Dietary beta-carotene, vitamin C, and risk of prostate cancer: results from the Western Electric Study.

Dietary factors are likely candidates for important determinants of prostatic cancer risk. Among the most investigated nutritional factors have been antioxidants. We evaluated dietary beta-carotene and vitamin C in relation to subsequent risk of prostate cancer in a prospective study of 1,899 middle-aged men. We combined prostate cancer cases diagnosed in the first 24 years of follow-up with incident cases identified from the Health Care Financing Administration hospitalization and outpatient files during an additional 6-year follow-up period. We obtained death certificates for all decedents. During the 30-year follow-up, prostate cancer developed in 132 men. There was no indication that consumption of beta-carotene or vitamin C was related to increased or decreased risk of prostate cancer. Relative risks for highest vs lowest quartiles of beta-carotene and vitamin C intake were 1.27 [95% confidence interval (CI) = 0.75-2.14] and 1.03 (95% CI = 0.59-1.60), respectively, after adjustment for age, number of cigarettes smoked per day, dietary cholesterol and saturated fat, alcohol consumption, total energy intake, and occupation. Associations between intake of these nutrients and risk of prostate cancer differed depending on whether the cancer was diagnosed during the first 19 years of follow-up or the next 11 years of follow-up. Overall survival over the 30 years of follow-up was positively associated with intake of beta-carotene and vitamin C.