Lawson KA et al. (2007) Multivitamin use and risk of prostate cancer in the National Institutes of Health–AARP Diet and Health study. J Natl Cancer Inst 99: 754–764

Multivitamin supplements are taken by 35% of adults in the US but, alarmingly, epidemiological evidence suggests that multivitamin use might be associated with more rapid progression of prostate cancer. Other data indicate that multivitamin use may protect against initiation of the disease. In a large prospective study, Lawson et al. investigated the association between multivitamin use and the risk of localized, advanced and fatal prostate cancer in 295,344 men enrolled in the NIH–American Association of Retired Persons Diet and Health Study.

All participants were cancer free at enrollment (1995–1996), when information on use of multivitamin and individual supplements during the preceding 12 months was obtained by questionnaire. Prostate cancer was diagnosed in 10,241 participants (8,765 localized and 1,476 advanced) during 5 years follow-up. Mortality analysis (6 years of follow-up) identified 179 cases of fatal prostate cancer. After adjustment for prostate cancer risk factors, multivitamin use was not associated with the risk of localized prostate cancer. By contrast, men who reported excessive use of multivitamin supplements (more than seven times per week) had an increased risk of advanced and fatal prostate cancer compared with never users (relative risk 1.32 [95% CI 1.04–1.67] and 1.98 [95% CI 1.07–3.66], respectively); concomitant use of some individual supplements seemed to increase the risk further.

Detection bias is unlikely to have distorted the positive association found between excessive multivitamin use and advanced and fatal prostate cancer. These worrying findings require further assessment.