MAY 2009

IF YOU’RE COUNTING on that daily multivitamin pill to help protect you against cancer or heart disease, think again. The largest study ever of multivitamin use among older women has found that the pills made no significant difference in the risk of cancer, heart disease or overall mortality.

About half of Americans use dietary supplements, including multivitamins, which are the most commonly used supplements, spending about $23 billion annually. Publishing their research in the Archives of Internal Medicine, Marian L. Neuhouser, PhD, of the Fred Hutchinson Research Center and colleagues commented, “The motivations for supplement use vary, but common reasons include the belief that these preparations will prevent chronic diseases, such as cancer and cardiovascular disease. These views are often fueled by product health claims, consumer testimonials and an industry that is largely unregulated owing to the 1994 Dietary Supplement and Health Education Act.” Scientific data supporting the benefits of most supplements are lacking, the researchers added.

So Neuhouser and colleagues analyzed data on 161,808 postmenopausal women participating in four parts of the Women’s Health Initiative (WHI). A total of 41.5% of the women used multivitamins. Over an average of about eight years of followup, there were 9,618 cases of cancer, 8,751 cardiovascular-disease events and 9,865 deaths.

The researchers found no association between multivitamin use and risk of any type of cancer or risk of dying. Nor was there any statistically significant benefit seen from multivitamins in preventing any type of cardiovascular disease, except for multivitamins that claim to fight stress. These supplements, which typically contain high doses of folic acid and other B vitamins, had a possible protective association against heart attack.

Not even women who took multivitamins for a long time showed any difference in risk compared to non-multivitamin users or those who took the pills for just a short period.

“These results suggest that multivitamin use does not confer meaningful benefit or harm in relation to cancer or cardiovascular disease risk in postmenopausal women,” the researchers concluded. “Nutritional efforts should remain a principal focus of chronic disease prevention, but without definitive results from a randomized controlled trial, multivitamin supplements will not likely play a major role in such prevention efforts.”

Neuhouser, the study’s lead author, added this straightforward advice: “Get nutrients from food. Whole foods are better than dietary supplements.”

THE NEW STUDY adds to a growing drumbeat of negative findings about vitamin supplements. Recently, a lengthy study of male physicians found no benefit from supplements of vitamins C or E against heart disease or cancer, and another study of vitamin E and selenium supplements against prostate cancer was stopped after disappointing results and concerns about adverse effects (see the February 2009 Healthletter).

Nonetheless, consumers keep buying vitamin pills and other supplements. “I’m puzzled why the public in general ignores the results of well-done trials,” Eric Klein, MD, of the Cleveland Clinic, national coordinator of the prostate-cancer study, told The New York Times. “The public’s belief in the benefits of vitamins and nutrients is not supported by the available scientific data.”

“We call them ‘essential nutrients’ because they are,” Neuhouser added. “But there has been a leap into thinking that vitamins and minerals can prevent anything from fatigue to cancer to Alzheimer’s. That’s where the science didn’t pan out.”

The WHI study is important because it is the largest, most comprehensive of its kind, commented Tufts' Alice H. Lichtenstein, DSc, who was not one of the researchers. She added, “All the evidence keeps pointing in the same direction; it is the whole diet that makes a difference when it comes to health outcomes, not dietary supplements.”

Some previous studies had suggested a benefit for multivitamins. Those results were confounded, however, by the fact that people who choose multivitamins also tend to choose other positive health behaviors.

One co-author of the new study, JoAnn Manson, MD, DrPH, chief of preventive medicine at Brigham & Women’s Hospital, said that despite the negative results, multivitamins may be useful for some people as “a form of insurance” against poor eating habits. That echoes an argument long made by the supplement industry.

But another of the researchers, Sylvia Wassertheil-Smoller, PhD, from Albert Einstein College of Medicine, summarized the findings: “If you fall into the category of the women described here, and you do in fact have an adequate diet, there really is no reason to take a multivitamin.”

TO LEARN MORE: Archives of Internal Medicine, Feb. 9,2009; abstract at archinte.ama-assn.org/cgi/content/abstract/169/3/294.