Epidemiological studies show correlations between risk factors for prostate cancer and conditions that can result in decreased vitamin D levels (57). Increased age is associated with an increased risk of prostate cancer, as well as with decreased sun exposure and decreased capacity to synthesize vitamin D. The incidence of prostate cancer is higher in African American men than in white American men, and the high melanin content of dark skin is known to reduce the efficiency of vitamin D synthesis. Geographically, mortality from prostate cancer is inversely associated with the availability of sunlight. Findings that prostate cells in culture can synthesize the 25-hydroxyvitamin D3-1-hydroxylase enzyme and that, unlike the renal enzyme, its synthesis is not influenced by PTH or calcium levels also provide support for the idea that increasing 25-hydroxyvitamin D levels may be useful in preventing prostate cancer (76). In contrast, prospective studies have not generally found significant relationships between serum 25-hydroxyvitamin D levels and subsequent risk of developing prostate cancer (77-80). Although a prospective study of Finnish men found that low serum 25-hydroxyvitamin D levels were associated with earlier and more aggressive prostate cancer development (81), another prospective study of men from Finland, Norway and Sweden found a U-shaped relationship between serum 25-hydroxyvitamin D levels and prostate cancer risk. In that study serum 25-hydroxyvitamin D concentrations of 19 nmol/L or lower and 80 nmol/L or higher were associated with higher prostate cancer risk (82). Further research is needed to determine the nature of the relationship between vitamin D nutritional status and prostate cancer risk.