According to the results of a study published in the Journal of the National Cancer Institute, men who used multivitamins more than seven times per week were almost twice as likely as nonusers of multivitamins to develop fatal prostate cancer.
Several studies have reported that higher intake of fruits and vegetables may reduce the risk of certain types of cancer. This has prompted interest in whether dietary supplements (such as multivitamins) that provide some of the antioxidant micronutrients found in fruits and vegetables may also reduce cancer risk. There is limited evidence that antioxidant supplements reduce cancer risk, however, and some studies have even suggested that they may increase cancer risk in certain populations.
To assess the relationship between multivitamin use and risk of prostate cancer, researchers evaluated information from the National Institutes of Health (NIH)-AARP Diet and Health Study. The study enrolled 295,344 men who were free of cancer at the start of the study.
During five years of follow-up, prostate cancer was diagnosed in 10,241 of the study participants. The prostate cancer was localized in 8,765 cases and advanced in 1,476. There were 179 prostate cancer deaths.
- There was no link between multivitamin use and risk of localized prostate cancer.
- High levels of multivitamin use were linked with an increased risk of advanced or fatal prostate cancer. Compared to nonusers of multivitamins, men who used multivitamins more than seven times per week had a 32% increased risk of advanced prostate cancer and an almost twofold increased risk of fatal prostate cancer.
- The links between high levels of multivitamin use and advanced or fatal prostate cancer were strongest among men with a family history of prostate cancer, and also among men who took individual micronutrient supplements (such as selenium, beta-carotene, or zinc) in addition to multivitamins.
The researchers conclude, “The possibility that men taking high levels of multivitamins along with other supplements have increased risk of advanced and fatal prostate cancers is of concern and merits further evaluation.”
An accompanying editorial notes that these results “add to the growing evidence that questions the beneficial value of antioxidant vitamin pills in generally well-nourished populations and underscore the possibility that antioxidant supplements could have unintended consequences for our health.”
 Lawson KA, Wright ME, Subar A et al. Multivitamin use and risk of prostate cancer in the National Institutes of Health-AARP Diet and Health Study. Journal of the National Cancer Institute. 2007;99:754-64.