green tea beverage for 12 weeks induced visceral fat loss in Chinese adults with a high proportion of abdominal visceral fat.

Matcha and wellbeing

Green tea has effects on the brain and helps improve memory and focus.

August 2008 - Owen GN, Parnell H, De Bruin EA, Rycroft JA. The combined effects of L-theanine and caffeine on cognitive performance and mood. Nutr Neurosci. 2008 Aug;11(4):193-8. doi: 10.1179/147683008X301513. PMID: 18681988.

The combined effects of L-theanine and caffeine show a significant improvement in mood and focus compared to a placebo. The aim of this study was to compare 50 mg of caffeine, with and without 100 mg of L-theanine, on cognition and mood in healthy volunteers. The effects of these treatments on word recognition, rapid visual information processing, critical flicker fusion threshold, attention shifting, and mood were compared to a placebo in 27 participants. Performance was measured at baseline and again 60 min and 90 min after each treatment (separated by a 7-day washout period). Caffeine improved subjective alertness at 60 min and accuracy on the attention switching task at 90 min. The combination of L-theanine and caffeine improved both speed and accuracy on the attention switching task at 60 min and reduced sensitivity to distracting information on the memory task at 60 min and 90 min. These results replicate previous evidence suggesting that L-theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks.

August 2013 - Zhang Q, Yang H, Wang J, et al. Effect of green tea on reward learning in healthy individuals: a randomized, double-blind, placebo-controlled pilot study. Nutr J. 2013;12(1):84. doi: 10.1186/1475-2891-12-84.

Green tea (Camelia sinensis) is one of the most popular beverages in both the Eastern and Western worlds. There is growing evidence that green tea extracts and their main component, epigallocatechin gallate (EGCG) polyphenol, have multiple health benefits, such as anti-stress, anti-cancer, and antioxidant effects. In particular, a recent survey found that higher green tea consumption was associated with a lower prevalence of depressive symptoms in Japanese elderly people. In addition, a preclinical study demonstrated that green tea had antidepressant-like effects. These results suggest that there may be a link between green tea consumption and depressive symptoms. However, the underlying mechanism involved in the treatment of depression with green tea in clinical settings has not been well studied. To contribute to the scientific literature on this topic, a recent study reveals the effects of green tea on reward learning in healthy individuals (a randomized, double-blind, placebo-controlled pilot study). Reward learning is a type of reinforcement learning—a process by which organisms acquire information about stimuli, actions, and contexts that predict positive results. Background: Clinical and preclinical studies have found that regular consumption of green tea reduced the prevalence of depressive symptoms and produced antidepressant-like effects in rodents. Evidence suggests that disrupted reward learning has been associated with the development of anhedonia, a core symptom of depression. However, the relationship between green tea and reward learning is poorly studied. "Our objective was to test whether chronic green tea treatment in healthy subjects affects the reward learning process and subsequently regulates depressive symptoms." Methods: Seventy-four healthy subjects participated in a randomized, double-blind, placebo-controlled study with oral administration of green tea or placebo for 5 weeks. "We used the monetary incentive delay task to assess reward learning by measuring the response to the reward trial or the no-reward trial. We compared the reaction time of reward responsiveness between green tea and placebo treatment. In addition, we selected the Montgomery-Asberg Depression Rating Scale (MADRS) and the 17-item Hamilton Depression Rating Scale (HRSD-17) to estimate depressive symptoms in these two groups." Results: The results showed that chronic green tea treatment increased reward learning compared to placebo by decreasing reaction time in the monetary incentive delay task. In addition, participants treated with green tea showed reduced scores measured in MADRS and HRSD-17 compared to participants treated with placebo. Conclusions: "Our results reveal that chronic green tea increased reward learning and prevented depressive symptoms. These results also raised the possibility that supplemental green tea administration may reverse the development of depression through the normalization of reward function."

December 2013 - Juszkiewicz A, Glapa A, Basta P, et al. The effect of L-theanine supplementation on the immune system of athletes exposed to strenuous physical exercise. J Int Soc Sports Nutr. 2019;16(1):7. Published 2019 Feb 15. doi:10.1186/s12970-019-0274-y

A clinical study shows that L-theanine boosts the immune system and stimulates the production of alpha waves in the brain, which are responsible for a state of deep relaxation and mental clarity. Here is an excerpt that explains the different types of waves produced by the brain. Background: The aim of this study was to analyse the response of certain components of the immune system in rowers to maximal physical exercise and to verify whether this response could be modulated by L-theanine supplementation. Method: The double-blind study included 20 members of the Polish rowing team. Subjects were randomly assigned to either the supplementation group (n = 10), receiving 150 mg of L-theanine extract for 6 weeks, or the placebo group (n = 10). Participants realised a 2000 m test on a rowing ergometer at the beginning (1st examination) and at the end of the supplementation period (second examination). Blood samples were taken from the antecubital vein before each exercise test, 1 minute after the end of the test, and after a 24-hour recovery period. Subpopulations of regulatory T cells (Tregs) (CD4+/CD25+/CD127-), cytotoxic lymphocytes (CTLs) (CD8+/TCRαβ+), natural killer (NK) cells (CD3-/CD16+/CD56+), and TCRδγ-positive (Tδγ) cells were determined by flow cytometry. 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 using available diagnostic kits. Results: L-theanine supplementation contributed to a significant decrease in IL-10 concentration after exercise, which resulted in higher IL-2 to IL-10 and IFN-γ to IL-10 ratios. In addition, a significant decrease after recovery in the number of CTLs, Treg to NK ratios, and Treg to CTL ratios was observed in the supplemented group. Conclusion: Despite a decrease in the number of certain cytotoxic cells (CTLs) and an increase in the proportion of Tregs relative to CTLs, LTE supplementation appears to have a beneficial effect on a disrupted Th1/Th2 balance in elite athletes, as evidenced by the decrease in IL-10 concentration.

