Effects of a brown beans evening meal on metabolic risk markers and appetite regulating hormones at a subsequent standardized breakfast: a randomized cross-over study

Abstract

Background: Dietary prevention strategies are increasingly recognized as essential to combat the current epidemic of obesity and related metabolic disorders. The purpose of the present study was to evaluate the potential prebiotic effects of indigestible carbohydrates in Swedish brown beans (Phaseolus vulgaris var. nanus) in relation to cardiometabolic risk markers and appetite regulating hormones.

Methods: Brown beans, or white wheat bread (WWB, reference product) were provided as evening meals to 16 healthy young adults in a randomised crossover design. Glucose, insulin, appetite regulatory hormones, GLP-1, GLP-2, appetite sensations, and markers of inflammation were measured at a following standardised breakfast, that is at 11 to 14 h post the evening meals. Additionally, colonic fermentation activity was estimated from measurement of plasma short chain fatty acids (SCFA, including also branched chain fatty acids) and breath hydrogen (H2) excretion.

Results: An evening meal of brown beans, in comparison with WWB, lowered blood glucose (-15%, p<0.01)- and insulin (-16%, p<0.05) responses, increased satiety hormones (PYY 51%, p<0.001), suppressed hunger hormones (ghrelin -14%, p<0.05), and hunger sensations (-15%, p = 0.05), increased GLP-2 concentrations (8.4%, p<0.05) and suppressed inflammatory markers (IL-6 -35%, and IL-18 -8.3%, p<0.05) at a subsequent standardised breakfast. Breath H2 (141%, p<0.01), propionate (16%, p<0.05), and isobutyrate (18%, P<0.001) were significantly increased after brown beans compared to after WWB, indicating a higher colonic fermentative activity after brown beans.

Conclusions: An evening meal with brown beans beneficially affected important measures of cardiometabolic risk and appetite regulatory hormones, within a time frame of 11-14 h, in comparison to a WWB evening meal. Concentrations of plasma SCFA and H2 were increased, indicating involvement of colonic fermentation. Indigestible colonic substrates from brown beans may provide a preventive tool in relation to obesity and the metabolic syndrome.

Trial registration: ClinicalTrials.gov NCT01706042.

Figure 1. CONSORT flowchart, flow diagram of the study progress.

Figure 2. Mean incremental changes (Δ) in blood glucose concentrations after the standardized breakfast consumed 11 hours after evening meals composed of brown beans or WWB.

A significant treatment (type of evening meal) effect was found over the test period (p<0.05, PROC MIXED in SAS release 9.2; SAS Institute Inc, Cary, NC). n = 16 subjects.

Figure 3. Mean incremental changes (Δ) in serum insulin concentrations after the standardized breakfast consumed 11 hours after evening meals composed of brown beans or WWB.

A significant treatment (type of evening meal) effect was found over the test period (p<0.05, PROC MIXED in SAS release 9.2; SAS Institute Inc, Cary, NC). n = 16 subjects.

Figure 4. Concentrations of serum IL-6 fasting and after a standardized breakfast, consumed 11 hours after evening meals composed of brown beans or WWB.

A significant treatment effect (type of evening meal) was found over the test period (p<0.05, PROC MIXED in SAS release 9.2; SAS Institute Inc, Cary, NC). n = 16 subjects.

Figure 5. Concentrations of serum IL-18 fasting and after a standardized breakfast, consumed 11 hours after evening meals composed of brown beans or WWB.

A significant treatment effect (type of evening meal) and treatment*time interaction were found over the test period (p<0.05 and p<0.001, respectively, PROC MIXED in SAS release 9.2; SAS Institute Inc, Cary, NC). n = 16 subjects.

Figure 6. Concentrations of plasma PYY fasting and after a standardized breakfast, consumed 11 hours after evening meals composed of brown beans or WWB.

A significant treatment effect (type of evening meal) was found over the test period (p<0.0001, PROC MIXED in SAS release 9.2; SAS Institute Inc, Cary, NC). n = 16 subjects.

Figure 7. Concentrations of plasma oxyntomodulin fasting and after a standardized breakfast, consumed 11 hours after evening meals composed of brown beans or WWB.

A significant treatment effect (type of evening meal) was found over the test period (p<0.05, PROC MIXED in SAS release 9.2; SAS Institute Inc, Cary, NC). n = 16 subjects.

Figure 8. Concentrations of plasma ghrelin fasting and after a standardized breakfast, consumed 11 hours after evening meals composed of brown beans or WWB.

A significant treatment effect (type of evening meal) was found over the test period (p<0.05, PROC MIXED in SAS release 9.2; SAS Institute Inc, Cary, NC). n = 16 subjects.

Figure 9. Concentrations of plasma GLP-2 fasting and after a standardized breakfast, consumed 11 hours after evening meals composed of brown beans or WWB.

A tendency was found towards a meal*time interaction in the postprandial period after the standardized breakfast (p = 0.065, PROC MIXED in SAS release 9.2; SAS Institute Inc, Cary, NC), revealing a higher plasma GLP-2 in the later postprandial period when the subjects consumed brown beans as an evening meal compared with the WWB (60–180 min, p<0.05). n = 16 subjects.