Study: Vitamins E and C Fail to Prevent Cancer in Men

Published: November 18, 2008

A large clinical trial of almost 15,000 male doctors taking vitamins E and C for up to 10 years has found that neither supplement had any effect on cancer rates, including cancer of the prostate.

The study comes on the heels of a disappointing finding regarding vitamin E reported late last month. After following 35,000 men taking selenium and vitamin E, investigators halted their trial because no benefit was seen and in some supplement users there appeared to be a slight increase in the risk of cancer or diabetes.

An author of the current study, an abstract of which was presented on Monday at the American Association for Cancer Research meeting in Washington, D.C., said his trial found neither risk nor benefit to use of the vitamins.

“The good news is you don’t appear to be hurting yourself ,” said Howard D. Sesso, an assistant professor of medicine at Brigham and Women’s Hospital. But, he added, “There’s very little evidence to recommend taking these supplements for prevention of cancer, particularly in the case of vitamin E.”

The evidence regarding vitamin C is not as clear, since fewer large trials of vitamin C have been carried out, he said.

Dr. Andrew Shao, vice president for scientific and regulatory affairs at the Council for Responsible Nutrition, a trade association representing the supplement industry, said the group of physicians who participated in the trial were not necessarily representative of the general population. If they were healthier overall and ate a more nutritious diet, he said, it would be hard to detect a clear difference between the supplement users and those taking a placebo.

J. Michael Gaziano;    JAMA. 2009;301(1):52-62

Many individuals take vitamins in the hopes of preventing chronic diseases such as cancer, and vitamins E and C are among the most common individual supplements. A large-scale randomized trial suggested that vitamin E may reduce risk of prostate cancer; however, few trials have been powered to address this relationship. No previous trial in men at usual risk has examined vitamin C alone in the prevention of cancer.

To evaluate whether long-term vitamin E or C supplementation decreases risk of prostate and total cancer events among men. The Physicians' Health Study II is a randomized, double-blind, placebo-controlled factorial trial of vitamins E and C that began in 1997 and continued until its scheduled completion on August 31, 2007. A total of 14 641 male physicians in the United States initially aged 50 years or older, including 1307 men with a history of prior cancer at randomization, were enrolled. Intervention  Individual supplements of 400 IU of vitamin E every other day and 500 mg of vitamin C daily.

Results  During a mean follow-up of 8.0 years, there were 1008 confirmed incident cases of prostate cancer and 1943 total cancers. Compared with placebo, vitamin E had no effect on the incidence of prostate cancer (active and placebo vitamin E groups, 9.1 and 9.5 events per 1000 person-years; hazard ratio [HR], 0.97; 95% confidence interval [CI], 0.85-1.09; P = .58) or total cancer (active and placebo vitamin E groups, 17.8 and 17.3 cases per 1000 person-years; HR, 1.04; 95% CI, 0.95-1.13; P = .41). There was also no significant effect of vitamin C on total cancer (active and placebo vitamin C groups, 17.6 and 17.5 events per 1000 person-years; HR, 1.01; 95% CI, 0.92-1.10; P = .86) or prostate cancer (active and placebo vitamin C groups, 9.4 and 9.2 cases per 1000 person-years; HR, 1.02; 95% CI, 0.90-1.15; P = .80). Neither vitamin E nor vitamin C had a significant effect on colorectal, lung, or other site-specific cancers. Adjustment for adherence and exclusion of the first 4 or 6 years of follow-up did not alter the results. Stratification by various cancer risk factors demonstrated no significant modification of the effect of vitamin E on prostate cancer risk or either agent on total cancer risk.

Conclusions  In this large, long-term trial of male physicians, neither vitamin E nor C supplementation reduced the risk of prostate or total cancer. These data provide no support for the use of these supplements for the prevention of cancer in middle-aged and older men.