Dietary protein intake and subsequent risk of type 2 diabetes: a dose-response meta-analysis of prospective cohort studies.
Dietary proteins, including those obtained from animal and plant sources, have inconsistently been correlated with type 2 diabetes mellitus (T2DM) risk. Therefore, a meta-analysis was conducted to evaluate the association between dietary proteins and the risk of T2DM. Prospective cohort studies published until November 2018 were systematically searched in PubMed, Embase, and the Cochrane library. The pooled relative risks (RRs) were calculated with 95% confidence intervals (CIs) using the random-effects model. Ten articles involving a total of 21 cohorts were included in the final meta-analysis. A total of 487,956 individuals were recruited in these studies and 38,350 T2DM cases were reported. Analysis of the pooled RRs indicated that high total protein intake was associated with an increased risk of T2DM (RR 1.10; P = 0.006), whereas moderate total protein intake was not significantly associated with T2DM risk (RR 1.00; P = 0.917). Moreover, a higher risk of T2DM was observed with high animal protein intake (RR 1.13; P = 0.013), whereas moderate animal protein intake had little or no effect on T2DM risk (RR 1.06; P = 0.058). Finally, high intake of plant protein did not affect T2DM risk (RR 0.93; P = 0.074), whereas moderate intake was associated with a reduced risk of T2DM (RR 0.94; P < 0.001). The results of this study indicate that high total protein and animal protein intakes are associated with an increased risk of T2DM, whereas moderate plant protein intake is associated with a decreased risk of T2DM.