Mycoprotein is a high protein, high fibre, fungal-derived food ingredient that has been previously shown to reduce postprandial glucose concentrations in young healthy adults. The reduction of postprandial glucose concentrations could be beneficial in the dietary management of impaired glycaemic control and type 2 diabetes (T2D). However, it is unclear how this reduction with mycoprotein occurs mechanistically, and whether an improvement in overall glycaemic control would occur after habitual consumption of mycoprotein in people with T2D.
The aim of the present thesis was to explore the role of mycoprotein in glycaemic control, both acutely and after 5-weeks of habitual consumption, across a spectrum of glucose tolerance, using a comprehensive assessment of postprandial glucose kinetics and insulin sensitivity. Firstly, the role of mycoprotein in acute glycaemic control was explored by applying a dual stable isotope glucose tracer method over a 6-hour postprandial period to determine how the co-ingestion of 20 or 40g of freeze-dried mycoprotein with 50g dextrose and 250ml milk, impacted the rate of appearance (RaT) and disappearance (RdT) of glucose in young healthy adults, compared to an energy and macronutrient matched control (75g carbohydrate, 18g protein and 12g fat). Secondly, this method was applied to adults with hyperinsulinaemic obesity, to determine how mycoprotein impacted postprandial glucose kinetics in people with impaired glycaemic control. Finally, the impact of regular consumption of mycoprotein, as part of 5-week high-protein, controlled vegan diet, was assessed in people with T2D using a comprehensive assessment of glycaemic control including a mixed-meal tolerance test, hyperinsulinaemic-euglycaemic clamp with stable isotope glucose tracers and continuous glucose monitoring. These assessments provided measures of glucose tolerance and β-cell function, hepatic and peripheral insulin sensitivity, and glycaemic variability, respectively.
The studies presented in this thesis demonstrate that mycoprotein does not lower acute postprandial glucose concentrations, contrary to previous findings. In young healthy adults 20g mycoprotein increased blood glucose, serum insulin and RdT after co-ingestion with glucose, compared to an energy and macronutrient matched control drink. However, in people with obesity there was no difference in postprandial glycaemic control after mycoprotein and a control drink. The co-ingestion of freeze-dried mycoprotein with dextrose did not impact the exogenous appearance of glucose, or the endogenous glucose production over a 6h postprandial period in healthy adults, and adults with obesity. A primary novel finding of this thesis was that the incorporation of mycoprotein into a high-protein vegan diet was associated with reduced glycaemic variability, HbA1c and peripheral insulin sensitivity to a similar extent as a high protein animal-based protein diet, in people with T2D. The findings from this thesis may have important clinical and practical implications. This thesis demonstrates that the incorporation of mycoprotein into a habitual vegan can be safe and potentially beneficial for those with T2D, thus increasing the dietary options available for both patients and clinicians/ dietitians that are advising the dietary management of T2D.
This thesis details a unique and novel body of work characterising the effect of mycoprotein on both acute and longer-term glycaemic control, across a spectrum of glucose tolerance.