Green tea contributes to good oral hygiene and fights bad breath.

March 2009 - Kushiyama et al. Relationship Between Intake of Green Tea and Periodontal Disease. Journal of Periodontology, 2009; 80 (3): 372 DOI: 10.1902/jop.2009.080510

Researchers have determined that drinking green tea daily promotes healthy teeth and gums. Background: Green tea is a very popular beverage, and in vitro studies have shown that green tea polyphenols inhibit the growth and cell adhesion of periodontal pathogens and their production of virulence factors. "We studied the epidemiological relationship between green tea consumption and periodontal disease." Methods: "We analyzed 940 Japanese men aged 49 to 59 years as part of a comprehensive health examination. Pocket depth (PD), clinical attachment loss (AL), and bleeding on probing (BOP) were used as periodontal parameters. We examined the relationship between green tea consumption and periodontal parameters. Green tea consumption was defined as the number of cups per day in a self-administered questionnaire." Results: Green tea consumption was inversely correlated with mean TD, mean CLP, and BOP. In multivariate linear regression models, each increase of one cup/day in green tea consumption was associated with a decrease of 0.023 mm in mean TD (P < 0.05), a decrease of 0.028 mm in mean AL (P < 0.05), and a decrease of 0.63% in BOP (P < 0.05), after adjusting for other confounding variables. Conclusion: There was a modest inverse association between green tea consumption and periodontal disease.

November 2010 - Xu X, Zhou XD, Wu CD. Tea Catechin EGCG Suppresses the mgl Gene Associated with Halitosis. Journal of Dental Research. 2010;89(11):1304-1308. doi:10.1177/0022034510378682

EGCG (epigallocatechin gallate) fights oral pathogens that cause bad breath, according to an article published in the Journal of Dental Health. It has been reported that epigallocatechin gallate (EGCg), the main antimicrobial catechin in tea, inhibits the growth and virulence factors of oral pathogens in vitro. Although the mechanism is unclear, the potential of EGCG in reducing halitosis caused by volatile sulfur compounds (VSCs) has been suggested. This study tested the hypothesis that EGCG reduces VSCs by deleting mgl, the gene encoding L-methionine-α-deamino-γ-mercaptomethane-lyase, responsible for the production of methyl mercaptan (CH3SH) by oral anaerobes. In this study, the effect of EGCG on in vitro growth, CH3SH production, and mgl gene expression in P. gingivalis W83 was investigated. EGCG inhibited the growth of P. gingivalis W83 (MIC = 97.5 µg/mL) and was bactericidal (MBC = 187.5 µg/mL). At levels below the MIC, EGCG inhibited CH3SH production and mgl mRNA and protein expression (p < 0.05). We conclude that EGCG may represent a natural and alternative agent to currently available antimicrobial products for the control of halitosis.

Green tea helps maintain a high level of alertness.

June 1999 - Lekh Raj Juneja, Djong-Chi Chu, Tsutomu Okubo, Yukiko Nagato, Hidehiko Yokogoshi. L-theanine—a unique amino acid of green tea and its relaxation effect in humans. Trends in Food Science & Technology, Volume 10, Issues 6–7, 1999, Pages 199-204, ISSN 0924-2244, https://doi.org/10.1016/S0924-2244(99)00044-8. (https://www.sciencedirect.com/science/article/pii/S0924224499000448)

L-theanine has a relaxing effect without causing drowsiness. Since ancient times, drinking green tea has been said to promote relaxation. The substance responsible for this relaxation sensation is theanine. Theanine is a unique amino acid found almost exclusively in tea plants and is the main component responsible for the exotic taste of "green" tea. It has been found that L-theanine administered intraperitoneally to rats reaches the brain within 30 minutes without any metabolic changes. Theanine also acts as a neurotransmitter in the brain and significantly lowers blood pressure in hypertensive rats. In general, animals always generate very weak electrical impulses on the surface of the brain, called brain waves. Brain waves are classified into four types, namely α, β, δ, and θ waves, depending on mental conditions. The generation of α waves is considered an indication of relaxation. In human volunteers, α waves were generated in the occipital and parietal regions of the brain surface within 40 minutes of oral administration of theanine (50 to 200 mg), indicating relaxation without causing drowsiness. "With the success of industrial production of L-theanine, we are now able to supply Suntheanine™ (the trade name for L-theanine), which offers a tremendous opportunity to develop foods and medical foods targeting relaxation and stress reduction. Taiyo Kagaku Co., Ltd, Japan, won the 1998 Food Ingredient Research Award for the development of Suntheanine™ at Food Ingredients in Europe (Frankfurt). The judges considered it to be "particularly well-documented and fascinating research."

