Beneficial glycaemic effects of barley bread compared to wheat bread in type 2 diabetes

Abstract

Abstract Background: Cereals foods with a high content of dietary fibres or amylose have potential to lower postprandial glucose levels. Optimisation of cereal foods may delay development of or improve management of type 2 diabetes (T2D). Methods: We investigated the impact on postprandial glucose metabolism of bread made of hulless barley flour (50% or 75%) and wheat flour (50% or 25%) or an RNAi-based amylose-only barley flour (AmOn) (50%) and wheat flour (50%) in subjects with T2D. Design: Twenty adults with T2D were randomly allocated to one of four bread each corresponding to 50 g carbohydrate at four separate visits. We measured fasting and 4h postprandial responses of glucose, insulin, glucagon, triacylglycerol, free fatty acids, glucagon-like peptide-1 and gastric inhibitory polypeptide. Mixed model ANOVA was used to examine the differences. Results: Bread made from 50% AmOn lowered the postprandial glucose by 34%, 27%, 23% (P < 0.05) compared with 100% wheat, 50% or 75% hulless barley, respectively. Bread made from 75% hulless barley reduced the postprandial glucose by 11% (P < 0.05) compared to 100% wheat bread. Postprandial insulin responses were reduced for 50% AmOn by 24% and 35% (P < 0.05) compared with 100% wheat and 50% hulless barley, respectively. Postprandial insulin was reduced by 22% (P < 0.05) for 75% compared to 50% hulless barley bread. Conclusions: Bread made by replacing wheat flour with either 75% hulless barley or 50% AmOn flour lowered postprandial glucose responses compared to 100% wheat bread indicating a beneficial impact in management of T2D. This trial was registered at clinicaltrials.gov as NCT04646746.