A double-blind randomised controlled trial testing the effect of a barley product containing varying amounts and types of fibre on the postprandial glucose response of healthy volunteers

The aim of the present study was to determine if the consumption of barley tortillas varying in fibre and/or starch composition affected postprandial glucose, insulin, glucagon-like peptide-1 (GLP-1) or peptide YY concentrations. A double-blind, randomised, controlled trial was performed with twelve healthy adults. They each consumed one of five barley tortillas or a glucose drink on six individual visits separated by at least 1 week. Tortillas were made from 100% barley flour blends using five different milling fractions to achieve the desired compositions. All treatments provided 50g of available carbohydrate and were designed to make the following comparisons: (1) low-starch amylose (0%) v. high-starch amylose (42%) with similar β-glucan and insoluble fibre content; (2) low β-glucan (4.5g) v. medium β-glucan (7.8g) v. high β-glucan (11.6g) with similar starch amylose and insoluble fibre content; and (3) low insoluble fibre (7.4g) v. high insoluble fibre (19.6g) with similar starch amylose and β-glucan content. Blood was collected at fasting and at multiple intervals until 180 min after the first bite/sip of the test product. Amylose and insoluble fibre content did not alter postprandial glucose and insulin, but high-β-glucan tortillas elicited a lower glucose and insulin response as compared to the low-β-glucan tortillas. The tortillas with high insoluble fibre had a higher AUC for GLP-1 as compared to the tortillas with low insoluble fibre, whereas amylose and β-glucan content had no effect. Results show that processing methods can be used to optimise barley foods to reduce postprandial blood glucose responses and factors that may influence satiety.