Green tea has been studied for its antioxidants and weight loss properties, but recent news has indicated that the beverage may even improve depressive symptoms. A study at the Tohoku University Graduate School in Sendai in Tokyo shows that drinking several cups during the day may act as a mood booster, particularly for those who are above 70 years of age. Green tea wasn't the only beverage studied, however. Other caffeinated beverages like black and oolong teas and coffee were involved, but none had the same mood improving effects, which, although from the same sinensis plant, is processed differently to preserve antioxidants.
This study involved 1058 participants, both males and females at 70 years of age and older. 34 to 40 percent of those studied suffered from depressive symptoms, and about a quarter had severe depression. During the study, these participants drank four or more cups of green tea per day, and, by the end, 44 percent of the total participants were seen to have less depressive symptoms.
How does this work? The researchers at Tohoku University Graduate School think that the improvement in mood is the result of an amino acid in green tea, theanine, which isn't present in any of the other caffeinated beverages studied. Theanine is said to have a tranquilizing effect in the brain, which results from the production of alpha brain waves that induce a state of relaxation. Additionally, theanine alters the levels of neurotransmitters like serotonin and dopamine, both of which are often the target of antidepressant medications used to elevate moods in patients.