Effects of theanine and other ingredients of tea on stress and aging.

Abstract

Abstract Stress is one of the most potent environmental factors known to accelerate brain aging. Suppression or prevention of stress-induced alterations is a potential therapeutic strategy for healthy aging. To clarify the mechanism of stress-induced brain aging, a new experimental animal model of psychosocial stress using male animal's territoriality has been developed. Theanine (γ-glutamylethylamide) is the most abundant amino acid in tea and an important sweet umami taste of green tea. Theanine intake suppressed stress-derived adrenal hypertrophy, which is a sensitive stress-responsive phenomenon. In chronically stressed aged mice, theanine intake suppressed stress-induced disadvantages such as shortened lifespan, cerebral atrophy, cognitive dysfunction, and depression. The anti-stress effect of theanine was observed not only in mice but also in humans. However, the anti-stress effect of theanine was blocked by two other main components of tea, caffeine and epigallocatechin gallate (EGCG). On the other hand, epigallocatechin (EGC) and arginine (Arg) cooperatively abolished the counter-effect of caffeine and EGCG on psychosocial stress in mice. These results suggest that drinking green tea exhibits anti-stress effects when the contents of theanine, EGC, and Arg are relatively high and those of caffeine and EGCG are low.