The Effect of Particle Size of Whole-Grain Flour on Plasma Glucose, Insulin, Glucagon and Thyroid-Stimulating Hormone in Humans

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Abstract
Objective: Although it is well known that consumption of whole-grain foods with higher fiber content results in beneficial health effects, most Americans usually prefer bread made with white flour. Changes in bread texture and undesirable intestinal responses have been reported as reasons for avoiding consumption of whole-grain foods or high-fiber menus. The purpose of this study was to determine whether consumption of bread made with ultra-fine-ground whole-grain wheat flour retained beneficial effects while reducing undesirable effects. Methods: Twenty-six men and women, 31 to 55 years of age, consumed glucose solutions or bread made with traditional white, conventional whole-grain wheat (WWF), or ultra-fine whole-grain wheat (UFWF) flour (1 g carbohydrate/kg body weight) in a Latin square design after two days of controlled diet. The effect on glycemic response was determined by comparing blood variables, after a tolerance test with white bread, WWF bread, and UFWF bread, with those after a glucose tolerance test. Results: Men and women had similar responses to all tolerances except postprandial TSH. Glucose and insulin levels one half hour after the glucose load were significantly higher than after any of the bread tolerances. Glucose, but not insulin, areas under the curve were significantly higher after the glucose load than areas after the three breads. Consumption of UFWF resulted in glucose and insulin responses, as well as areas under the curve, similar to those after consumption of conventional whole-wheat bread. Conclusion: The particle size of whole grain wheat flour did not substantially affect glycemic responses.