You've been trying to get more folate, calcium, and iron to stay healthy, but if you're on the birth control pill, you should also up your intake of vitamin B6, indicates a study published in the American Journal of Clinical Nutrition. "We found that three-quarters of women taking oral contraceptives—but not supplements—had low blood levels of B6," says Martha Savaria Morris, Ph.D., an epidemiologist at Tufts University. While the recommended intake is 1.3 milligrams of the vitamin daily, pill users may need 3 milligrams or more, she says. To get what's required to maintain a strong immune system, fill your plate with foods like chickpeas, fortified cereals, and bananas. You can also take a prenatal supplement, which often contains more B6 than a multivitamin.