Vitamin E or Vitamin C Taken Longterm Has No Anti-Cancer Effect
A large-scale prevention trial has shown no protective effect from vitamin E on prostate cancer or vitamin C supplementation on total cancer.
The Physicians’ Health Study II is a large-scale, long-term, randomized clinical trial that included 14,641 physicians who were at least 50 years old at enrollment. These physicians were given 400 IU of vitamin E every other day or a look-alike sham pill (a placebo) or 500 mg of vitamin C daily or its placebo.
Researchers followed these study-subjects for up to 10 years for the development of cancer. The analyzed results show that doctors randomized to take genuine vitamin E were not protected from prostate cancer. This lack of effect for vitamin E also extended to total cancer. Vitamin C had a similar lack of effect on total cancer.
“After nearly 10 years of supplementation with either vitamin E or vitamin C, we found no evidence supporting the use of either supplement in the prevention of cancer,” said Howard D. Sesso, Sc.D., M.P.H., an assistant professor of medicine at Brigham and Women’s Hospital. “While vitamin E and C supplement use did not produce any protective benefits, they also did not cause any harm,” he added.
Moreover, analysis of data from the same large group of US male physicians enrolled as study subjects found no benefit from vitamin E or C for the prevention of heart disease. Dr. Sesso and team write in the JAMA: “In this large, long-term trial of male physicians, neither vitamin E nor vitamin C supplementation reduced the risk of major cardiovascular events. These data provide no support for the use of these supplements for the prevention of cardiovascular disease in middle-aged and older men.”
Previously, people who reported eating a diet rich in vitamins E and C were found to have a lower risk of cancer. These earlier laboratory research and observational studies had suggested that taking these vitamins as individual supplements may offer some protective benefits.
J. Michael Gaziano, M.D., associate professor of medicine at Brigham and Women’s Hospital and VA Boston, another investigator for this study, said, “Individual vitamin supplements such as vitamin E and C do not appear to provide the same potential advantages as vitamins included as part of a healthy, balanced diet.”
This study is considered particularly reliable with respect to accurate feedback. The participants had high rates of completion of annual questionnaires, and the researchers followed up to confirm all reports of cancer.
Finally, Sesso said that these results provide clinically meaningful new information. “Our results represent one of only a few clinical trials that have tested this idea. The final component of the Physicians’ Health Study II, testing daily multivitamin supplementation, remains ongoing.”
The results were presented at the American Association for Cancer Research’s Seventh Annual International Conference on Frontiers in Cancer Prevention Research
The AACR publishes five major peer-reviewed journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. The AACR also publishes CR, a magazine for cancer survivors and their families, patient advocates, physicians and scientists.