The importance of storing matcha green tea properly

June 2002 - Haraguchi, Y. (Ito-En Co. Ltd., Sagara, Shizuoka (Japan). Central Research Inst.); Sano, H.; Nakazato, K.; Tomaru, K.; et al. Effects of storage conditions on quality of matcha [powdered tea] [2002] https://agris.fao.org/agris-search/search.do?recordID=JP2002005748

The best temperature for storing your matcha is between -70°C and 4°C: in other words, close the tin tightly and place your matcha in the refrigerator or freezer for optimal long-term storage. Storage at room temperature is also possible for a period not exceeding 6 months. The effects of different storage conditions (temperature and duration) on the quality of matcha were studied by measuring the chlorophyll and its derivatives, total vitamin C, surface colour value, and the quantity of oxygen in the tea pouch. A sensory test was also carried out at the same time. As a result, it was found that storing matcha at low temperatures (-70 and 4°C) maintained its quality in good condition for 24 weeks. In addition, storage at room temperature (25°C) maintained quality in moderate condition for 24 weeks. However, at the higher temperature of 37°C, the quality of matcha tea was found to be quite poor within 3 or 4 weeks. The cause of the changes in quality must be related to the decrease in the quantity of oxygen in the tea pouch at higher storage temperatures.

Green tea counteracts damage caused by oxidative stress.

September 2003 - David J. Weiss, Christopher R. Anderton. Determination of catechins in matcha green tea by micellar electrokinetic chromatography. Journal of Chromatography A, Volume 1011, Issues 1–2, 2003, Pages 173-180, ISSN 0021-9673, https://doi.org/10.1016/S0021-9673 (03)01133-6. (https://www.sciencedirect.com/science/article/pii/S0021967303011336)

Matcha tea contains 137 times more EGCG (epigallocatechin gallate) than regular green tea. EGCG is the main antioxidant found in matcha tea. The catechins in green tea are known to have many beneficial health properties. Recently, it has been suggested that matcha has greater potential health benefits than other green teas. Matcha is a special powdered green tea used in Japanese tea ceremonies. However, no investigation has been conducted to quantify the catechin content of matcha compared to common green teas. "We developed a rapid method for analyzing five catechins and caffeine in matcha using micellar electrokinetic chromatography." The results are presented for water and methanol extractions of matcha compared to the water extraction of a popular green tea. Using a comparison of mg of catechin/g of dry leaves, the results indicate that the concentration of epigallocatechin gallate (EGCG) available when drinking matcha tea is 137 times higher than the available quantity of EGCG in China Green Tips green tea, and at least three times higher than the highest value in the literature for other green teas.

January 2007 - Kenta Kimura, Makoto Ozeki, Lekh Raj Juneja, Hideki Ohira. L-Theanine reduces psychological and physiological stress responses. Biological Psychology, Volume 74, Issue 1, 2007, Pages 39-45. ISSN 0301-0511, https://doi.org/10.1016/j.biopsycho.2006.06.006. (https://www.sciencedirect.com/science/item/pii/S0301051106001451)

L-Theanine has proven anti-stress effects. L-theanine is an amino acid found in green tea leaves that is known to block the binding of l-glutamic acid to glutamate receptors in the brain. Given that the features of L-theanine suggest that it may influence psychological and physiological states under stress, the present study examined these possible effects in the laboratory using a mental arithmetic task as an acute stressor. Twelve participants underwent four separate trials: one in which they took L-theanine at the beginning of an experimental procedure, one in which they took L-theanine halfway through, and two control trials in which they took a placebo or nothing. The experimental sessions were realised in a double-blind manner, and their order was counterbalanced. The results showed that L-theanine intake led to a reduction in heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress task compared to the placebo control condition. Furthermore, 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 oral intake of L-theanine may exert anti-stress effects via inhibition of cortical neuron excitation.

Green tea helps reduce inflammation caused by UV rays.

September 2013 - Rhodes LE, Darby G, Massey KA, Clarke KA, Dew TP, Farrar MD, Bennett S, Watson RE, Williamson G, Nicolaou A. Oral green tea catechin metabolites are incorporated into human skin and protect against UV radiation-induced cutaneous inflammation in association with reduced production of pro-inflammatory eicosanoid 12-hydroxyeicosatetraenoic acid. Br J Nutr. 2013 Sep 14;110(5):891-900. doi: 10.1017/S0007114512006071. Epub 2013 Jan 28. PMID: 23351338.

