Emerging Evidence for the Importance of Dietary Protein Source on Glucoregulatory Markers and Type 2 Diabetes: Different Effects of Dairy, Meat, Fish, Egg, and Plant Protein Foods

Observational studies provide evidence that a higher intake of protein from plant-based foods and certain animal-based foods is associated with a lower risk for type 2 diabetes (T2DM). However, there are few distinguishable differences between the glucoregulatory qualities of the proteins in plant-based foods, and it is likely their numerous non-protein components (e.g., fibers and phytochemicals) that drive the relationship with T2DM risk reduction. Conversely, the glucoregulatory qualities of the proteins in animal-based foods are extremely divergent, with a higher intake of certain animal-based protein foods showing negative effects, and others showing neutral or positive effects on T2DM risk. Among the various types of animal-based protein foods, a higher intake of dairy products (such as milk, yogurt, cheese and whey protein) consistently shows a beneficial relationship with glucose regulation and/or T2DM risk reduction. Intervention studies provide evidence that dairy proteins have more potent effects on insulin and incretin secretion compared to other commonly consumed animal proteins. In addition to their protein components, such as insulinogenic amino acids and bioactive peptides, dairy products also contain a food matrix rich in calcium, magnesium, potassium, trans-palmitoleic fatty acids, and low-glycemic index sugars—all of which have been shown to have beneficial effects on aspects of glucose control, insulin secretion, insulin sensitivity and/or T2DM risk. Furthermore, fermentation and fortification of dairy products with probiotics and vitamin D may improve a dairy product’s glucoregulatory effects.