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Randomized Controlled Trial
. 2018 Oct 10;10(10):1468.
doi: 10.3390/nu10101468.

Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials

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Free PMC article
Randomized Controlled Trial

Stress-Reducing Function of Matcha Green Tea in Animal Experiments and Clinical Trials

Keiko Unno et al. Nutrients. .
Free PMC article

Abstract

Theanine, a major amino acid in green tea, exhibits a stress-reducing effect in mice and humans. Matcha, which is essentially theanine-rich powdered green tea, is abundant in caffeine. Caffeine has a strong antagonistic effect against theanine. The stress-reducing effect of matcha was examined with an animal experiment and a clinical trial. The stress-reducing effect of matcha marketed in Japan and abroad was assessed based on its composition. The stress-reducing effect of matcha in mice was evaluated as suppressed adrenal hypertrophy using territorially-based loaded stress. High contents of theanine and arginine in matcha exhibited a high stress-reducing effect. However, an effective stress-reducing outcome was only possible when the molar ratio of caffeine and epigallocatechin gallate (EGCG) to theanine and arginine was less than two. Participants (n = 39) consumed test-matcha, which was expected to have a stress-reducing effect, or placebo-matcha, where no effect was expected. Anxiety, a reaction to stress, was significantly lower in the test-matcha group than in the placebo group. To predict mental function of each matcha, both the quantity of theanine and the ratios of caffeine, EGCG, and arginine against theanine need to be verified.

Keywords: adrenal hypertrophy; anxiety; caffeine; catechin; green tea; matcha; salivary α-amylase activity; stress-reduction; theanine.

Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Scheme 1
Scheme 1
Study design of the animal experiment.
Figure 1
Figure 1
Suppression of adrenal hypertrophy by matcha intake in stressed mice. (a) Mice consumed a matcha sample (no. 1) in a powder diet for seven days (single rearing for six days and confrontational rearing for one day). Since each mouse (ca. 30 g) ingested about five grams of diet per day, the intake of matcha was set to 0, 10, 17, 33, and 100 mg/kg; (b) Mice were fed a diet containing matcha from no. 1 to no. 5 at a concentration of 33 mg/kg, and from no. 6 to no. 7 at a concentration of 50 mg/kg. Each bar shows the mean ± SEM (n = 4–8; * p < 0.05).
Figure 2
Figure 2
Correlations between adrenal hypertrophy and ingestion of matcha components in stressed mice. The amounts of (a) theanine and (b) caffeine were calculated from the matcha-containing feed that each mouse consumed, as shown in Table 3. Each point and bar shows the mean ± SEM (n = 4–8).
Figure 3
Figure 3
Interaction of tea components on adrenal hypertrophy in stressed mice. Mice consumed powder diet containing theanine, caffeine, EGCG, and Arg for seven days (single rearing for six days and confrontational rearing for one day). Control mice were fed a powder diet, CE-2. The concentration of theanine was 0.32 mg/kg. Mice ingested feed that contained each component as molar ratios of matcha sample no. 6, i.e., the molar ratio of theanine:caffeine:EGCG:Arg was 1:2:1:0.7. Each bar shows the mean ± SEM (n = 4; * p < 0.05).
Figure 4
Figure 4
Effect of matcha ingestion on students during university and pharmacy practice. (a) The STAI test was administered before and on the eighth day of pharmacy practice. (b, left bars) The level of sAAm was measured in participants every morning for three days during routine daily life at the university before intake of matcha as the baseline. (b, middle and right bars) After the ingestion of matcha started, median sAAm of each participant for the last three days at the university and pharmacy practice was used for statistical analysis. The median of (c) sAAe and (d) subjective stress of each participant of the last three days at the university and pharmacy practice are shown. Each bar shows the mean ± SEM (test matcha, n = 19; placebo matcha, n = 20).
Figure 5
Figure 5
The amount of theanine and the molar ratio of caffeine and EGCG to theanine and Arg in (a) 76 samples of matcha marketed in Japan and (b) 67 samples of matcha marketed overseas. Based on data in humans, samples in the section, theanine > 17 mg/g, and molar ratio of caffeine and EGCG to theanine and Arg < 2 are expected to show a stress-reducing effect.
Figure 5
Figure 5
The amount of theanine and the molar ratio of caffeine and EGCG to theanine and Arg in (a) 76 samples of matcha marketed in Japan and (b) 67 samples of matcha marketed overseas. Based on data in humans, samples in the section, theanine > 17 mg/g, and molar ratio of caffeine and EGCG to theanine and Arg < 2 are expected to show a stress-reducing effect.

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