Dairy products and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of cohort studies.

BACKGROUND The association between intake of dairy products and the risk of type 2 diabetes has been investigated in several studies, but the evidence is not conclusive. OBJECTIVE We conducted an updated systematic review and dose-response meta-analysis of dairy product intake and the risk of type 2 diabetes. DESIGN We searched the PubMed database for prospective cohort and nested case-control studies of dairy product intake and risk of type 2 diabetes up to 5 June 2013. Summary RRs were estimated by use of a random-effects model. RESULTS Seventeen cohort studies were included in the meta-analysis. In the dose-response analysis, the summary RRs (95% CIs) were 0.93 (0.87, 0.99; I(2) = 33%) per 400 g total dairy products/d (n = 12), 0.98 (0.94, 1.03; I(2) = 8%) per 200 g high-fat dairy products/d (n = 9), 0.91 (0.86, 0.96; I(2) = 40%) per 200 g low-fat dairy products/d (n = 9), 0.87 (0.72, 1.04; I(2) = 94%) per 200 g milk/d (n = 7), 0.92 (0.86, 0.99; I(2) = 0%) per 50 g cheese/d (n = 8), and 0.78 (0.60, 1.02; I(2) = 70%) per 200 g yogurt/d (n = 7). Nonlinear inverse associations were observed for total dairy products (P-nonlinearity < 0.0001), low-fat dairy products (P-nonlinearity = 0.06), cheese (P-nonlinearity = 0.05), and yogurt (P-nonlinearity = 0.004), and there was a flattening of the curve at higher intakes. CONCLUSIONS This meta-analysis suggests that there is a significant inverse association between intakes of dairy products, low-fat dairy products, and cheese and risk of type 2 diabetes. Any additional studies should assess the association between other specific types of dairy products and the risk of type 2 diabetes and adjust for more confounding factors.