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Selenium

Why you need it: Selenium is a mineral with antioxidant properties. The body only requires small amounts of it, but it plays a large role in preventing chronic diseases. It also helps regulate thyroid function and the immune system.

Where to get it: Just six to eight Brazil nuts provide 544 mcg of selenium—that's 777% of your DV. Too much selenium can actually be harmful, however, so stick with the mineral's number-two food source—canned tuna (68 mg per 3 ounces, or 97% DV)—except on special occasions.

Try this recipe: Sicilian Tuna and White Bean Bruschetta

Next: Thiamin