Editorial

Can Multivitamins Prevent Cancer and Heart Disease?

A recent large-scale double-blind trial found that regular use of a multivitamin significantly decreased the incidence of cancer by 8%, but had no significant effect on the incidence of heart disease, in a group of male physicians in the US. These findings were published in two separate reports in the Journal of the American Medical Association.^1,2 The studies received extensive press coverage but, as is often the case, the reports in the media did not tell the whole story. After reviewing this research, I have concluded that the data do not rule out the possibility that multivitamins can prevent cardiovascular disease. Furthermore, it is possible that multivitamin use decreases the risk of cancer by more than 8%.

In the two new studies, 14,641 male physicians aged 50 years or older (mean, 64.3 years) participating in the Physicians’ Health Study II were randomly assigned to receive, in double-blind fashion, a daily multivitamin (Centrum Silver) or placebo. During a median follow-up period of 11.2 years, there were 1732 major cardiovascular events and 2669 men developed cancer (excluding nonmelanoma skin cancer). With respect to heart disease, compared with placebo, multivitamin use had no significant effect on the incidence of major cardiovascular events (hazard ratio [HR] = 1.01; p = 0.91), myocardial infarction (HR = 0.93; p = 0.39), stroke (HR = 1.06; p = 0.48), or cardiovascular disease mortality (HR = 0.95; p = 0.47). In contrast, multivitamin use significantly decreased the incidence of total cancers (excluding nonmelanoma skin cancer) by 8% (HR = 0.92; p = 0.04) and decreased cancer mortality nonsignificantly by 12% (HR = 0.88: p = 0.07). Among the 1312 men with a history of cancer at baseline, multivitamin use was associated with a 27% reduction in new cancers (HR = 0.73; p = 0.02). Total mortality was nonsignificantly lower by 6% in the multivitamin group than in the placebo group.

One limitation of these studies is that physicians tend to be relatively healthy and well nourished, so the findings do not necessarily apply to other population groups, which might be less healthy or have a higher prevalence of nutritional deficiencies.

In addition, the findings from this study might not apply to other multivitamin-mineral preparations. According to the label, Centrum Silver contains (in addition to vitamins and minerals) crospovidone, butylated hydroxytoluene, FD&C Blue 2 Aluminum Lake, FD&C Red 40 Aluminum Lake, FD&C Yellow 6 Aluminum Lake, polyethylene glycol, polyvinyl alcohol, sodium aluminum silicate, sodium benzoate, talc, and titanium dioxide. It would be surprising if none of these chemicals were harmful with long-term use, and it is possible that one or more of them negated a beneficial effect of the nutrients.

In addition, Centrum Silver provides 15 mg of zinc per day. Supplementation with large doses of zinc has been shown to induce copper deficiency, and copper deficiency is known to cause cardiovascular disease in experimental animals. While 15 mg per day is not a large amount of zinc, it is conceivable that taking 15 mg daily for a number of years would decrease copper status. Considering that the average copper content of various foods has declined substantially since around 1940,³ a further decrease in copper status from long-term zinc supplementation could have adverse consequences. Centrum Silver does contain copper, but for approximately 70% of the time the Physicians’ Health Study II was being conducted it was in the form of cupric oxide, which cannot be absorbed by humans.^4,5

A number of earlier studies suggested that various vitamins and minerals can indeed help prevent heart disease, although the evidence is conflicting. The new study did not address the question of whether a better-formulated product that is free from extraneous chemicals would be beneficial.

With respect to cancer, one might speculate that the benefits of multivitamin-mineral use would have been even greater if a different preparation had been used. Since copper plays an important role in immune function, compromising copper status with long-term zinc supplementation could have impaired the body’s “immune surveillance” mechanism against cancer.

Multivitamins-mineral preparations have been shown to have a wide range of beneficial effects, including increasing energy and stress tolerance, improving pregnancy outcomes, decreasing infection rates, slowing bone loss, and improving cognitive function in some schoolchildren. While the evidence regarding prevention of heart disease and cancer remains conflicting, nothing in the new studies should dissuade people from taking a multivitamin-mineral for the purpose of improving overall health.

Alan R. Gaby, MD

Notes

1. Gaziano JM et al. Multivitamins in the prevention of cancer in men. The Physicians’ Health Study II Randomized Controlled Trial. JAMA. 2012;308:1871–1880.

2. Sesso HD et al. Multivitamins in the prevention of cardiovascular disease in men: the Physicians’ Health Study II randomized controlled trial. JAMA. 2012;308:1751–1760.

3. Worthington V. Nutritional quality of organic versus conventional fruits, vegetables, and grains. J Altern Complement Med. 2001;7:161–173.

4. Personal communication, Pfizer Consumer Healthcare. December 7, 2012.

5. Baker DH. Cupric oxide should not be used as a copper supplement for either animals or humans. J Nutr. 1999;129:2278–2279.