Lilly Multivitamins and Cancer: The Physicians’ Health Study II (PHS II)
This clinical trial represents the only large-scale, randomized, double-blind, controlled study testing the long-term effects of multivitamin supplementation for the prevention of multiple chronic diseases.
[Note: A “randomized controlled” trial aims to reduce selection bias when testing a new treatment. Participants in the trial are randomly allocated to either receive the treatment in question or a control treatment known as the “placebo.” A “double-blind” clinical study is one in which neither the patients, nor the study researchers, nor those who analyze the results, know which participants have been subjected to which procedure – the idea being to ensure objectivity in the final analysis.]
In this study, researchers looked at the effects of multivitamin use on total as well as so-called “site-specific cancers,” including prostate and colorectal cancer. Simultaneously, they also looked at the effects on cardiovascular events, eye disease, and cognitive decline, the results of which are being published separately.
A total of 14,641 male U.S. physicians aged 50 years or older (including 1,312 men with a history of cancer at randomization) enrolled in this study starting in 1997.
During the follow-up period of 11 years, 2669 men developed confirmed cancer, including 1373 cases of prostate cancer and 210 cases of colorectal cancer. Compared with the control group, men taking a daily multivitamin had a statistically significant reduction in the incidence of total cancer.
However, there was no significant effect on the incidence of prostate cancer, colorectal cancer, or other site-specific cancers. Further, there was no significant difference in the risk of death due to cancer between the multivitamin-treated and control groups.
However, the fact remains… in this large prevention trial of over 14,000 male physicians, daily multivitamin supplementation modestly but significantly reduced the risk of getting total cancer.