Matcha tea reduces inflammation and helps repair UV-damaged skin. Green tea catechins (GTC) reduce UVR-induced inflammation in experimental models, but human studies are scarce and their skin bioavailability and photoprotection mechanism are unknown. We aimed to examine the oral skin absorption of GTC, its ability to protect human skin from erythema induced by a range of UVR doses, and its impact on the potent mediators of UVR inflammation produced by cyclooxygenase and lipoxygenase, PGE2 and 12-hydroxyeicosatetraenoic acid (12-HETE), respectively. In an open-label oral intervention study, sixteen healthy human subjects (phototype I/II) received low-dose GTC (540 mg) with vitamin C (50 mg) daily for 12 weeks. Before and after supplementation, skin from the buttock was exposed to UV radiation and the resulting erythema was quantified. Skin blister fluid and biopsies were collected from unexposed and UV-exposed skin 24 hours after provocation with pro-inflammatory ultraviolet radiation (three minimal erythema doses). Urine, skin tissue, and fluids were analyzed for catechin content, and skin fluid was analyzed for PGE2 and 12-HETE by liquid chromatography coupled with tandem MS. A total of fourteen subjects who completed the study complied with the supplement (twelve women, median age 42.5 years, range 29 to 59 years). Benzoic acid levels increased in skin fluid after supplementation (P = 0.03), and methylated gallic acid and several intact catechins and hydroxyphenylvalerolactones were detected in skin tissues and fluids. ASC analysis for UVR erythema revealed a reduced post-GTC response (P = 0.037). Pre-supplementation, PGE2, and 12-HETE were induced by UVR (P = 0.003, 0.0001). After GTC, UVR-induced 12-HETE decreased from a mean of 64 (sd 42) to 41 (sd 32) pg/μl (P = 0.01), while PGE2 was unchanged. Thus, GTC intake leads to the incorporation of catechin metabolites into human skin associated with abrogated UVR-induced 12-HETE; this may contribute to protection against inflammation caused by sunburn and potentially longer-term UV-induced damage.

Matcha and medical research

Green tea helps fight neurodegenerative diseases (Alzheimer's, etc.) and improve mental health.

June 2011 - Dragicevic N, Smith A, Lin X, Yuan F, Copes N, Delic V, Tan J, Cao C, Shytle RD, Bradshaw PC. Green tea EGCG and other flavonoids reduce Alzheimer's amyloid-induced mitochondrial dysfunction. J Alzheimers Dis. 2011;26(3):507-21. doi: 10.3233/JAD-2011-101629. PMID: 21694462.

Study results reveal that green tea reduces the impact of these substances on cells in the nervous system. Mitochondrial dysfunction induced by amyloid β (Aβ) may play a role in the onset and progression of Alzheimer's disease (AD). Therefore, targeted therapies to improve mitochondrial function could be beneficial. Plant-derived flavonoids have shown promise in improving certain AD phenotypes, but the overall mechanism(s) of action by which flavonoids protect against AD is still unknown. To identify flavonoids and other natural products that may correct amyloid-induced mitochondrial dysfunction, 25 natural products were selected for their ability to restore altered mitochondrial membrane potential (MMP), reactive oxygen species (ROS) production, or ATP levels in neuroblastoma cells expressing a mutant precursor of amyloid-β protein (AβPP). Epigallocatechin-3-gallate (EGCG) and luteolin were identified as the two main mitochondrial restoration compounds from in vitro screening. EGCG was further tested in vivo to determine its effects on brain mitochondrial function in a transgenic mouse model of AD with dual AβPP/PS-1 (presenilin 1) mutations. EGCG treatment restored mitochondrial respiratory rates, MMP, ROS production, and ATP levels by 50–85% in isolated mitochondria from the hippocampus, cortex, and striatum. The results of this study further confirm the notion that EGCG and other flavonoids, such as luteolin, are "multipotent therapeutic agents" that not only reduce toxic levels of brain Aβ, but also hold the potential to protect neuronal mitochondrial function in AD.

Green tea helps prevent certain diseases and long-term conditions (cancer, etc.).

May 2001 - Veronica Wendy Setiawan, Zuo‐Feng Zhang, Guo‐Pei Yu, Qing‐Yi Lu, Yong‐Liang Li, Ming‐Lan Lu, Ming‐Rong Wang, Chun Hua Guo, Shun‐Zhang Yu, Robert C. Kurtz, Chung‐Cheng Hsieh. Protective effect of green tea on the risks of chronic gastritis and stomach cancer. First published: April 9, 2001. https://doi.org/10.1002/ijc.1231 (https://onlinelibrary.wiley.com/doi/full/10.1002/ijc.1231)

A press release on a study by the University of California, Los Angeles (UCLA) showed that green tea is effective in preventing chronic gastritis. Green tea drinkers suffer from chronic gastritis half as often as non-drinkers, according to a new study conducted by researchers at the UCLA School of Public Health and the Jonsson Comprehensive Cancer Center at UCLA. The results are the first to link green tea to lower rates of chronic gastritis. "Despite the downward trend, stomach cancer remains the second most common cancer worldwide. We examined the role of green tea consumption on the risks of chronic gastritis and stomach cancer. A population-based case-control study was conducted in Yangzhong, China, with 133 cases of stomach cancer, 166 cases of chronic gastritis, and 433 healthy controls. Epidemiological data were collected using a standard questionnaire, and odds ratios (OR) and 95% confidence intervals (CI) were estimated using logistic regression models in SAS. An inverse association was observed between green tea consumption and the risks of chronic gastritis and stomach cancer. After adjusting for age, sex, education level, body mass index, pack-years of smoking, and alcohol consumption, the ORs for green tea consumption were 0.52 (95% CI: 0.29-0.94) and 0.49 (95% CI: 0.31-0.77) for stomach cancer and chronic gastritis, respectively. In addition, dose-response relationships were observed with years of green tea consumption in both diseases. The results further confirm the protective effect of green tea against stomach cancer. This is the first time that green tea consumption has been shown to be protective against chronic gastritis, which may be important when designing intervention strategies for stomach cancer and its premalignant lesions in high-risk populations.

