A Three-Day Intervention With Granola Containing Cereal Beta-Glucan Improves Glycemic Response and Changes the Gut Microbiota in Healthy Individuals: A Crossover Study

Abstract

Intake of soluble fibers including beta-glucan, is known to improve post-prandial glycemic response. The mechanisms have been attributed to the viscous gel forming in the stomach and small intestine, giving a longer absorption time. However, recent evidence suggests a link between intake of beta-glucan and improved glycemic regulation at subsequent meals through the gut microbiota. We investigated the short-term effect of granola with different amounts of cereal beta-glucan on glycemic response and gut microbiota. After a two-week run-in period (baseline), fourteen healthy, normal weight adults completed a dose-response dietary crossover study. Different amounts of cereal beta-glucan (low: 0.8 g, medium: 3.2 g and high: 6.6 g) were provided in granola and eaten with 200 ml low-fat milk as an evening meal for three consecutive days. Blood glucose and insulin were measured fasted and after an oral glucose tolerance test (OGTT) the following day, in addition to peptide YY (PYY) and glucagon-like peptide (GLP-2), fasting short chain fatty acids (SCFA) in blood, breath H2, and gut microbiota in feces. Only the intervention with medium amounts of beta-glucan decreased blood glucose and insulin during OGTT compared to baseline. Fasting PYY increased with both medium and high beta-glucan meal compared to the low beta-glucan meal. The microbiota and SCFAs changed after all three interventions compared to baseline, where acetate and butyrate increased, while propionate was unchanged. Highest positive effect size after intake of beta-glucan was found with Haemophilus, followed by Veillonella and Sutterella. Furthermore, we found several correlations between different bacterial taxa and markers of glycemic response. In summary, intake of granola containing 3.2 g cereal beta-glucan as an evening meal for three consecutive days reduced the glycemic response after an OGTT 0-180 min and changed gut microbiota composition. Since we cannot rule out that other fiber types have contributed to the effect, more studies are needed to further explore the effect of cereal beta-glucan on glycemic regulation.Clinical Trial Registration[www.clinicaltrials.gov], identifier [NCT03293693].

Therapeutic Potential of Fungal Polysaccharides in Gut Microbiota Regulation: Implications for Diabetes, Neurodegeneration, and Oncology

“…The HTCS consists of a single protein that extends across the cytoplasmic membrane and includes domains found in a typical two-component system: an extracellular sensor at the N-terminus, a cytoplasmic histidine kinase, and a response regulator [ 101 ]. The HTCS detects signals through the direct attachment of oligosaccharide fragments to the periplasmic sensor domain [ 102 ]. These oligosaccharides, results of polysaccharide breakdown by endo-acting enzymes encoded within the PUL anchored to the cell surface, are first moved into the periplasm by the SusC homolog, a TonB-dependent transporter.…”

The Effects of Soluble Dietary Fibers on Glycemic Response: An Overview and Futures Perspectives

“…When different amounts of cereal β-glucan (low: 0.8 g, medium: 3.2 g, and high: 6.6 g) were consumed in the evening meal for three days, only the medium intervention was able to reduce blood glucose and insulin during glucose tolerance (OGT) testing in the following day when compared to baseline. The authors considered the beneficial effects of β-glucan on glycemic regulation the following day are not dependent on viscosity [ 77 ]. However, some studies confirmed the dose–response hypothesis of β-glucan in relation to the glycemic response postprandial [ 67 , 73 ].…”

Effect of beta glucan coating on controlled release, bioaccessibility, and absorption of β-carotene from loaded liposomes

“…19 In particular, proven health benefits are glucose and cholesterol lowering effect, which reduce the risk of type II diabetes and cardiovascular disease [20][21][22] by reducing serum low-density lipoprotein (LDL)-cholesterol, improving glycaemic response and modulation of gut microbiota. 23,24 Cholesterol and plasma glucose lowering effect of βG is also associated with the increase in the viscosity of chyme, which affects gastrointestinal motility and hydrolysis rate in the GIT. 25 In addition to the higher viscosity effect in the upper GIT, βG may also alter the microviscosity of the mucus layer in the small intestine, hence decreasing its permeability by increasing overall polymer concentrations and decreasing porocity.…”

“…19 In particular, proven health benefits are glucose and cholesterol lowering effect, which reduce the risk of type II diabetes and cardiovascular disease 20–22 by reducing serum low-density lipoprotein (LDL)-cholesterol, improving glycaemic response and modulation of gut microbiota. 23,24 Cholesterol and plasma glucose lowering effect of βG is also associated with the increase in the viscosity of chyme, which affects gastrointestinal motility and hydrolysis rate in the GIT. 25…”