Effects of indigestible carbohydrates in barley on glucose metabolism, appetite and voluntary food intake over 16 h in healthy adults

Abstract

Background: Recent knowledge in animals suggests that gut microbial metabolism may affect host metabolism, including appetite regulating hormones. The aim of the present study was to evaluate the potential effects of a whole grain barley kernel product, rich in intrinsic indigestible carbohydrates (dietary fibre and resistant starch), on markers of metabolism and appetite regulation in healthy subjects.

Methods: Boiled barley kernels (BK) or white wheat bread (WWB; reference) were provided as late evening meals to 19 young adults in random order using a cross-over design. During subsequent ad libitum standardized breakfast and lunch meals (10.5-16 h), blood was collected for analysis of glucose, plasma insulin, adiponectin, ghrelin, glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1), serum free fatty acids (FFA) and interleukin (IL)-6. In addition, appetite sensations, voluntary energy intake and breath H2 were determined.

Results: BK as evening meal increased plasma GLP-1 at fasting (P < 0.05) and during the experimental day (P < 0.01) compared with WWB. In addition the BK evening meal decreased fasting serum FFA (P < 0.05) and tended to decrease fasting serum IL-6 (P = 0.06). At lunch, preceded by BK evening meal, voluntary energy intake was decreased (P < 0.05) when compared to WWB evening meal. The BK evening meal decreased incremental blood glucose area (P < 0.01), promoted higher breath H2 (P < 0.001), maintained adiponectin concentrations (P < 0.05) and reduced perceived hunger (P < 0.05) during 10.5-16 h after the meal.

Conclusions: The results indicate that the BK evening meal, facilitate glucose regulation, increase the release of GLP-1, reduce subsequent energy intake while at the same time decreasing hunger over 2 subsequent meals, and reduce fasting FFA the subsequent morning, possibly mediated through gut microbial fermentation of the indigestible carbohydrates.

Figure 1

Breath H₂ excretion during the experimental day. Mean postprandial H₂ excretion 10.5-16 h post ingestion of evening meals with BK or WWB respectively. Values are means ± SEM. Dotted lines at the y-axes indicate weighted mean calculated for WWB (8.8 ppm) and BK (31 ppm), respectively. BK, barley kernel; H₂, breath hydrogen; WWB, white wheat bread.

Figure 2

Incremental blood glucose and plasma insulin response. Mean incremental blood glucose (A) and plasma insulin (B) changes (Δ) from fasting concentrations after evening meals with BK or WWB, respectively. Values are means ± SEM. BK, barley kernel; WWB, white wheat bread.

Figure 3

GLP-1 response. Mean concentration of plasma GLP-1 during the experimental day following evening meals with BK or WWB, respectively. Values are means ± SEM. BK, barley kernel; GLP-1, glucagone-like peptide-1; WWB, white wheat bread.

Figure 4

Ghrelin response after breakfast. Mean concentration of plasma ghrelin post ingestion of evening meals with BK or WWB, respectively. Values are means ± SEM. BK, barley kernel; WWB, white wheat bread.

Figure 5

Incremental adiponectin changes and IL-6 response. Mean incremental plasma adiponectin (A) changes (Δ) and mean concentration of serum IL-6 (B) during the experimental day following evening meals with BK or WWB, respectively. Values are means ± SEM. BK, barley kernel; IL-6, interleukin-6; WWB, white wheat bread.

Figure 6

Post-prandial responses of satiety, hunger and desire to eat. Mean subjective ratings of appetite (VAS) during 5.5 h after breakfast and lunch, following an evening meal of BK or WWB, respectively. Values are means ± SEM. BK, barley kernel; WWB, white wheat bread.