March 2007 - Guo Y, Zhi F, Chen P, et al. Green tea and the risk of prostate cancer: A systematic review and meta-analysis. Medicine (Baltimore). 2017;96(13):e6426. doi:10.1097/MD.0000000000006426

The catechin contained in matcha could help fight prostate cancer. "Prostate cancer (PCa) remains the second most frequently diagnosed cancer. In recent years, chemoprevention of PCa has become a possible concept. In particular, many foods rich in phytochemicals are suggested to reduce the risk of cancer. Among these foods, green tea is considered an effective prevention for various cancers. However, previous clinical trials and meta-analyses on the relationship between green tea consumption and PCa risk have produced inconsistent results. This study aims to determine the dose-response association of green tea consumption with PCa risk and the preventive effect of green tea catechins on PCa risk. Seven observational studies and three randomized controlled trials were extracted from the Cochrane Library, PubMed, ScienceDirect Online, and manual searches. STATA (version 12.0) was used to analyze the data. Relative risks (RR) and 95% confidence intervals were pooled using fixed-effect or random-effect modeling. Dose-response relationships were assessed with green tea consumption categories. Although there was no statistical significance in the comparison of the highest category versus the lowest category, there was a trend toward a reduced incidence of PCa with each increase of one cup/day of green tea (P = 0.08). Our dose-response meta-analysis further demonstrated that higher green tea consumption was linearly associated with a reduced risk of PCa with more than 7 cups/day. Furthermore, green tea catechins were effective in preventing PCa with an RR of 0.38 (P = 0.02). In conclusion, our dose-response meta-analysis evaluated the association of green tea consumption with PCa risk in a systematic and quantitative manner. This is the first meta-analysis of green tea catechin consumption and PCa incidence. Our new data demonstrated that higher green tea consumption linearly reduced the risk of PCa with more than 7 cups/day and that green tea catechins were effective in preventing PCa. However, further studies are needed to support these findings.

April 2009 - Noriko Yamabe, Ki Sung Kang, Jong Moon Hur, and Takako Yokozawa. Type 2 Diabetic OLETF Rats. Journal of Medicinal Food. Aug 2009.714-721. Published in Volume: 12 Issue 4: September 7, 2009. http://doi.org/10.1089/jmf.2008.1282

A study published in the Journal of Medicinal Food showed that matcha protects against liver and kidney damage thanks to its effects in reducing liver glucose, triglycerides, and total cholesterol levels, as well as its antioxidant properties. "Matcha, a powdered green tea produced by grinding with a stone mill, has been popularly used in traditional tea ceremonies and foods in Japan. Matcha green tea is well known to be richer in certain nutritional elements and epigallocatechin 3-O-gallate than other green teas. In our previous study, epigallocatechin 3-O-gallate showed protective effects against kidney damage in a rat model of diabetic nephropathy. In the present study, we investigated the preventive effects of matcha (50, 100, or 200 mg/kg/day) on the progression of liver and kidney damage in Otsuka Long-Evans Tokushima Fatty (OLETF) type 2 diabetic rats. OLETF rats were given matcha orally for 16 weeks, and we evaluated biochemical parameters in serum, liver, and kidney, and expression levels of major advanced glycation products (AGEs), Nɛ-(carboxymethyl)lysine (CML) and Nɛ-(carboxyethyl)lysine (CEL), AGE receptor (RAGE), and sterol regulatory element-binding proteins (SREBP)-1 and -2. Serum total protein levels were significantly increased by matcha administration, while serum albumin and glycosylated protein levels and renal glucose and triglyceride levels were only slightly or not at all affected. However, matcha treatment significantly lowered serum and liver glucose, triglyceride, and total cholesterol levels, renal AGE levels, and serum levels of thiobarbituric acid reactive substances. In addition, matcha supplementation resulted in decreased renal expressions of LMC, CEL, and RAGE, as well as increased hepatic expression of SREBP-2, but not SREBP-1. These results suggest that matcha protects against liver and kidney damage by suppressing renal AGE accumulation, decreasing hepatic glucose, triglyceride, and total cholesterol levels, and through its antioxidant activities.

May 2009 - Green Tea Extract Shows Promise In Leukemia Trials. Mayo Clinic. May 27, 2009. https://newsnetwork.mayoclinic.org/discussion/green-tea-extract-appears-to-keep-cancer-in-check-in-majority-of-cll-patients/

A green tea extract appears to have clinical activity with low toxicity in patients with chronic lymphocytic leukemia (CLL) who used it in a phase II clinical trial, according to researchers at the Mayo Clinic. "The results, which will be presented on Monday, June 7, at the American Society of Clinical Oncology (ASCO) annual meeting, are the latest in a series of Mayo studies to show promise for the use of the chemical epigallocatechin gallate (EGCG)—the major component of green tea—in reducing the number of leukemia cells in patients with CLL. Mayo first tested EGCG in various laboratory tests about eight years ago, and it was found to reduce the survival of CLL leukemia cells. This laboratory discovery was followed by a successful Phase I clinical trial—the first time green tea extract has been studied in patients with CLL."

