Estimated intake of preformed vitamin A from all evaluated foods and supplements showed no trend or monotonic decrease in risk across categories of intake. These data do not allow us to distinguish among several potential explanations for the protective association observed between intake of carrots and spinach and risk of breast cancer. The findings are, however, consistent with a diet rich in these foods having a modest protective effect. This report reviews published epidemiologic research on the associations of vitamin and mineral supplementation with cancer risk. These studies offer insight into effects of nutrients that are distinguishable from effects of other biologically active compounds in foods.
Cohort studies provide little evidence that vitamin supplements are associated with cancer.
Tsubono Y, Okubo S, Hayashi M, Kakizoe T, Tsugane S Epidemiology and Biostatistics Division, National Cancer Center Research Institute, Kashiwa. The subjects were participants in an annual health screening program conducted by four municipalities in Akita prefecture, one of the regions with the highest mortality from gastric cancer in Japan. The results indicate that a randomized controlled trial for cancer prevention is feasible in the Japanese asymptomatic population. In addition, all patients received a multivitamin supplement. Body weights and Karnofsky scores were evaluated at each visit.