Rye-Based Evening Meals Favorably Affected Glucose Regulation and Appetite Variables at the Following Breakfast; A Randomized Controlled Study in Healthy Subjects

Abstract

Background: Whole grain has shown potential to prevent obesity, cardiovascular disease and type 2 diabetes. Possible mechanism could be related to colonic fermentation of specific indigestible carbohydrates, i.e. dietary fiber (DF). The aim of this study was to investigate effects on cardiometabolic risk factors and appetite regulation the next day when ingesting rye kernel bread rich in DF as an evening meal.

Method: Whole grain rye kernel test bread (RKB) or a white wheat flour based bread (reference product, WWB) was provided as late evening meals to healthy young adults in a randomized cross-over design. The test products RKB and WWB were provided in two priming settings: as a single evening meal or as three consecutive evening meals prior to the experimental days. Test variables were measured in the morning, 10.5-13.5 hours after ingestion of RKB or WWB. The postprandial phase was analyzed for measures of glucose metabolism, inflammatory markers, appetite regulating hormones and short chain fatty acids (SCFA) in blood, hydrogen excretion in breath and subjective appetite ratings.

Results: With the exception of serum CRP, no significant differences in test variables were observed depending on length of priming (P>0.05). The RKB evening meal increased plasma concentrations of PYY (0-120 min, P<0.001), GLP-1 (0-90 min, P<0.05) and fasting SCFA (acetate and butyrate, P<0.05, propionate, P = 0.05), compared to WWB. Moreover, RKB decreased blood glucose (0-120 min, P = 0.001), serum insulin response (0-120 min, P<0.05) and fasting FFA concentrations (P<0.05). Additionally, RKB improved subjective appetite ratings during the whole experimental period (P<0.05), and increased breath hydrogen excretion (P<0.001), indicating increased colonic fermentation activity.

Conclusion: The results indicate that RKB evening meal has an anti-diabetic potential and that the increased release of satiety hormones and improvements of appetite sensation could be beneficial in preventing obesity. These effects could possibly be mediated through colonic fermentation.

Trial registration: ClinicalTrials.gov NCT02093481.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1. Flow diagram of the study progress.

Fig 2. Incremental blood glucose—and serum insulin response after the standardized breakfast.

Mean incremental blood glucose (A) and serum insulin (B) changes (Δ) from fasting concentrations the next morning after one (1D) or three consecutive evening meals (3D) with RKB or WWB, respectively. Values are means ± SEM. Repeated measures; mixed model in SAS. RKB, rye kernel bread; WWB, white wheat bread.

Fig 3. p-GLP-1, p-PYY and p-ghrelin response after breakfast.

Mean concentrations of plasma GLP-1 (A), p-PYY (B) and p-ghrelin (C) post ingestion of one or three evening meals consisting of RKB or WWB. Values are means ± SEM. Repeated measures; mixed model in SAS. p, plasma; RKB, rye kernel bread; WWB, white wheat bread; 1D, single evening meal; 3D, three consecutive evening meals.

Fig 4. SCFA response at fasting and breath H2 response during the experimental day.

Fasting concentrations of total SCFA and acetate on the left y-axis, and of propionate and butyrate on the right y-axis (A) and mean postprandial breath H2 concentrations (B) at a standardized breakfast, following the evening meals with RKB or WWB ingested as a single evening meal (1D) or during three consecutive evenings (3D) prior to experimental day. Values are means ± SEM. Repeated measures; mixed model in SAS. p, plasma; RKB, rye kernel bread; SCFA, short-chain fatty acids; WWB, white wheat bread.

Fig 5. Postprandial responses of satiety, hunger and desire to eat during the experimental day.

Mean of subjective appetite ratings (VAS) of satiety (A), hunger (B) and desire to eat (C) during 3 h after breakfast following an evening meal of RKB or WWB with or without priming (1D and 3D respectively). Values are means ± SEM. Repeated measures; mixed model in SAS. RKB, rye kernel bread; WWB, white wheat bread; 1D, single evening meal; 3D, three consecutive evening meals; VAS, Visual Analogue Scale.