Brazil nuts, a holiday favorite, are the food richest in selenium, a potent antioxidant linked to low rates of cancer and heart disease. If you ate only one Brazil nut a day, you would never be deficient in selenium, says Donald J. Lisk, at Cornell University. English walnuts are a supersource of omega-3 fatty acid, which is considered the main lifesaving agent in fish. Walnuts have five times more omega-3 than any other nut. Very few plant foods have any at all.
Walnuts also are high in antioxidant anti-cancer ellagic acid.
Almonds are exceptionally high in vitamin E, which helps thwart artery clogging, boosts immunity and may help prevent cancer. In-shell nuts should be free of cracks or holes. Shake the nuts. If the nutmeat rattles, it's old and shriveled. Taste bulk nuts before buying to be sure they are not stale.