Matcha green tea helps prevent type 2 diabetes and improve diabetes treatment.

February 2012 - Ortsäter, H., Grankvist, N., Wolfram, S. et al. Diet supplementation with green tea extract epigallocatechin gallate prevents progression to glucose intolerance in db/db mice. Nutr Metab (Lond) 9, 11 (2012). https://doi.org/10.1186/1743-7075-9-11

EGCG (epigallocatechin gallate) contained in green tea and concentrated in matcha tea improves glucose tolerance in diabetic mice. Researchers concluded that a diet supplemented with EGCG would be effective in preventing and treating type 2 diabetes. Background: Green tea was suggested as a therapeutic agent for treating diabetes more than 70 years ago, but the mechanisms behind its antidiabetic effect remain elusive. In this study, we addressed this issue by feeding a green tea extract (TEAVIGO™) with a high content of epigallocatechin gallate (EGCG) or the thiazolidinedione PPAR-γ agonist rosiglitazone, as a positive control, to db/db mice, an animal model for diabetes. Methods: Young db/db mice (7 weeks old) were randomized and assigned to receive diets supplemented with or without EGCG or rosiglitazone for 10 weeks. Fasting blood glucose, weight, and food intake were measured throughout the treatment period. Glucose and insulin levels were determined during an oral glucose tolerance test after 10 weeks of treatment. Pancreata were collected at the end of the study for blinded histomorphometric analysis. Islets were isolated and their mRNA expression analyzed by quantitative RT-PCR. Results: The results show that, in db/db mice, EGCG improves glucose tolerance and increases glucose-stimulating insulin secretion. EGCG supplementation reduces the number of pathologically altered islets of Langerhans, increases the number and size of islets, and increases the pancreatic endocrine area. These effects occurred in parallel with a reduction in markers of endoplasmic reticulum stress in the islets, likely related to the antioxidant capacity of EGCG. Conclusions: This study shows that green tea extract EGCG significantly preserves islet structure and improves glucose tolerance in genetically diabetic mice. Dietary supplementation with EGCG could potentially contribute to nutritional strategies for the prevention and treatment of type 2 diabetes.

Matcha green tea powder affects substrate oxidation during moderate-intensity exercise in women

September 2020 - Mark E. T. Willems, Hillary L. Fry, Majeedah A. Belding & Mojtaba Kaviani (2020) Three Weeks Daily Intake of Matcha Green Tea Powder Affects Substrate Oxidation during Moderate-Intensity Exercise in Females, Journal of Dietary Supplements, DOI: 10.1080/19390211.2020.1811443

"Artificial green tea extracts can improve exercise-induced fat oxidation. Consuming natural matcha green tea involves ingesting powdered green tea leaves. We examined the effects of three weeks of daily consumption of matcha powder on substrate oxidation during moderate-intensity exercise in women. Women with regular menstrual cycles (n = 12, age: 28 ± 10 years, body mass: 69 ± 17 kg, size: 163 ± 6 cm) volunteered to perform a progressive walking test to determine the individual moderate exercise intensity (four equivalent) for the next 30-minute walk on the treadmill. The study had a randomized, placebo-controlled crossover design with participants tested between days 9 and 11 of the menstrual cycle (follicular phase). Participants consumed 3 x 1 gram capsules of superior quality matcha (OMGTea Ltd, UK) daily for three weeks, with the final dose (1 gram) taken two hours before the 30-minute walk (walking speed: 5.8 ± 0.4 km/h). Matcha had no effect on physiological responses (e.g., heart rate, placebo: 127 ± 14; Matcha: 124 ± 14 beats · min^(−1), p = 0.154), but resulted in a decrease in respiratory exchange ratio (placebo: 0.872 ± 0.040; Matcha: 0.839 ± 0.035) (p = 0.033), higher fat oxidation of 35 ± 47% (placebo: 0.21 ± 0.08; Matcha: 0.26 ± 0.06 g · min^(−1) (p = 0.034) and lower carbohydrate oxidation (placebo: 0.75 ± 0.21; matcha: 0.60 ± 0.18 g · min^(−1) (p = 0.048) during 30 min of moderate-intensity walking. Energy expenditure was similar for both conditions. There was no significant correlation between body fat percentage and the absolute or relative change in fat oxidation induced by matcha during exercise. Continuous consumption of matcha green tea affects exercise-induced metabolic responses by increasing fat oxidation during moderate-intensity exercise in adult women, apparently independent of body composition.

