Resistant Starch Bagels Reduce Fasting and Postprandial Insulin in Adults at Risk of Type 2 Diabetes

Background: Type 2 diabetes (T2D) incidence continues to rise. Although increasing dietary fiber intake is an established strategy for improved glycemic control, most adults consume insufficient amounts. Fiber-enhanced functional foods can increase fiber intake, and there is particular interest in resistant starch (RS) as a high-fiber ingredient. Studies show that high-amylose maize resistant starch, type 2 (HAM-RS2) improves acute and chronic glycemic responses, but more studies are needed in individuals at high risk of T2D with RS delivered in commonly consumed foods. Objective: The objective of this study was to examine the chronic effects of consuming bagels high in HAM-RS2 on fasting and postprandial glycemic markers in adults at increased risk of T2D. Methods: With the use of a randomized, double-blind crossover design, 24 men and women with a mean +/- SE age of 55.3 +/- 1.59 y and body mass index (in kg/m(2)) of 30.2 +/- 0.57 consumed 1 bagel containing 25 g HAM-RS2/d or 1 control wheat bagel/d for 56 d each, separated by a 4-wk washout. Fasting and postprandial oral-glucose-tolerance test (OGTT) glucose and insulin were measured on study days 1 and 57 of each bagel treatment. Results: The RS bagel treatment resulted in significantly lower fasting (22.1 %, P= 0.04), 2-h (23.3%, P < 0.008), and 3-h (18.9%, P= 0.05) insulin incremental areas under the curve and fasting insulin resistance (homeostasis model assessment of insulin resistance; 23.1 %, P = 0.04) than did the control bagel treatment. Fasting and postprandial OGTT glucose concentrations did not differ between the RS and control bagel treatments on study days 1 or 57. Conclusions: These data suggest that consumption of a high HAM-RS2 bagel improves glycemic efficiency by reducing the amount of insulin required to manage postprandial glucose while improving fasting insulin sensitivity in adults at increased risk of T2D. This research provides support for a feasible dietary strategy for T2D risk reduction. This trial was registered at clinicaltrials.gov as NCT02129946.