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.
Highlights
Theanine is an L-glutamate analogue and a non-protein amino acid that is particular to the tea plant (Camellia sinensis (L.) Kuntze) [1]
We focused on the contents of theanine, arginine, caffeine, and epigallocatechin gallate (EGCG)
The relationship between the amount of matcha intake and suppression of adrenal hypertrophy was examined using matcha sample no. 1, whose theanine content represented the median of seven samples
Summary
Theanine is an L-glutamate analogue and a non-protein amino acid that is particular to the tea plant (Camellia sinensis (L.) Kuntze) [1]. The amount of theanine, which is the most abundant amino acid in green tea leaves, depends on nitrogen supply absorbed from the roots [2]. Matcha is a fine-powdered green tea that is prepared from tea leaves protected from sunlight. When tea leaves are protected from direct sunlight, their amino acid content, especially theanine, remains high because the hydration of theanine used in the biosynthesis of catechin is lowered [3,4]. Cultivation under shade for about three weeks is necessary before harvest [5]. Given their protection from sunlight, catechin content is lower in matcha than in other popular green teas prepared from leaves grown in sunlight [3,6]. Matcha has a high content of caffeine because the buds and young leaves of Nutrients 2018, 10, 1468; doi:10.3390/nu10101468 www.mdpi.com/journal/nutrients
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