Carbohydrate staple foods - facing the challenge to improve their quality for a better metabolic health

Carbohydrates are the main energy source in most European diets. Their metabolic effects depend on several aspects ranging from chemical structure to food matrix and food processing which are best captured by the combined consideration of dietary fiber, whole grain, glycemic index or load and dietary sugar.

In Northern and Central European diets, bread is a major carbohydrate source, however, beneficial metabolic effects of bread may be confined to breads rich in fiber, whole grain and/or with a low glycemic index (GI) only.

The five partners from Norway, Germany and Sweden in this consortium will run a 16-week RCT involving 250 persons at risk of type 2 diabetes (T2DM, as defined by intermediate HbA1c of 39-46 mmol/mol) to test a newly developed bread containing the oat-derived fiber beta-glucan characterized by a comparably low GI of 57 for its effects on glycemic control (i.e. HbA1c). A conventional high-fiber bread without oat-fiber beta-glucan and a high GI (>70) will serve as a comparator. Secondary outcomes include body weight and composition, serum lipids and hepatic steatosis index as well as, gastric emptying, satiety and postprandial glycaemia in response to morning and evening consumption in subgroups.

Furthermore, the long-term relevance of bread intake and carbohydrate quality (intake of dietary fiber and whole grain intake, dietary GI) for body weight and T2DM or glycemic control will be analyzed in observational cohorts involving healthy adults (HUSK study, Norway) followed up during middle age and in lean and obese children followed-up until adulthood (KFO and Life child, Germany). Alkyresorcinols, an accepted biomarker of wholegrain consumption will be measured in plasma samples of the cohorts using a rapid LC-MS based method and will supplement self-reported dietary data. Finally, RCTs and observational studies on the relevance of bread consumption for body weight, glycemic control/T2DM and associated cardiometabolic outcomes will be summarized in systematic reviews and meta-analyses.

Taken together this project will address the overall hypothesis that habitual consumption of a high-fiber bread option can form an integral part of a plant-based healthy diet associated with benefits for body weight and T2DM risk.