Vitamins: Separating Fact From Fiction
Experts cut through the hype about the health benefits of vitamin supplements.
Choosing a Supplement
It's easy to become overwhelmed when looking at the dietary supplement shelves of a health food store or even your local supermarket. While many of the health claims are unproven or downright bogus, some supplements may be useful for some groups.
Major multivitamin makers typically produce different varieties for men, women, children and older folks. Picking a pill that fits your group makes sense, says dietitian Grotto, as the optimal level of various nutrients varies by age and sex. For example, premenopausal women need more iron than children or the elderly, he says.
But the elderly have a harder time obtaining adequate amounts of vitamin B-12 from natural sources, so the need for supplementation may increase with age, says Lynn Bailey, a University of Florida nutritionist who teaches courses on vitamins.
Folate, or folic acid, is key to preventing birth defects (such as spina bifida), Bailey says. Bailey says all women of childbearing age should ensure they get 100% of the RDA of folic acid through fortified food or a multivitamin.
Calcium and Vitamin D
Calcium supplements are also important for certain age groups, Bailey says. The Institute of Medicine, part of the National Academy of Sciences, recommends that adolescents get 1,300 milligrams of calcium a day. One cup of milk or calcium-fortified orange juice contains about 300 milligrams of calcium.
Other sources of calcium include cheese, tofu, yogurt, vegetables, and beans. A typical calcium supplement may contain 500 milligrams or 600 milligrams of calcium. Bailey gives her 15-year-old son a daily calcium supplement at dinnertime. People over 50 should get 1,200 milligrams a day of calcium to ward off osteoporosis (thinning of the bones), Bailey says.
Federal dietary guidelines recommend that the elderly, the homebound, and people with dark skin boost their vitamin D intake with both fortified foods and supplements to reduce the risk of bone loss. Vitamin D helps with absorption of calcium; often calcium supplements will also contain vitamin D. (The full federal guidelines, updated in 2005, are available at www.health.gov/dietaryguidelines.)
Special groups such as smokers, pregnant women, or people recovering from traumatic injury may need additional supplements, Cross says. Decisions to take supplements beyond a multivitamin are best made with your doctor or registered dietitian, she says.
The evidence is strong that a healthy diet can ward off chronic diseases like cancer and heart disease. What's less clear is if big intakes of particular micronutrients can boost that preventive effect further.
There is promising evidence that the mineral selenium could prevent a variety of cancers, says Alan Kristal, DrPh, associate chief of cancer prevention at the Fred Hutchinson Cancer Research Center in Seattle. But beyond selenium, the data aren't promising, Kristal says. For example, there's no solid evidence that taking large doses of antioxidants like vitamins B or C have any beneficial effect.