A word of caution against excessive protein intake
Bettina Mittendorfer , Samuel Klein and Luigi Fontana
Mittendorfer, B., Klein, S., & Fontana, L. (2019). A word of caution against excessive protein intake. Nature Reviews Endocrinology. doi:10.1038/s41574-019-0274-7
Abstract
Dietary protein is crucial for human health because it provides essential amino acids for protein synthesis. In addition, dietary protein is more satiating than carbohydrate and fat. Accordingly, many people consider the protein content when purchasing food and beverages and report ‘trying to eat more protein’. The global market for protein ingredients is projected to reach approximately US$90 billion by 2021, largely driven by the growing demand for protein-fortified food products. This Perspective serves as a caution against the trend of protein- enriched diets and provides an evidence-based counterpoint that underscores the potential adverse public health consequences of high protein intake.
Conclusions
The results from both population and randomized experimental diet intervention studies conducted in people do not support the popular trend in the general population of increasing dietary protein intake beyond the RDI to increase muscle mass, overall physical function and glucose homeostasis. Although high dietary protein intake can increase muscle mass during resistance exercise training in young adults, a high-protein diet does not have clinically meaningful effects on lean mass or muscle mass during weight maintenance, weight gain or weight loss. Moreover, increasing protein intake is not without risk and can have adverse effects on metabolic function (Fig. 3).
The stimulation of glucagon and insulin secretion and impairment of insulin action that occurs immediately after protein ingestion provides a potential mechanistic link between high protein intake and the increased risk of prediabetes and T2DM observed in population studies. In addition, in people with overweight and obesity, high protein intake without a concomitant substantial decrease in carbohydrate intake attenuates the therapeutic effect of diet-induced weight loss on whole-body insulin sensitivity. However, increased protein intake and consequent glucagon secretion could be beneficial in people with obesity and T2DM by facilitating weight loss and improving glycaemic control through an increase in satiety and the thermic effect of feeding, slower gastric emptying, decreased and slower glucose appearance in plasma and enhanced insulin secretion1–3,99,102,115.
