Postprandial Effects of Four Test Meals Containing Wholegrain Rye or Refined Wheat Foods on Circulating Incretins, Ghrelin, Glucose, and Inflammatory Markers.

Background: High intake of whole grains has consistently been associated with reduced risk of obesity, coronary heart disease, and type 2 diabetes. Dietary interventions have shown beneficial metabolic effects of whole grain, but the metabolic response varies with different types of cereals.

Objectives: We evaluate the metabolic effects of substituting refined wheat with wholegrain rye foods within a complex diet, examining day-long postprandial response of glucose-dependent insulinotropic peptide, (GIP), glucagon-like peptide-1 (GLP-1), ghrelin, glucose, and inflammatory biomarkers in overweight and obese individuals.

Methods: Twenty-nine healthy adults, BMI 32 ± 9 kg/m² were randomly assigned to three intervention days, separated by one-week washout. Participants adhered to a hypocaloric diet rich in wholegrain rye for one intervention and refined wheat for the second intervention and were randomized to either diet for the third intervention with continuous blood sampling.

Results: No differences in GIP, GLP-1 or ghrelin levels were found between the diets when measured throughout the whole intervention day. GIP tAUC following the rye-based lunch was 31% (p < 0.05) lower compared with the wheat-based lunch and ghrelin concentrations were 29% (p < 0.05) lower after the rye-based dinner. Baseline HOMA-IR adjusted model, showed 61% (p = 0.015) lower whole-day GLP-1 and 40% (p = 0.03) lower GIP following the rye-based diet. Day-long glucose iAUC was 30% (p <0.001) lower following the rye-based diet and glycemic variability measured as SD reduced (-0.13 mmol/L p = 0.04). The rye-based diet vs refined wheat induced higher glycoprotein N-acetylation A by z-scores (0.36, p = 0.014).

Conclusions: Overall, no day-long differences in gut hormone levels were observed, but the wholegrain rye-based vs refined wheat-based dinner showed lower postprandial ghrelin concentrations. The rye-based diet improved day-long glycemic control in individuals with overweight and obesity. Observations of diet-induced inflammation following whole-grain rye intake warrant further investigation. THIS STUDY WAS PROSPECTIVELY REGISTERED AT CLINICALTRIALS.GOV (NCT05004584): https://clinicaltrials.gov/study/NCT05004584?locStr=Gothenburg,%20Sweden&country=Sweden&state=V%C3%A4stra%20G%C3%B6taland%20County&city=Gothenburg&distance=50&term=appetite&aggFilters=status:com&rank=1.