A study with 161,808 postmenopausal women aged between 50 and 79, reportedly the largest study ever conducted on this demographic group, found that multivitamins had no effect on the risks related to cardiovascular disease, and a range of cancers.
The study, published in the Archives of Internal Medicine, concludes that, while nutrition should remain a principle focus for the prevention of chronic diseases, it is unlikely that multivitamin supplements have a role to play.
“What this paper shows is that multivitamin use just doesn’t seem to make that much of a difference in this population,” said co-author Sylvia Wassertheil-Smoller from Albert Einstein College of Medicine of Yeshiva University. “It confers no additional benefit but it also does no harm.”
According to a National Institutes of Health (NIH) State-of-the-Science Panel, half of the American population routinely use dietary supplements, with their annual spend estimated at over $20 billion.
The researchers, led by Marian Neuhouser from the Fred Hutchinson Cancer Research Center in Seattle, collected data from 161,808 postmenopausal women taking part in the WHI Clinical Trials and the WHI Observational Study. Of the study participants, 41.5 per cent used multivitamins, with multivitamins with minerals the most common form (35 per cent).
After an average follow-up period of 8.0 and 7.9 years in the clinical trial and observational study cohorts, respectively, the researchers concluded that multivitamin supplements had little or no influence on the risk of CVD, and breast, colorectal, endometrial, kidney, bladder, stomach, ovary, or lung cancer. No association was found either for multivitamin use and the risk of total mortality in the women.
“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,” said Dr Wassertheil-Smoller.
The authors noted several limitations, including that the results relate only to postmenopausal women, and therefore they cannot be extrapolated to the general public.
Furthermore, the follow-up time may have been insufficient for cancers that take many years to develop. Colorectal cancer, for example, has a latency period of between 10 and 20 years.
A more definitive answer on the use of these supplements can only be ascertained from randomised control trials, said the researchers. One such trail is the Physician’s Health Study, which is looking at the use of a commonly used multivitamin, Centrum Silver, compared to placebo, in thousands of male physicians. The results are expected 2012.
“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,” said Dr Wassertheil-Smoller.
Commenting on the results, Andrew Shao, PhD, vice president, scientific and regulatory affairs, for the Council for Responsible Nutrition (CRN), a trade association, said: “From a practical standpoint, this study does not change the fact that the majority of consumers could benefit from taking an affordable multivitamin, particularly as the majority of Americans fail to consume the recommended amounts of a variety of essential nutrients established by the Institute of Medicine.
“It is better to meet these recommendations than not, and consistently taking a multivitamin over the long-term, could help fill these nutrient gaps and may help consumers lead healthier lives,” he said.
Dr Shao added that, as the authors themselves noted, users of multivitamins are likely to be healthier and live healthier lifestyles.
“In other words, the key to good health is a commitment to an overall wellness approach and that includes daily use of a multivitamin,” said Dr Shao.
Source: Archives of Internal Medicine9 February 2009, Volume 169, Number 3, Pages 294-304“Multivitamin Use and Risk of Cancer and Cardiovascular Disease in the Women's Health Initiative Cohorts”Authors: M.L. Neuhouser, S. Wassertheil-Smoller, C. Thomson, A. Aragaki, G.L. Anderson, J.E. Manson, R.E. Patterson, T.E. Rohan, L. van Horn, J.M. Shikany, A. Thomas, A. LaCroix, R.L. Prentice