Calcium, dairy foods, and risk of incident and fatal prostate cancer

Calcium and dairy foods in relation to prostate cancer were examined in the National Institutes of Health (NIH)-AARP (formerly known as the American Association of Retired Persons) Diet and Health Study (1995/1996-2001). Diet was assessed with a food frequency questionnaire at baseline. Multivariate relative risks and 95% confidence intervals were estimated by Cox regression. During up to 6 years of follow-up (n = 293,888), the authors identified 10,180 total prostate cancer cases (8,754 nonadvanced, 1,426 advanced, and 178 fatal cases). Total and supplemental calcium were unrelated to total and nonadvanced prostate cancer. However, a statistically nonsignificant positive association with total calcium was observed for advanced (≥2,000 vs. 500-<750 mg/day: relative risk (RR) = 1.25, 95% confidence interval (CI): 0.91, 1.71; p_trend = 0.06) and fatal (≥1,000 vs. 500-<750 mg/day: RR = 1.39, 95% CI: 0.92, 2.09; p_trend = 0.10) prostate cancer. Skim milk, but not other dairy foods, was associated with increased risk of advanced prostate cancer (≥2 vs. zero servings/day: RR = 1.23, 95% CI: 0.99, 1.54; p_trend = 0.01). In contrast, calcium from nondairy foods was associated with lower risk of nonadvanced prostate cancer (≥600 vs. <250 mg/day: RR = 0.82, 95% CI: 0.68, 0.99; p_trend = 0.04). Although the authors cannot definitively rule out a weak association for aggressive prostate cancer, their findings do not provide strong support for the hypothesis that calcium and dairy foods increase prostate cancer risk.