February 9, 2009 — (BRONX, NY) — The largest study ever conducted on postmenopausal women shows that multivitamins may offer no benefit in reducing the risk of common cancers, cardiovascular disease or overall mortality. The study, published today in Archives of Internal Medicine, also shows that multivitamins do not increase the risk for these conditions.
Dr. Sylvia Wassertheil-Smoller The research was conducted as part of the Women's Health Initiative Clinical Trials and the Women's Health Initiative (WHI) Observational Study. Combined, the two studies include data from 161,808 postmenopausal women ages 50 to 79. Of that group, 41.5 percent used multivitamins over 15 study years. This latest study found no overall associations between multivitamin use and breast, colorectal, endometrial, kidney, bladder, stomach, ovary, or lung cancer. Researchers also found no association between multivitamin use and cardiovascular disease and death.
The study was led by Marian L. Neuhouser, Ph.D., R.D., of the Fred Hutchinson Cancer Research Center in Seattle, Washington, in conjunction with others from national WHI clinical centers, including Sylvia Wassertheil-Smoller, Ph.D., professor of epidemiology and population health at Albert Einstein College of Medicine of Yeshiva University. Dr. Wassertheil-Smoller is the principal investigator of the WHI study at Einstein.
Researchers collected data for the multivitamin study during participants' clinic visits. Clinic staff transcribed the ingredients for each supplement, and then grouped them according to three classifications. The most common category (35 percent) was multivitamins with minerals, followed by multivitamins alone (3.5 percent) and stress multivitamins (2.3 percent).
"Based on our results, 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," explained Dr. Wassertheil-Smoller.
According to the most recent information from the National Institutes of Health published in Archives of Internal Medicine, more than half of Americans use supplements; over $20 billion is spent annually on dietary supplements, with more than one-third of this amount spent on multivitamins. The National Health and Nutrition Examination Surveys show that women are more likely than men to take supplements, and the number of women taking supplements increases steadily among women 30 years of age and up.
Information on whether multivitamins promote health benefits or risks can be confusing to consumers. Clinical studies show folic acid can offer protection from birth defects for women of childbearing age, while other studies suggest antioxidants, especially beta-carotene among smokers, could increase cancer risk.
The WHI study authors acknowledge the potential limitations of their study, and caution against extrapolating their results to the general public. For example, the cohort of women participating in the study was relatively well-educated and had better health habits. Approximately 40 percent had a college degree or higher, and at least 80 percent finished high school.
"What this paper shows is that multivitamin use just doesn't seem to make that much of a difference in this population," says Dr. Wassertheil-Smoller. "It confers no additional benefit but it also does no harm."
Despite the large number of study participants, the researchers emphasize the need for more definitive randomized control trials on multivitamin use. Randomized control studies (RCS) compare treatment groups with placebo groups and are considered the gold standard in clinical research. The first ongoing RCS on multivitamin use in men will be completed in 2012. That study, the Physician's Health Study, looks at thousands of male physicians and compares a commonly used multivitamin, Centrum Silver®, to placebo.
"What is encouraging now is that there is a scientific focus on the biological and physiological mechanisms through which these vitamins and minerals work. I am really curious to see their results," Dr. Wassertheil-Smoller said.
Dr. Wassertheil-Smoller does not think another randomized control study, on women for example, will be done until after results from the men's study are completed and the findings are published.
The paper, "Multivitamin Use and Risk of Cancer and Cardiovascular Disease in the Women's Health Initiative Cohorts" appears in the February 9 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
Multiple authors and institutions contributed to this paper, including Marian L. Neuhouser, Aaron Aragaki, Garnet L. Anderson, Andrea LaCroix, and Ross L. Prentice of the Fred Hutchinson Cancer Research Center, Seattle, WA; Ruth E. Patterson of Fred Hutchinson Cancer Research Center and Amylin Pharmaceuticals, Inc., San Diego, CA; Sylvia Wassertheil-Smoller and Thomas E. Rohan of Albert Einstein College of Medicine, Bronx, NY; Cynthia Thomson, University of AZ, Tucson, AZ; JoAnn Manson, Harvard Medical School, Boston, MA; Linda van Horn, Northwestern University, Chicago, IL; James M. Shikany, University of Alabama at Birmingham, Birmingham, AL; and Asha Thomas, Medstar Research Institute, Washington D.C.
The WHI is sponsored by the National Heart, Lung, and Blood Institute (NHLBI) of the National Institutes of Health (NIH).