Milk and Dairy Product Consumption and Prostate Cancer Risk and Mortality: An Overview of Systematic Reviews and Meta-analyses.

Milk and dairy product consumption has been associated with an increase in prostate cancer risk; however, discrepancies have been observed in the literature. This first overview of systematic reviews and meta-analyses was carried out with the main objective of compiling and discussing the evidence generated to date related to milk and dairy product consumption and prostate cancer risk and mortality. A systematic search in MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and the Web of Science (from inception to 30 April 2018) was conducted. The inclusion criteria were as follows: adult men, meta-analyses of longitudinal studies, dairy product consumption, and risk of prostate cancer or related outcomes. The AMSTAR2 checklist was used to evaluate methodological quality. The synthesis methods included dairy product exposure (high compared with low consumption or dose-response), dairy product type (total dairy products, milk, cheese, yogurt, and others), and prostate cancer outcomes (total, nonadvanced, and advanced prostate cancer and mortality) displayed in forest plots. Six meta-analyses were identified. These studies reported on the analysis of the 2 to 32 cohorts (up to 848,395 subjects/38,107 cases; 4-28 y of follow-up) and 2 case-control meta-analyses (12,435 subjects). The meta-analysis quality was valued as mostly "good" according to the AMSTAR2 criteria. All RRs of high compared with low consumption (dose-response) for total prostate cancer ranged from 1.68 to 1.09 (1.07 per 400 g/d) for total dairy products, 1.50 to 0.92 (1.06 to 0.98 per 200 g/d) for milk (whole, low-fat, and skim milk considered separately), and 1.18 to 0.74 (1.10 per 50 g/d) for cheese. RRs have decreased since the first meta-analysis. Statistical heterogeneity generates uncertainty in the observed results (up to I2 = 77.1%). In conclusion, although there are some data indicating that higher consumption of dairy products could increase the risk of prostate cancer, the evidence is not consistent. This review was registered with PROSPERO as CRD42018094737.