Can eating grapes and other antioxidant rich foods really decrease your risk of getting cancer?

Probably not: Studies of nutritional supplements have provided inconsistent results in cancer prevention. Some studies have actually shown increased risk of cancer in patients taking vitamin E or beta carotene. Because it is difficult to collect accurate food histories, it is hard to gauge the degree of protection from eating specific foods. Either way, the effect size is likely miniscule.

Not directly: Antioxidants help reduce inflammation and with cell repair, so a heathy diet and active lifestyle will help reduce your risk. But cancer is caused by multiple factors, so don't forget screening tests.