A Review of the Relationship between Lentil Serving and Acute Postprandial Blood Glucose Response; Effects of Dietary Fibre, Protein and Carbohydrates

Consumption of pulses has been shown to have beneficial effects on blood glucose and insulin levels. Lentils are a dry harvested grain of the legume family containing significant amounts of resistant, slow and rapidly digestible starches, with a range of protein depending on the specific variety. Lentil consumption consistently lowers acute blood glucose and insulin response when compared to starchy control foods. The mechanism by which lentils lower blood glucose and insulin levels after meal consumption is unclear; however, evidence suggests that this effect may be linked to the macronutrient profile and the serving size consumed. This review consolidated published studies that examined the impact of lentil consumption on glycemic and insulin responses, and provided information on the protein, dietary fibre and available carbohydrate content of foods tested. The analyzed studies collectively suggest that consumption of lentils reduces postprandial blood glucose responses (PBGR), with the minimum effective serving size of 110g cooked lentils needed to reduce PBGR by 20%, a value deemed significant by Health Canada guidelines. Reductions in PBGR had modest-to-strong correlations with protein (45–57 g) and dietary fibre (22–30 g) content, and weaker correlations with available carbohydrates. Larger lentil serving sizes were found to moderately influence relative reductions in peak blood glucose concentrations and lower the area under the blood glucose curve (BG AUC), which are important variables in assessing glycemic responses. However, no clear relationship was identified between serving size and relative reductions in the BG AUC, which made it challenging to characterize consistent serving–response effects for lentils.