Low‐dose acarbose does not delay digestion of starch but reduces its bioavailability

Abstract Aims Slowly digestible starch is associated with beneficial health effects. The glucose‐lowering drug acarbose has the potential to retard starch digestion since it inhibits α‐amylase and α‐glucosidases. We tested the hypothesis that a low dose of acarbose delays the rate of digestion of rapidly digestible starch without reducing its bioavailability and thereby increasing resistant starch flux into the colon. Methods In a crossover study, seven healthy males ingested corn pasta (50.3 g dry weight), naturally enriched with 13 C, with and without 12.5 mg acarbose. Plasma glucose and insulin concentrations, and 13 CO 2 and hydrogen excretion in breath were monitored for 6 h after ingestion of the test meals. Using a primed continuous infusion of D‐[6,6‐ 2 H 2 ] glucose, the rate of appearance of starch‐derived glucose was estimated, reflecting intestinal glucose absorption. Results Areas under the 2‐h postprandial curves of plasma glucose and insulin concentrations were significantly decreased by acarbose (−58.1 ± 8.2% and −72.7 ± 7.4%, respectively). Acarbose reduced the overall 6‐h appearance of exogenous glucose (bioavailability) by 22 ± 7% (mean ± se ) and the 6‐h cumulative 13 CO 2 excretion by 30 ± 6%. Conclusions These data show that in healthy volunteers a low dose of 12.5 mg acarbose decreases the appearance of starch‐derived glucose substantially. Reduced bioavailability seems to contribute to this decrease to a greater extent than delay of digestion. This implies that the treatment effect of acarbose could in part be ascribed to the metabolic effects of colonic starch fermentation.