Tomatoes. Although their peak season (June to August) is here, tomatoes should be eaten year-round. "They don't need to be fresh," Willett says. "That's important because they are very expensive in winter. Having a little bit of pasta sauce will actually be better for you." That's because there is a higher concentration of the antioxidant lycopene—protective against prostate and colorectal cancers—in a cooked tomato than in a raw one because the heat breaks down more cell walls of the tomato than our teeth can. But that doesn't mean you should shy away from fresh tomatoes, McKindley says. "We need to have a blend of raw and cooked because the cooking process will degrade other nutrients that are heat-sensitive like vitamin C and the B vitamins."
The American Institute for Cancer Research regularly updates its list of antioxidant foods and the research behind them.