"I am glad that you alerted me to the danger of "overdosing" with calcium. My wife needs to know this! "
At their best, vitamin and mineral supplements help fill nutrient gaps when the diet is lacking. Supplements may be most useful to people who can’t afford a variety of healthful foods (a basic multivitamin/mineral supplement taken daily can cost as little as $15 per year). People in age groups that require higher intakes for some nutrients (e.g., calcium for teenagers and postmenopausal women) may also benefit from supplement use, as can people who follow special diets for medical (e.g., lactose intolerance) or ethical (e.g., veganism) reasons. Since federal nutrition surveys suggest that considerable numbers of Americans may be falling short on a handful of specific nutrients (vitamin A, vitamin C, vitamin E, calcium and magnesium), some experts recommend that all adults take a multivitamin/mineral supplement—one that delivers no more than 100 percent of recommended daily doses—as “dietary insurance.” Other experts argue that these surveys don’t accurately account for nutrients Americans get through fortified foods, and say that taking a supplement may enable poorer food choices (“Oh, I had a multi this morning, so I’ll have a cookie, instead of an orange and almonds, for a snack”).
Though the NIH panel generally cited “lack of evidence” for supplements’ benefits, it emphasized that even for consistently healthy eaters, special circumstances warrant the use of supplements. Women who could become pregnant should take supplemental folic acid, as multiple studies suggest folic acid is better absorbed than food folate and helps reduce the risk of a neural-tube birth defect. Postmenopausal women are encouraged to take calcium and vitamin D supplements: the combination appears to decrease the risk of fractures. People with age-related macular degeneration—a condition in which the center of the retina deteriorates—should consider taking antioxidants. Mounting research suggests that free-radical damage accelerates the condition, and one well-designed clinical trial showed that supplementing with antioxidants, including vitamins C and E, beta carotene and zinc, slowed progression of the disease.
The irony of dietary supplements, however, is that “the people who need supplements most take them least,” says Nestle. And the reverse is true: “Most supplements are taken by people whose diets are just fine without them.” Indeed, research consistently shows that people who use dietary supplements generally have better diets; they exercise more and smoke less. What’s more, emerging research suggests some people taking supplements are getting too much of certain nutrients.