Dietary protein intake and risk of type 2 diabetes: a dose-response meta-analysis of prospective studies

PurposeThe association between dietary protein intake and type 2 diabetes risk has been inconsistent in the previous epidemiological studies. We aimed to quantitatively assess whether dietary total, animal, and plant protein would be associated with type 2 diabetes risk.MethodsA comprehensive literature review was conducted to identify related articles by searching PubMed, Embase, Web of Science, and Wiley Online Library through 20th March 2018. Generalized least squares for trend estimation and restricted cubic spline regression model were applied in the dose-response analysis.ResultsEight publications with ten prospective cohorts of 34,221 type 2 diabetes cases were included. After adjustment of potential confounders, a 5% of energy increment from dietary total and animal protein intake was related to a 9% (1.04, 1.13; I-2=42.0%) and 12% (95% CI 1.08, 1.17; I-2=14.0%) higher risk of type 2 diabetes respectively. However, for plant protein, a significant U-shaped curve was observed with the most risk reduction at intake of about 6% of energy intake from plant protein intake (P-nonlinearity=0.001). The results were robust in sensitivity analysis and no publication bias was detected.ConclusionsThese findings indicate that the consumption of protein particularly animal protein may be associated with an increased risk of type 2 diabetes.