The Effect of Lentils on Postprandial Glycemic Response in Healthy Adults and the Ability of In Vitro Digestion to Predict Glycemic Response
Diets rich in carbohydrates that have a low glycemic index (GI) are inversely associated with type 2 diabetes (T2D) risk (Ley et al. 2016) due to the favourable postprandial glycemic response (PPGR). Whether substituting pulses, such as lentils, for a portion of a different starchy foods improves PPGR is unknown. The objectives of this research were: 1) to determine the effects on PPGR of consuming rice or potato alone or in combination with lentils, 2) to determine the effects on PPGR of consuming lentil-based food products compared to the same (control) foods prepared with high-GI starches, and 3) to relate the composition of lentil starch to in vivo PPGR and in vitro digestion variables. For objective #1, healthy adults completed a randomized, crossover clinical trial in which acute glycemic response was examined following consumption of rice (n=24) or potato (n=24) alone or in combination with one of three lentil varieties (large green, small green or split red). Blood glucose incremental area under the curve (iAUC) and maximum concentration (CMAX) were significantly lower following the small green and split red lentil treatments compared to the rice control and for all lentil treatments compared to potato control. For objective #2, healthy adults completed a randomized, crossover clinical trial in which acute glycemic response was examined following consumption of food products (muffin, n=24; chili, n=24; soup, n=20) that contained one of two different lentil varieties (small green or split red) or a commonly consumed starch source (wheat, rice or potato). Blood glucose iAUC and CMAX were significantly lower following lentil-containing chilies and soups compared to controls, while only the blood glucose iAUC for red lentil muffins was significantly lower compared to the control. Finally, the data from these trials was used in combination with in vitro data to explore relationships and discover if in vitro measurements could predict in vivo PPGR. Although more methodological consistency was required to produce reliable relationships, in vitro measurements were strongly correlated with in vivo glycemic and insulinemic responses. These results support the consumption of lentils to attenuate postprandial glycemia.