An amino acid found naturally in green tea, theanine is said to promote relaxation and treat a number of mental health problems. For instance, many people take theanine supplements to alleviate anxiety, fight depression, and reduce stress. So far, scientists have yet to extensively explore the health effects of theanine. However, preliminary research suggests that theanine may help lift mood, enhance brain function, and calm the body's response to stress. While it's too soon to recommend the use of theanine supplements for treatment or prevention of any health condition, upping your theanine intake by drinking green tea may offer a wide range of health benefits. In fact, studies show that people who drink green tea on a regular basis may have increased protection against high blood pressure and high cholesterol (two top risk factors for heart disease), as well as some forms of cancer.