Background/objectives: Although vitamin D has been experimentally reported to inhibit tumorigenesis, cell growth and prostate cancer invasion, epidemiologic data regarding prostate cancer risk are inconsistent, and some studies have suggested positive but nonsignificant associations. Further, the impact of vitamin D on prostate cancer between Western and Japanese populations may differ due to different plasma vitamin D levels.
Subjects/methods: We performed a nested case-control study within the Japan Public Health Center-based Prospective (JPHC) Study in 14,203 men (40-69 years) who answered a self-administered questionnaire at baseline (1990-1994) and gave blood samples, and were followed until 2005. We identified 201 prostate cancers which are newly diagnosed during follow-up (mean 12.8 years). We selected two matched controls for each case from the cohort. We used a conditional logistic regression model to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) for prostate cancer with respect to levels of 25-hydroxy vitamin D (25(OH)D) in plasma.
Results: We did not observe statistically significant association between 25(OH)D level and total prostate cancer (multivariate OR=1.13 (95%CI=0.66-1.94, Ptrend=0.94) for the highest versus lowest tertile) However, 25(OH) levels were slightly positively associated with advanced cancer. The results remained substantially unchanged after stratification by intake of fish or calcium intake.
Conclusions: 25(OH)D level showed no association with overall prostate cancer among Japanese men in this large cohort.