A potent antioxidant, green tea has been found in studies to boost longevity and the immune system, cut risk of heart disease and reduce inflammation. Antibacterial and antiviral, it also helps stimulate the burning of calories according to researchers at the University of Geneva. Drinking more than two cups a day keeps mind and memory sharp with age. Japanese women who drink green tea also have lower risk of breast cancer and better outcomes if they do contract the disease. Aim for three to six cups a day.