Glucose Appearance Rate Rather than the Blood Glucose Concentrations Explains Differences in Postprandial Insulin Responses between Wholemeal Rye and Refined Wheat Breads—Results from A Cross‐Over Meal Study

Scope Ingestion of rye bread leads to lower postprandial plasma insulin concentrations than wheat bread ingestion, but most often not too different glucose profiles. The mechanism behind this discrepancy is still largely unknown. This study investigates whether glucose kinetics may explain the observed discrepancy. Methods and results Nine healthy men participated in a crossover study, eating 50 g of available carbohydrates as either refined wheat (WB) or traditional wholemeal rye bread (WMR) during d‐[6,6‐2H2]glucose infusion. Labeled glucose enrichment is measured by an HPLC‐TOF‐MS method. The calculated rate of glucose appearance (RaE) is significantly lower after ingestion of WMR during the initial 15 min postprandial period. Additionally, the 0‒90 min RaE area under the curve (AUC) is significantly lower after ingestion of WMR, as is plasma gastric inhibitory polypeptide (GIP) at 60 and 90 min. Postprandial glycemic responses do not differ between the breads. Postprandial insulin is lower after ingestion of WMR at 45 and 60 min, as is the 0‒90 min AUC. Conclusion Ingestion of WMR elicits a lower rate of glucose appearance into the bloodstream compared with WB. This may explain the lower insulin response observed after rye bread ingestion, commonly known as the rye factor. Ingestion of rye bread leads to lower postprandial plasma insulin concentrations than wheat bread ingestion, but not to different glucose responses. Ingestion of wholemeal rye bread is shown to elicit a lower rate of glucose appearance in blood compared with refined wheat bread. This may explain the lower insulin response observed after rye bread ingestion, commonly known as the rye factor.