Metabolic Responses to Native Wheat Starch (Midsol(TM) 50) versus Resistant Wheat Starch Type 4 (Fibersym(®) RW): Standard versus Marketplace Testing Protocols

BACKGROUND: To investigate the effect of resistant starch (RS) on acute glycemic or insulinemic responses, the FDA indicates that control and RS-enriched foods must contain equivalent amounts of digestible carbohydrate. However, RS-containing foods typically contain less digestible carbohydrate per serving than control foods. Thus, controlling for digestible carbohydrate may yield different responses as compared with controlling for serving size. OBJECTIVE: The aim was to compare the postprandial metabolic responses to native wheat starch (NWS) versus RS type 4 (RS4) using digestible carbohydrate–matched portions compared with weight-matched portions. METHODS: A single-blind, randomized-controlled crossover trial examined glycemic and insulinemic responses over 2 h following consumption of 4 cracker conditions and a dextrose beverage in apparently healthy participants (n = 14). Crackers provided 50 g of digestible carbohydrate using the FDA's meal-intervention protocol or 35 g of carbohydrate by weight for the marketplace substitution method. Crackers differed only by the type of starch additive: NWS (Midsol(TM) 50; MGP Ingredient, Inc.) or RS4 (Fibersym(®) RW; MGP Ingredients, Inc.). Glucose concentrations were assessed at baseline and at 15, 30, 45, 60, 90, and 120 min; insulin concentrations were measured at baseline and 30, 60, and 120 min. RESULTS: There were no significant differences between 50 g digestible carbohydrate cracker conditions for glucose or insulin incremental AUC (iAUC). The 35 g carbohydrate by weight conditions were not different for glucose iAUC [mean (95% CI): 35 g NWS: 1317 (677, 2169); 35 g RS4: 701 (262, 1351); P > 0.05]. However, insulin iAUC was lower following 35 g RS4 compared with 35 g NWS [35 g RS4: 92 (1, 259); 35 g NWS: 697 (397, 1080); P < 0.01]. CONCLUSIONS: In healthy adults, consumption of RS4 crackers decreased postprandial insulin responses compared with NWS crackers when using the marketplace substitution method compared with the FDA standard testing method, with similar postprandial glucose responses. Comparisons of the FDA standard testing method and the marketplace substitution method should be investigated further to elucidate differential physiological impacts on consumers.