Glycaemic response to varying the proportions of starchy foods and non-starchy vegetables within a meal: A randomised controlled trial

Background: Glycaemic response is an important contributor to glycaemic control and is positively associated with the risk of developing diabetic complications. As it is largely determined by the type and amount of carbohydrate consumed, manipulating carbohydrate intake may have the potential to modify glycaemic response. Current guidelines recommend that one quarter of your plate contains starchy carbohydrate foods, one quarter protein based foods and the remaining half non-starchy vegetables. It is unsure to what extent altering the proportions of starchy foods and non-starchy vegetables within a meal will affect glycaemic response. Objective: To examine the effect on glycaemic response in non-diabetic people of varying the proportions of a starchy carbohydrate food and non-starchy vegetables within a meal. Design: Randomised controlled crossover trial Methods: Over three separate testing days 74 healthy young adults consumed three test meals with varying proportions of starchy carbohydrate foods (30g, 45g, 60g available carbohydrate from either pasta or rice) and non-starchy vegetables. A gram for gram substitution of pasta or rice for non-starchy vegetables was used so as the total weight of each meal remained the same. Participants were randomised to receive either three pasta-based meals or three rice-based meals. Postprandial glycaemic response was measured by finger prick blood samples over a 90-minute period following the consumption of each test meal. Results: Glycaemic response, measured by incremental area under the curve (iAUC) glucose, and 90-minute blood glucose concentration increased as the proportion of pasta or rice within the meal increased and the proportion of non-starchy vegetables decreased (p<0.001 and p<0.01, respectively). Mean iAUC for the pasta-based meals with the small (30g available carbohydrate) and medium (45g available carbohydrate) amount of carbohydrate was 92.9 (43.3) mmol*min/L and 117.6 (SD: 43.3) mmol*min/L, respectively and there was a difference between them (p=0.002). iAUC for the pasta-based meal with the large amount of carbohydrate (60g available carbohydrate) was 122.2 (55.1) mmol*min/L however there was no difference between the medium and large meals (p=0.573). For the rice-based meals mean iAUC was 128.6 (78.1) mmol*min/L, 140.1 (77.6) mmol*min/L and 196.9 (82.4) mmol*min/L for the small, medium and large meals, respectively. There was no difference in iAUC between the medium and small meals (p=0.314) however there was a difference between the medium and large meals (p<0.001). Rice-based meals induced 16-46% larger glycaemic responses than the pasta-based meals with there being a difference for the small and large meals (p=0.048 and p