Dietary protein intake and risk of type 2 diabetes: results from the Melbourne Collaborative Cohort Study and a meta-analysis of prospective studies

Abstract

Background: Reported associations between protein intake from different sources and type 2 diabetes (T2D) have been inconsistent. Objective: We prospectively examined the relations of total, animal, and plant protein intakes with incident T2D. Design: We followed 21,523 participants (women: 61.7%) between 1990 and 2007 from the Melbourne Collaborative Cohort Study who were free of diabetes, cardiovascular disease, cancer, and kidney stones at baseline. We also conducted a meta-analysis that included the results from our cohort and from 10 previous prospective studies. Results: A total of 929 new cases (4.3%) of T2D were documented during a mean of 11.7 y of follow-up. Multivariate-adjusted ORs for incident T2D in the highest compared with lowest quintiles of total and animal protein intakes as percentages of energy were 1.23 (95% CI: 0.96, 1.56; P-trend = 0.029) and 1.29 (95% CI: 0.99, 1.67; P-trend = 0.014), respectively. These associations appeared to be greater in men and in participants with normal baseline plasma glucose, body mass index, or blood pressure. Plant protein intake was inversely associated with incident T2D in women only (OR; 0.60; 95% CI: 0.37, 0.99). In the meta-analysis of 11 prospective cohort studies with 505,624 participants and 37,918 T2D cases (follow-up range: 5-24 y), pooled RRs for the comparison of the highest with lowest categories of total, animal, and plant protein intakes were 1.09 (95% CI: 1.06, 1.13), 1.19 (95% CI: 1.11, 1.28), and 0.95 (95% CI: 0.89, 1.02), respectively. Associations between animal protein intake and T2D were similar across sex, geographic region, length of follow-up, study quality, and method of expressing protein intake. An inverse association between plant protein intake and T2D was observed in women (RR: 0.93; 95% CI: 0.85, 1.00) and in US populations (RR: 0.91; 95% CI: 0.84, 0.97). Conclusion: Higher intakes of total and animal protein were both associated with increased risks of T2D, whereas higher plant protein intake tended to be associated with lower risk of T2D.Am J Clin Nutr 2016;104:1352-65.

Comparison of the effects of diets high in animal or plant protein on metabolic and cardiovascular markers in type 2 diabetes: A randomized clinical trial

“…The PP diets were shown to reduce the incidence of T2DM and cardiovascular disease, while AP diets increased such incidences. [5][6][7][8]38 Unexpectedly, the present data showed a similar improvement in glycaemic and metabolic control in both dietary groups. Although the metabolic improvement might have been attributable to the dietary intervention and moderate weight loss per se, the absence of major differences between the AP and PP groups indicates that the protein composition did not affect the response to the intervention.…”

“…The PP diets were shown to reduce the incidence of T2DM and cardiovascular disease, while AP diets increased such incidences . Unexpectedly, the present data showed a similar improvement in glycaemic and metabolic control in both dietary groups.…”

“…The present study therefore supports the use of high AP or PP diets in the short term. In view of the unfavourable results with AP as compared to PP in epidemiological studies, [4][5][6][7][8]11,50 explanations targeting differences in behaviour, phytochemical content, carbohydrate and fat quality or other confounders might deserve attention.…”

High Protein Diet and Metabolic Plasticity in Non-Alcoholic Fatty Liver Disease: Myths and Truths

“…In the last few years many studies started to questioning the effects of animal (e.g., meat and dairy products) and plant (e.g., grains and legumes) proteins intake on risk to develop cardiovascular disease and cancer [112,113]. In a recent meta-analysis proteins intake from plants is associated with a decrease risk of diabetes, whereas animal proteins with an increase of it [114,115].…”

Associations of nutrient intakes with obesity and diabetes mellitus in the longitudinal medical surveys of Japanese Americans

“…The present study also confirmed that higher intakes of total protein, animal protein, animal fat and SFA were only significantly associated with the development of diabetes mellitus in the obese group. Similarly, total protein and animal protein intake are risk factors for the development of diabetes mellitus, based on the findings of European and American studies, as well as a meta‐analysis. It is possible that amino acids reduce the endocrine function of the pancreas, act as gluconeogenic precursors in the liver and increase insulin resistance through the hexosamine biosynthetic pathway.…”