Calcium: An adequate intake of calcium can help prevent or reduce bone loss and, in older women, reduce the risk of fractures. Women between 19 and 50 (including those who are pregnant and breastfeeding) need 1,000 milligrams a day, according to the Institute of Medicine; women over 50 need 1,200 milligrams a day. You should get as much calcium as you can from foods. But many women don’t get enough through diet alone. In that case, taking a supplement is recommended. You also need to be sure you are getting enough vitamin D, which is involved in calcium absorption, and other nutrients.
Folate (folic acid): All women of childbearing age should consume 400 micrograms of this B vitamin daily. Folate helps protect against birth defects called neural tube defects, which include spina bifida. If you can’t be sure you are getting enough from your diet (leafy greens and beans are good sources, and many grain products are fortified with folate), you should take a multivitamin containing at least 400 micrograms of folic acid (the term for folate in supplements).
Iron: Before age 50, you should get 18 milligrams of iron a day—8 milligrams if you are older. The average U.S. diet supplies plenty of iron from both meat and nonmeat sources. But even with a balanced diet, some menstruating and pregnant women may be at risk for iron deficiency, as may dieters, strict vegetarians and endurance athletes. If you fall into one of these groups, you may need an iron supplement. But be sure to consult your doctor first. Some people, especially those of northern European descent, have hemochromatosis—a disorder that causes them to absorb and store too much iron—so they must guard against iron overload. A blood test can help diagnose the disorder.