Multivitamin Use: No Effect on Cancers or CVD in Women

February 10, 2009 (Seattle, Washington) — Multivitamin use has no influence on the risk of common cancers, cardiovascular disease, or overall mortality, according to a new analysis of more than 160 000 women participating in the Women's Health Initiative (WHI) clinical trials [1]. Dr Marian L Neuhouser (Fred Hutchinson Cancer Research Center, Seattle, WA) and colleagues report their findings in the February 9, 2009 issue of the Archives of Internal Medicine.
"The main message of our study is that postmenopausal women who take a multivitamin don't increase their risk for cancer or cardiovascular disease, but they don't decrease it either," Neuhouser told heartwire. "These multivitamins are having no effect with regard to these particular disease outcomes."
"Consumers need to decide if they want to continue this practice if they are taking [multivitamins] in order to prevent getting cancer or CVD," she added. "There may be other preventive practices that are better than taking a vitamin supplement, and their money is probably better spent on buying fruit and vegetables or increasing physical activity."
"These Pills Are of Little Value"
The study included 161 808 participants from the WHI; detailed data were collected on multivitamin use at baseline and follow-up time points, with enrollment occurring between 1993 and 1998 and a median follow-up period of around eight years. Nearly half of the participants (41.5%) reported using multivitamins on a regular basis.
Disease end points were collected through 2005 and included cancers of the breast (invasive), colon/rectum, endometrium, kidney, bladder, stomach, ovary, and lung; CVD (myocardial infarction, stroke, and venous thromboembolism); and total mortality.
Over the follow-up period, there were 9619 cases of cancer, 8751 CVD events, and 9865 deaths reported. Multivariate adjusted analyses revealed no association of multivitamin use with risk of any cancer (hazard ratio, 0.98), CVD (HR, 0.96), or total mortality (HR, 1.02).
Neuhouser said there was no particular positive (or negative) trend for any individual cancer or CVD end point, with the exception of "a slightly decreased risk for MI in those who took stress multivitamins--the ones that have high doses of B vitamins, vitamin C, zinc, and selenium--but because there were so few cases in this group, only 64 MIs among all these women, it's a little bit hard to draw a firm conclusion, so we didn't want to draw particular attention to this," she noted.
"The evidence is accumulating that these are pills of little value," she said, referring to recent neutral results from trials with multivitamins in men--the US-based SELECT trial and the Physician's Health Study 2--that were not available when her manuscript was submitted.
No Policing of the Supplements Industry
Neuhouser also criticizes the deregulation of the supplement industry that occurred in the US in the early 1990s with the introduction of the Dietary Supplement and Health Education Act. "The FDA has a small amount of jurisdiction, but it's an unfunded mandate and their meager budget means they don't really have any policing power over this," she noted.
"We have entire aisles in our grocery stores, with all kinds of vitamins, minerals, and so forth. Some are generic or store brand and so not that expensive, but some are extremely expensive. I hate to have consumers spending money on something that may not help them at all, when they could probably better spend it on healthy foods," she concluded.