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Lee Swanson Research Update
Feeling Stressed? Pour a Cup of Green Tea
October 2009
A Japanese study has found that drinking five cups of green tea per day may reduce the incidence of psychological distress by 20%. That’s important because according to World Health Organization estimates, more than 450 million people worldwide suffer from stress.
In a study with 42,093 Japanese individuals, 2,774 people—6.6% of the study population—suffered from psychological stress and green tea consumption was said to improve psychological well-being.
Researchers led by Atsushi Hozawa from the Tohoku University Graduate School of Medicine reported their findings in the American Journal of Clinical Nutrition.
Green tea and its extracts already have a positive reputation, with studies reporting they may offer protective effects against Alzheimer’s and certain cancers, improve cardiovascular and oral health, and play a positive role in weight management.
Despite reports already stating that green tea or its constituents might reduce psychological stress, no large-scale study has evaluated the relationship between green tea consumption and psychological distress, the researchers said.
After adjusting results for potential confounding factors, a significant inverse association between green tea consumption and psychological distress was observed for people who drank at least five cups of green tea per day, compared to those who drank less than one cup per day.
Being an epidemiological study, the authors could not offer any evidence as to what the active constituents behind the apparent benefits could be. Further study is needed to elucidate the bioactives and mechanism of action. The four primary polyphenols found in fresh tea leaves are epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin (EC).
A previous Japanese study reported that green tea extracts may offset the signs of physical and mental fatigue associated with modern stressful lives. Five days of supplementation with EGCG was found to reduce levels of oxidized species related to fatigue in an animal model, according to findings published in the journal Nutrition.
American Journal of Clinical Nutrition Published online ahead of print.
