Postprandial hyperglycemia in patients with type 2 diabetes is reduced by raw insoluble fiber: A randomized trial

Abstract

Background and aimsA lower risk of type 2 diabetes mellitus (T2DM) is associated with the intake of insoluble fiber. This contradicts the postulate that insoluble fibers do not decrease postprandial glycemic response and that only viscous gel-forming soluble fibers would do this. This study aimed to investigate the effect of a dose of insoluble fibers that meets dietary recommendations on postprandial hyperglycemia in T2DM patients. Methods and resultsThis is a randomized crossover clinical trial. Nineteen T2DM men randomly ate a balanced breakfast either without (Control) or with prior consumption of insoluble fibers (5.8 g) in the form of 15 g of raw wheat bran (RWB). Glycemia was measured at fasting and 15, 30, 45, 60, 90, and 120 min postprandially. Markers of taste intensity and palatability were assessed after breakfast intake. The glucose peak rise of 87 mg/dL and the incremental area under the curve (AUC) elicited by the breakfast were decreased by RWB (15.80 % and 23.14 %, respectively). Time-to-glucose-peak did not differ between groups. The addition of the RWB to the meal decreased its level of creaminess and tasty and increased the sourness and bitterness. ConclusionsThe postprandial hyperglycemia in T2DM patients in response to complex carbohydrates was decreased by prior intake of a recommended dose of raw insoluble fibers. This antihyperglycemic effect is in accordance with the acarbose-like property of raw insoluble fibres, but not of heated ones (e.g., bread and pasta), to inhibit the activities of the carbohydrate-digesting enzymes alpha-glucosidase/alpha-amylase. Registration number for clinical trialsRBR-98tx28b (https://ensaiosclinicos.gov.br/rg/RBR-98tx28b).