The Glycemic Impact of Protein Ingestion in People With Type 1 Diabetes

In individuals with type 1 diabetes, carbohydrate is commonly recognized as the primary macronutrient influencing postprandial glucose levels. Accumulating evidence indicates that protein ingestion also contributes to the increment in postprandial glucose levels, despite endocrine and metabolic responses different from those with carbohydrate ingestion. However, findings regarding protein ingestion’s glycemic effect in people with type 1 diabetes are equivocal, with the magnitude of glycemic response seemingly dependent on the rate of absorption and composition of protein ingested. Therefore, the aim of this article is to outline the physiological mechanisms by which ingested protein influences blood glucose regulation in individuals with type 1 diabetes and provide clinical implications on use of dietary protein in the context of glycemic management. Specifically, protein ingestion raises plasma amino acid levels, which directly or indirectly (via gut hormones) stimulates glucagon secretion. Together with the increase in gluconeogenic precursors and an absent endogenous insulin response in individuals with type 1 diabetes, this provides a synergistic physiological environment for increased endogenous glucose production and subsequently increasing circulating glucose levels for several hours. While there is a dearth of well-controlled studies in this area, we provide clinical implications and directions for future research regarding the potential for using ingestion of fast-absorbing protein (such as whey protein) as a tool to prevent and mitigate overnight- and exercise-induced hypoglycemia in people with type 1 diabetes.