Resveratrol, a chemical found in red grapes, is more effective in smaller doses at preventing bowel cancer in mice than high doses, according to new research. Previous research looked at high doses of purified resveratrol to study its potential to prevent cancer. This is the first study to look at the effects of a lower daily dose — equivalent to the amount of resveratrol found in one large (approx. 250ml) glass of red wine — comparing it with a dose 200 times higher.