Why Do Millions of Americans Take Multivitamins?
It's hard to tell whether vitamins actually improve health, because "adults who use dietary supplements tend to report more healthy lifestyles," Bailey said. "They report better overall health, more exercise, moderate alcohol consumption and are more likely to [have never smoked] or be former smokers."
A clear role exists for some dietary supplements -- such as folic acid to reduce the risk of birth defects. Calcium and vitamin D play an important role in bone health, Bailey said.
Duffy MacKay, a spokesman for the supplement industry, said taking a multivitamin and other supplements is part of a healthy lifestyle.
"People who take a multivitamin in combination with a healthy diet, exercising regularly and practicing stress management are people who live long and prosperous," said MacKay, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition.
Two recent studies highlight the ongoing debate on the value of multivitamins.
One, published in the Nov. 7 issue of the Journal of the American Medical Association, found that multivitamins will do nothing to help stave off heart disease, heart attack or stroke.
Yet another study published in the Oct. 17 issue of the same journal found that men who take multivitamins every day for several years may lower their risk of cancer by a small amount.
Another expert weighed in on the discussion.
Although vitamin and mineral supplements may be of benefit in certain instances, they cannot take the place of eating a variety of healthy foods every day, said Samantha Heller, an exercise physiologist and clinical nutrition coordinator at the Center for Cancer Care at Griffin Hospital in Derby, Conn.
"I wish that a portion of the $30 billion spent on dietary supplements was spent on healthy foods and gym memberships," Heller said.
For more about multivitamins, visit the U.S. National Library of Medicine.