Green tea consumption and colorectal cancer risk in Japan: the Takayama study

June 2019 - Keiko Wada, Shino Oba, Michiko Tsuji, Yuko Goto, Fumi Mizuta, Sachi Koda, Takahiro Uji, Akihiro Hori, Shinobu Tanabashi, Shogen Matsushita, Naoki Tokimitsu, Chisato Nagata, Green tea intake and colorectal cancer risk in Japan: the Takayama study, Japanese Journal of Clinical Oncology, Volume 49, Issue 6, June 2019, Pages 515–520, https://doi.org/10.1093/jjco/hyz030

Green tea consumption and colorectal cancer risk in Japan: the Takayama study. Background: Green tea has been shown to have a preventive effect against colorectal cancer in animal models. However, the results of epidemiological studies on the association between green tea consumption and colorectal cancer have been inconsistent. We aimed to evaluate the risk of colorectal cancer in relation to green tea consumption in a prospective population-based cohort study. Methods: The subjects were 13,957 men and 16,374 women aged 35 years or older in September 1992. Participants' green tea consumption was obtained by administering a food frequency questionnaire. The incidence of colorectal cancer was confirmed by population-based regional cancer registries and by histological identification through colonoscopy at two major hospitals in the study area. Colorectal cancer was defined as the sum of code C18 (colon cancer) and codes C19 and C20 (rectal cancer) according to ICD-10. Results: By March 2008, 429 men and 343 women had been diagnosed with colorectal cancer. No significant association was found between green tea consumption and colorectal cancer in men and women, respectively. However, for men, compared to the "none or less than once a day" green tea consumption group, the multiple-adjusted relative risks (95% CI) for colon cancer were 1.32 (0.90, 1.94), 0.76, 1.02) and 0.78 (0.49, 1.22), respectively, in the "once a day," "2 to 3 times a day," and "four times a day or more" groups (trend P = 0.045). Conclusions: This study found no significant overall association between green tea consumption and the risk of colorectal cancer, except that there was a weak trend toward higher green tea consumption with a decreased risk of colon cancer in men.

Drinking green tea may reduce the risk of heart attacks.

April 2013 - Tian C, Huang Q, Yang L, et al. Green tea consumption is associated with reduced incident CHD and improved CHD-related biomarkers in the Dongfeng-Tongji cohort [published correction appears in Sci Rep. 2017 May 31;7:45949]. Sci Rep. 2016;6:24353. Published 2016 Apr 13. doi:10.1038/srep24353

Chinese researchers show that drinking green tea can reduce the risk of heart attacks. Prospective studies on the association of green tea with the incidence risk of coronary heart disease (CHD) were rare. This study examined whether green tea can reduce the incidence of coronary heart disease and have a beneficial effect on risk markers related to coronary heart disease in the middle-aged and older Chinese population. We included 19,471 participants who did not have coronary heart disease, stroke, or cancer at baseline from September 2008 to June 2010 and were followed up until October 2013. Cox proportional hazards models were used to examine the hazard ratios (HR) of coronary heart disease incidence in relation to green tea consumption. Linear regression models were used to assess the effect of green tea on 5-year changes in biomarkers related to coronary heart disease. Compared with non-green tea drinkers, the multivariate-adjusted HR for coronary heart disease was 0.89 (95% CI, 0.81-0.98) among green tea drinkers. In particular, the reduction in the incidence risk of coronary heart disease with green tea consumption was more evident in male participants, those over 60 years of age, those who were overweight, or those with diabetes mellitus. In addition, green tea consumption improved several risk markers related to coronary heart disease, including total cholesterol, HDL cholesterol, triglycerides, mean platelet volume, and uric acid. In conclusion, green tea consumption was associated with a reduced risk of coronary heart disease incidence in middle-aged and older Chinese populations, and the association may be partly due to changes in biomarkers related to coronary heart disease.

November 2013 - Lenore Arab, Weiqing Liu, and David Elashoff. Green and Black Tea Consumption and Risk of Stroke. Originally published February 19, 2009,https://doi.org/10.1161/STROKEAHA.108.538470Stroke 2009;40:1786–1792, https://www.ahajournals.org/doi/full/10.1161/strokeaha.108.538470

A study published by the AHA Journal concluded that green tea has a significant influence on reducing cardiovascular risk factors such as insulin resistance, blood pressure, and inflammation. Background and objective: Experimental stroke models provide consistent evidence of smaller stroke volumes in animals ingesting tea components or tea extracts. To assess whether a similar association of black or green tea consumption with reduced risk is evident in human populations, we sought to identify and summarize all human clinical and observational data on tea and stroke. Methods: We searched PubMed and Web of Science for all studies on stroke and tea consumption in humans with original data, including estimation or measurement of tea consumption and results of fatal or non-fatal stroke. Data from 9 studies involving 4,378 strokes among 194,965 individuals were pooled. The primary result was the occurrence of fatal or non-fatal stroke. We tested for heterogeneity and calculated the summary effect estimate associated with consuming ≥3 cups of tea (green tea or black tea) per day using random-effects and fixed-effects models for homogeneous studies. Publication bias was also assessed. Results: Regardless of country of origin, individuals consuming ≥3 cups of tea per day had a 21% lower risk of stroke than those consuming <1 cup per day (absolute risk reduction, 0.79; CI, 0.73 to 0.85). The proportion of heterogeneity not explained by chance alone was 23.8%. Conclusions: Although a randomized clinical trial is needed to confirm the effect, this meta-analysis suggests that daily consumption of green tea or black tea equivalent to 3 cups per day may prevent the onset of ischemic stroke.

Green tea helps prevent glaucoma and promotes eye health.

