Sources of protein in a person's diet may be related to their risk for type 2 diabetes, according to a recent study.
Researchers used data from the Women's Health Initiative (WHI) and the U.K. Biobank to investigate the association between protein intake and development of type 2 diabetes, as well as the potential mediating roles of type 2 diabetes biomarkers. Cox proportional hazard models were used to estimate associations between protein and type 2 diabetes, and mediation analysis was used to assess the roles of biomarkers in case-control studies that were nested in the WHI. One of the study authors reported receiving consulting fees from Solo GI Nutrition and an honorarium from the Soy Nutrition Institute. The results of the study were published June 17 by Diabetes Care.
Overall, 108,681 postmenopausal women without type 2 diabetes at baseline were included from the WHI (primary cohort) and 34,616 adults without type 2 diabetes were included from the U.K. Biobank (replication cohort). A total of 15,842 incident cases of type 2 diabetes were identified in the WHI during a median follow-up of 15.8 years. Animal protein intake was associated with higher risk for type 2 diabetes, while plant protein intake was associated with decreased risk (hazard ratios for highest vs. lowest quintile, 1.31 [95% CI, 1.24 to 1.37] and 0.82 [95% CI, 0.78 to 0.86], respectively). In a replication analysis using data from the 14,902 men and 19,714 women in the U.K. Biobank, 663 incident cases of type 2 diabetes were identified over a median follow-up of 11.4 years. The replication cohort showed similar positive associations of intake of total protein, red meat, processed meat, eggs, and poultry and inverse associations of whole grain intake with risk of incident type 2 diabetes. These findings were materially attenuated after additional adjustment for body-mass index. When 5% of energy intake from plant protein was substituted for animal protein in the WHI, type 2 diabetes risk was estimated to decrease by approximately 21% (hazard ratio, 0.79 [95% CI, 0.74 to 0.84]); this was mediated by levels of high-sensitivity C-reactive protein, interleukin-6, leptin, and sex hormone binding globulin.
The researchers noted that data on diet were self-reported and that residual confounding was possible, among other limitations. They concluded that based on their findings from two large prospective cohorts, intake of animal proteins was associated with higher risk for type 2 diabetes while intake of plant proteins was associated with lower risk.
“Substituting the unfavorable animal protein sources as determined in this study with plant protein sources, milk, yogurt, cheese, or high–n-3 seafood was associated with lower risk of T2D [type 2 diabetes],” the researchers concluded. “The beneficial association of isocaloric substitution of plant protein for animal protein was mechanistically mediated mainly by obesity-related inflammation. These findings support the recommendation that dietary protein sources should be given attention for the prevention of T2D.”