This report reviews published epidemiologic research on the associations of
vitamin and
mineral supplementation with
cancer risk. Although the literature on nutrition and
cancer is vast, few reports to date have addressed supplemental nutrients directly (seven clinical trials, 16 cohort, and 36 case-control studies). These studies offer insight into effects of nutrients that are distinguishable from effects of other biologically active compounds in foods. Randomized clinical trials have not shown significant protective effects of
beta-carotene, but have found protective effects of:
alpha-tocopherol against
prostate cancer; mixtures of
retinol/
zinc and
beta-carotene/
alpha-tocopherol/
selenium against
stomach cancer; and
selenium against total, lung, and
prostate cancers. Cohort studies provide little evidence that
vitamin supplements are associated with
cancer. Case-control studies have reported an inverse association between
bladder cancer and
vitamin C; oral/
pharyngeal cancer and several supplemental
vitamins; and several
cancers and
vitamin E. A randomized clinical trial, a cohort study, and a case-control study have all found inverse associations between
colon cancer and
vitamin E. Overall, there is modest evidence for protective effects of nutrients from supplements against several
cancers. Future studies of supplement use and
cancer appear warranted; however, methodologic problems that impair ability to assess supplement use and statistical modeling of the relation between
cancer risk and supplement use need attention.