January 2010 - Kai On Chu, Kwok Ping Chan, Chi Chiu Wang‡, Ching Yan Chu‡, Wai Ying Li†, Kwong Wai Choy, Michael Scott Rogers, and Chi Pui Pang. Green Tea Catechins and Their Oxidative Protection in the Rat Eye. J. Agric. Food Chem. 2010, 58, 3, 1523–1534. https://pubs.acs.org/doi/full/10.1021/jf9032602

According to a study published in the Journal of Agricultural and Food Chemistry, catechins (EGCG) can penetrate eye tissue and protect against glaucoma and other eye diseases. Catechins, the active constituents of green tea, are well-known natural antioxidants. It has been suggested that consumption of green tea extract (GTE) may be beneficial to the eye, and the pharmacokinetics of catechins and oxidation status in the rat eye were studied after oral administration. Sprague-Dawley rats (a laboratory rat strain) were fed GTE and sacrificed at different time intervals. Their eyes were dissected into cornea, lens, retina, choroid-sclera, vitreous humor, and aqueous humor for analysis of catechins and 8-epi-isoprostane by HPLC-ECD and GC-NCI-MS, respectively. Catechins were differentially distributed in ocular tissues. Gallocatechin was present at the highest concentration in the retina, 22729.4 ± 4229.4 pmol/g, and epigallocatechin in the aqueous humor at 602.9 ± 116.7 nM. The corresponding area under the curve was 207,000 pmol × h/g and 2035.0 ± 531.7 nM × h, respectively. The time to maximum concentration of catechins ranged from 0.5 to 12.2 h. Significant reductions in 8-epi-isoprostane levels were observed in all compartments except the choroid-sclera or plasma, indicating antioxidant activities of catechins in these tissues.

EGCG, a compound found in green tea, can be used as an adjunctive treatment in HIV-1 infection.

December 2006 - Mike P. Williamson, Theron G. McCormick, Christina L. Nance, William T. Shearer. Epigallocatechin gallate, the main polyphenol in green tea, binds to the T-cell receptor, CD4: Potential for HIV-1 therapy. Journal of Allergy and Clinical Immunology, Volume 118, Issue 6, 2006, Pages 1369-1374, ISSN 0091-6749, https://doi.org/10.1016/j.jaci.2006.08.016. (https://www.sciencedirect.com/science/article/pii/S0091674906017635).

This study showed that EGCG (Epigallocatechin gallate) have an anti-HIV-1 effect because they prevent HIV-1 glycoprotein cells from binding to T cells. This effect of EGCG shows promise for future treatments. Background: It has been proposed that the green tea flavonoid EGCG has an anti-HIV-1 effect by preventing the binding of HIV-1 glycoprotein (gp) 120 to the CD4 molecule on T cells. Objective: To demonstrate that EGCG binds to the CD4 molecule at the gp120 binding site and inhibits gp120 binding at physiologically relevant levels, thereby establishing EGCG as a potential therapeutic treatment for HIV-1 infection. Methods: Nuclear magnetic resonance spectroscopy was used to examine the binding of EGCG and the control, (-) - catechin, to CD4-IgG2 (PRO 542®). The binding of Gp120 to human CD4+ T cells was analysed by flow cytometry. Results: The addition of CD4 to EGCG produced a linear decrease in the nuclear magnetic resonance signal intensity of EGCG but not the control, (-) - catechin. In saturation transfer difference experiments, the addition of 5.8 μmol/ L CD4 to 310 μmol/L EGCG produced strong saturation at the aromatic rings of EGCG, but identical concentrations of (-) - catechin produced much weaker effects, implying that EGCG/CD4 binding is strong enough to significantly reduce gp120/CD4 binding. Molecular modeling studies suggested a binding site for EGCG in the D1 domain of CD4, the pocket that binds gp120. Physiologically relevant concentrations of EGCG (0.2 μmol/L) inhibited the binding of gp120 to isolated human CD4+ T cells. Conclusion: "We have demonstrated clear evidence of high-affinity binding of EGCG to the CD4 molecule with a Kd of approximately 10 nmol/L and inhibition of gp120 binding to human CD4+ T cells." Clinical implications: Epigallocatechin gallate may be used as an adjunctive therapy in HIV-1 infection.

Green tea extract or matcha? My personal review as an insider and matcha lover.

By Valentin from Kumiko Matcha

Many studies have sought to analyze green tea in general using green tea extract, rather than simple green tea pouches. This is a green tea concentrate obtained through a chemical process that involves infusing tea leaves in an alcohol solution and then reducing this solution to a solid powder. Matcha tea is similar to green tea extract in several ways, in that it is a green tea concentrate. However, the difference is that it comes from tea leaves that have been processed and ground naturally using a traditional method. Therefore, it may seem logical to think that the results of studies that used green tea extract are even more relevant and accurate for matcha than for simple green tea pouches. In addition, at Kumiko Matcha, our matcha tea is premium grade and certified organic. Nevertheless, as I am not a scientist myself, I believe it is essential and wise to verify the accuracy of the statements and health claims made in various studies (which can sometimes contradict each other as research progresses). For now, it seems that matcha is recognised for its virtues by numerous research results, confirming the ability of this green tea powder to be an ally for wellbeing, in addition to being delicious!

Editorial committee: Valentin Van Nhut, Jimmy Braun.