The Physicians Health Study II was designed as a randomized clinical trial with three specific primary goals:
- To determine whether vitamin E every other day reduces the risk of developing prostate cancer in older healthy male physicians
- To determine whether daily ascorbic acid (vitamin C) and/or a multivitamin reduces the risk of total cancer in these participants
- To determine whether vitamin E every other day, ascorbic acid daily, or a multivitamin daily reduces the risk of important vascular events in these participants
The trial enrolled over 14,600 participants. All the participants were male physicians of 50 years or older.
The overall goal of this trial was to discover how well vitamin E, ascorbic acid, and/or multivitamins compared to a placebo in preventing prostate cancer, other cancers, or cardiovascular disease in healthy, older, male doctors.
The full results of this trial were published in the Journal of the American Medical Association in January 2009, and the complete paper is accessible on line. According to the detailed report:
- The trial began in 1997 and continued until its scheduled completion on August 31, 2007.
- The total enrollment of 14,641 male physicians initially aged 50 years or older included 1,307 men with a history of prior (but not prostate) cancer at randomization.
- Patients receiving active ingredients received individual supplements of 400 IU of vitamin E every other day and 500 mg of vitamin C daily.
- During a mean follow-up of 8.0 years, there were 1,008 confirmed incident cases of prostate cancer and 1,943 total cancers.
- Compared with placebo, vitamin E had no effect on the incidence of prostate cancer or total cancer.
- There was no significant effect of vitamin C on total cancer or prostate cancer.
- 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.
The investigators concluded that in “this large, long-term trial of male physicians, neither vitamin E nor C supplementation reduced the risk of prostate or total cancer.” They further stated that, “These data provide no support for the use of these supplements for the prevention of cancer in middle-aged and older men.”