In tests on human intestinal cells, scientists discovered that adding vitamin C or table sugar (or a combination of the substances) to green tea increased the absorption of antioxidants by as much as three times. Also found in fruits, vegetables, and other foods, antioxidants help fight free radicals (chemical by-products known to damage DNA).
Past research suggests that drinking green tea may help prevent tooth erosion, periodontal disease, stroke, and cognitive impairment. However, studies on green's cancer-fighting properties have yielded mixed results. In a 2009 review of 51 studies on the link between green tea consumption and cancer, for instance, researchers found that the tea may decrease prostate cancer risk but might have limited benefits for liver cancer. There was also "limited moderate to strong evidence" for green tea's ability to help prevent lung, pancreatic, and colorectal cancer, and conflicting evidence for cancer of the esophagus.