Dairy products, calcium and prostate cancer risk

Prospective cohort within the Harvard Alumni Health Study; male alumni; mean baseline age 67 years; 12,805 eligible in 1988; after excluding baseline cancers (n=1,731) and those with missing dairy intake data (n=60), 11,014 remained; 10,011 followed for incident prostate cancer through 1998 (815 cases; 99 fatal). Diet assessed in 1988 via a semi-quantitative food-frequency questionnaire focusing on seven dairy products; calcium intake estimated from dairy items; information on calcium supplements and potential confounders collected. Prostate cancer cases identified by self-reports on follow-up questionnaires (validated by attending physicians in 91% of cases) and death certificates for fatal cases; Cox proportional hazards models with multivariate adjustment for age, BMI, physical activity, smoking, total energy, alcohol, red meat, vegetables, and paternal history of prostate cancer.

No significant associations between higher intakes of dairy products, calcium from dairy, or calcium supplements and prostate cancer risk, or fatal prostate cancer. Highest dairy intake showed multivariate RR 1.11 (95% CI 0.85–1.46); calcium intake and supplement use showed no significant trends. Conclusion: higher calcium intake from dairy or supplements does not increase prostate cancer risk in this cohort; calcium remains important for bone health, but findings may not generalize to other populations; further research in diverse populations is warranted.

Calcium intake may have been too low to detect an effect; reliance on self-reported dietary data with potential misclassification; lack of information on cancer stage/grade; possible residual confounding; generalizability limited to older men.