Study: Multivitamins Slightly Reduce Cancer in Men Over 50

Harvard researchers have found a possible link between taking a daily multivitamin over a long period of time and a small reduction in cancer. They analyzed data from the Physicians’ Health Study (PHS) II, which tested the effects of multivitamins in 14,641 male doctors 50 years of age or older. PHS II participants received either a multivitamin or a placebo for an average of about 11 years. The study was published early online Oct. 17, 2012 in the Journal of the American Medical Association.

The main finding from the study is a small, but significant 8% reduction in new cancer cases among the men who took the multivitamins. However, the reduction dropped to below a significant level when researchers looked at men who had no history of cancer; the benefit appeared to be limited to men who already had a history of cancer. Also, when researchers looked at specific types of cancer, they found no effect. For example, taking multivitamins had no effect on the risk of getting prostate cancer, colon and rectal cancer, lung cancer, or bladder cancer.

Despite the reduction they observed in new cancer cases, researchers found no significant reduction in deaths due to cancer among the men who took the multivitamins.

While the results are potentially promising, the study was limited to a select group of fairly healthy men, so it is not clear how the findings might apply to other groups of people, or if different multivitamin formulas might yield different results.

Susan M. Gapstur, PhD, MPH, American Cancer Society vice president, Epidemiology Research Program, commented on the findings: "This well-designed randomized clinical trial suggests that a daily multivitamin was associated with a modest reduction in cancer risk in older non-smoking men. But it's important to remember that this study, as credible as it is, is still just one trial. Typically, we like to see these kinds of findings replicated by other studies, and in other populations, before coming to solid conclusions.

"Probably the most important limitation of this study is the fact that it was done in older men, the great majority of whom were non-smokers. Whether this protective association will be found in women or in high risk populations, such as smokers, is unclear. We'll need further studies to help sort through these issues."

Vitamin supplements and cancer

Researchers have been conducting large, randomized trials for many years to see whether taking supplements containing one or more vitamins could prevent cancer. Most of the studies concluded that people who took the vitamins were not less likely to get cancer than people who took a placebo. In some studies, people taking the vitamins actually got more cancer.

According to Dr. Gapstur, "Results of previous trials of vitamin and or mineral supplementation for cancer prevention have been mixed, and some studies of individual nutrients have shown evidence of possible harm. A daily multivitamin, as used in the current study, contains more nutrients and usually in smaller doses than those studied in trials of individual nutrients.

"For years, the American Cancer Society has recommended getting nutrients from a healthy diet, and has recommended that for people who choose to take supplements, the best choice is a balanced multivitamin/mineral supplement containing no more than 100% of the Daily Value of most nutrients. This study is an important addition to the body of evidence the Society reviews in establishing its guidelines."

Read more about vitamins and cancer in the Expert Voices blog written by American Cancer Society nutritional expert Marji McCullough, ScD, RD.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Multivitamins in the Prevention of Cancer in Men. Published early online October 17, 2012 in the Journal of the American Medical Association. First author: J. Michael Gaziano, MD, MPH, Brigham and Women’s Hospital and Harvard Medical School, Boston, Mass.

American Cancer Society news stories are copyrighted material and are not intended to be used as press releases. For reprint requests, please see our Content Usage Policy.