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Dairy products, calcium, and prostate cancer risk: a systematic review and meta-analysis of cohort studies

Publication: Am J Clin Nutr., Volume 101, Issue 1, January 2015, Pages 87-117

Background:
Dairy product and calcium intakes have been associated with increased prostate cancer risk, but whether specific dairy products or calcium sources are associated with risk is unclear.

Objective:
In the Continuous Update Project, we conducted a meta-analysis of prospective studies on intakes of dairy products and calcium and prostate cancer risk.

Design:
PubMed and several other databases were searched up to April 2013. Summary RRs were estimated by using a random-effects model.

Results:
Thirty-two studies were included. Intakes of total dairy products [summary RR: 1.07 (95% CI: 1.02, 1.12; n = 15) per 400 g/d], total milk [summary RR: 1.03 (95% CI: 1.00, 1.07; n = 14) per 200 g/d], low-fat milk [summary RR: 1.06 (95% CI: 1.01, 1.11; n = 6) per 200 g/d], cheese [summary RR: 1.09 (95% CI: 1.02, 1.18; n = 11) per 50 g/d], and dietary calcium [summary RR: 1.05 (95% CI: 1.02, 1.09; n = 15) per 400 mg/d] were associated with increased total prostate cancer risk. Total calcium and dairy calcium intakes, but not nondairy calcium or supplemental calcium intakes, were also positively associated with total prostate cancer risk. Supplemental calcium was associated with increased risk of fatal prostate cancer.

Conclusions:
High intakes of dairy products, milk, low-fat milk, cheese, and total, dietary, and dairy calcium, but not supplemental or nondairy calcium, may increase total prostate cancer risk. The diverging results for types of dairy products and sources of calcium suggest that other components of dairy rather than fat and calcium may increase prostate cancer risk. Any additional studies should report detailed results for subtypes of prostate cancer.

Commented by Henk van der Poel

In this meta-analysis on 32 studies, dairy products and calcium intake increased the risk of prostate cancer 3-7%. In line with an earlier meta-analysis (Bristow et al., Br J Nutr. 2013 Oct;110(8):1384-93) the use of supplemental nondairy calcium was not found to increase the incidence of prostate cancer but did increase the risk of fatal prostate cancer – an interesting observation. Whether the fact that it took more than one year for the manuscript to be accepted for publication reflects the complexity and therefore the applicability of the results remains to be determined.