Reducing the postprandial glycaemic impact of dietary protein in type 1 diabetes mellitus

Type 1 diabetes is a serious, life-long, autoimmune condition that occurs predominantly during childhood and adolescence. It is well recognised that intensive insulin therapy is the optimal method of managing type 1 diabetes. This approach has been demonstrated to reduce the risk of long-term complications of diabetes by reducing glycaemic variability and HbA1c. Despite the increased use of intensive insulin therapy, postprandial glycaemic excursions remain a significant challenge for many people living with type 1 diabetes. This is important as postprandial hyperglycaemia has been identified as an independent risk factor for the development of long-term complications of type 1 diabetes, often despite careful pre-meal insulin dosing and in-target HbA1c. A key component of intensive insulin therapy is matching meal-time insulin doses to the carbohydrate content of a meal, together with the pre-prandial blood glucose level. This is based on the assumption that carbohydrates are the main macronutrient to influence postprandial glycaemia. However, there is increasing evidence that other macronutrients – protein and fat – can also have a significant impact on postprandial glycaemia. The primary purpose of this thesis is to investigate the postprandial glycaemic effects and subsequent insulin requirements of dietary protein. A systematic review of the literature revealed that dietary protein can cause significant delayed and sustained postprandial hyperglycaemia and increased insulin requirements in individuals with type 1 diabetes. This review has highlighted that gaps in the literature exist regarding how dietary protein impacts postprandial glycaemia in type 1 diabetes and that strategies to reduce glycaemic excursions following high-protein meals are needed. Overall, the sequence of studies presented in this thesis have sought to gain an improved understanding of the glycaemic effects of dietary protein, in order to improve the effectiveness of meal-time insulin dosing strategies and reduce the risk of postprandial hyperglycaemia. The clinical implications of the findings of the studies conducted are presented, with practical recommendations described for the management of high-protein meals with the aim of improving long-term outcomes for people living with type 1 diabetes.