Some foods just go together-peanut butter and jelly, cheese and crackers, peas and carrots. But some foods that taste great together are also more nutritious when eaten in combination. Here are three powerful pairs that are better together:

Power-Food Pairing: Whole Grains with Garlic or Onions
Adding sautéed onions or garlic to whole-grain dishes takes them beyond ordinary-and new research suggests it can make whole grains healthier too. The study, published in the Journal of Agricultural and Food Chemistry, found that combining garlic and/or onions with whole grains may help boost the absorption of iron and zinc-minerals that are absorbed less easily from plant sources than animal sources. (Iron helps shuttle oxygen to cells; zinc is needed for healthy immunity and repairing wounds.) Researchers don't know exactly how, but speculate that sulfur compounds in onions and garlic are what help to promote absorption. (They're also what cause garlic breath.)

Power-Food Pairing: Beans and Greens
The real power couple here is iron (found in beans) and vitamin C (in greens). When you eat beans and greens together, the vitamin C in the greens helps turn the iron in the beans into a form your body can more easily absorb. This effect is especially helpful when you eat the less-easily-absorbed "nonheme" iron, found in nonanimal sources, such as tofu, spinach, raisins and fortified cereal (meat, fish and poultry deliver heme iron, which your body absorbs more easily). More sources of vitamin C beyond leafy greens: citrus fruits, cauliflower, red bell peppers, parsley and papaya.

Power-Food Pairing: Tomatoes and Olive Oil
Adding fat, such as oil, to fruits and vegetables can help you better absorb some of their healthy phytonutrients. A recent study in Free Radical Biology and Medicine found that people who ate several servings of tomato products paired with either sunflower oil or olive oil upped their lycopene levels by the end of a week. (Lycopene is a compound that gives tomatoes, red peppers and watermelons their red color and has been linked to a reduced risk of breast cancer, heart disease and lung disease.) But olive oil may be a healthier pick. Compared to the group that ate sunflower oil, those who got olive oil had higher antioxidant levels.

More from EatingWell: