Postmenopausal women who take multivitamins appear to have the same risk of most common cancers, cardiovascular disease or dying of any cause as women who do not take multivitamin supplements, according to a report in the February 9 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
About half of Americans use dietary supplements, spending more than $20 billion per year on these products, according to background information in the article. "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," the authors write. "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 supplements--including multivitamins, the most commonly used supplements--are lacking.
Marian L. Neuhouser, Ph.D., of the Fred Hutchinson Cancer Research Center, Seattle, and colleagues analyzed data from participants in the Women's Health Initiative (WHI): 161,808 women from three clinical trials testing hormone therapy, dietary modification and vitamin D supplements and 93,676 women who were part of an observational study. The women enrolled in the WHI between 1993 and 1998; information about vitamin use was collected through interviews and by supplement bottles brought to clinic visits.
A total of 41.5 percent of the participants used multivitamins. Through 2005 (a median or midpoint of eight years of follow-up for the clinical trials and 7.9 years for the observational study), 9,619 cases of breast, colorectal, endometrial, renal, bladder, stomach, lung or ovarian cancer developed; 8,751 cardiovascular events, such as heart attack and stroke, occurred; and 9,865 deaths were reported. Analyses revealed no significant associations between multivitamin use and the likelihood of developing cancer or cardiovascular disease, or of dying.
"Risk estimates did not materially change when stratified by class of multivitamins, with the exception of a possible lower risk of myocardial infarction [heart attack] among users of stress-type supplements. Many stress supplements include high doses of folic acid and other B vitamins; previous studies have supported a protective role for folic acid in relation to cardiovascular disease and its antecedent risk factors," the authors write.
"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 authors conclude. "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."
(Arch Intern Med. 2009;169:294-304. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: The WHI program is funded by the National Heart, Lung and Blood Institute, National Institutes of Health, U.S. Department of Health and Human Services. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.