Egg consumption and risk of type 2 diabetes: a meta-analysis of prospective studies

Observational data on the association between egg consumption and risk of type 2 diabetes mellitus (DM) have been inconsistent. Because eggs are a good source of protein and micronutrients and are inexpensive, it is important to clarify their role in the risk of developing DM. We conducted a meta-analysis of published prospective cohort studies to evaluate the relation of egg consumption with the risk of DM. We searched PubMed, Ovid, Cochrane, and Google Scholar (up to October 2015) to retrieve published studies. We used RRs from extreme categories of egg consumption for the main analysis but also evaluated dose response by using cubic splines and generalized least squares regression. We identified 12 cohorts for a total of 219,979 subjects and 8911 cases of DM. When comparing the highest with the lowest category of egg intake, pooled multivariate RRs of DM were 1.09 (95% CI: 0.99, 1.20) using the fixed-effect model and 1.06 (95% CI: 0.86, 1.30) using the random-effect model. There was evidence for heterogeneity (I(2) = 73.6%, P < 0.001). When stratified by geographic area, there was a 39% higher risk of DM (95% CI: 21%, 60%) comparing highest with lowest egg consumption in US studies (I(2) = 45.4%, P = 0.089) and no elevated risk of DM with egg intake in non-US studies (RR = 0.89; 95% CI: 0.79, 1.02 using the fixed-effect model, P < 0.001 comparing US with non-US studies). In a dose-response assessment using cubic splines, elevated risk of DM was observed in US studies among people consuming ≥3 eggs/wk but not in non-US studies. Our meta-analysis shows no relation between infrequent egg consumption and DM risk but suggests a modest elevated risk of DM with ≥3 eggs/wk that is restricted to US studies.