Acute effects of light and dark roasted coffee on glucose tolerance: a randomized, controlled crossover trial in healthy volunteers

Purpose Epidemiological evidence suggests that coffee consumption is associated with a lower risk of type 2 diabetes. Coffee contains caffeine and several other components that may modulate glucose regulation. The chlorogenic acids (CGA) in coffee have been indicated as constituents that may help to normalize the acute glucose response after a carbohydrate challenge. The aim of this study was to investigate whether two coffee beverages that differ in CGA content due to different roasting degrees will differentially affect glucose regulation. Methods In a controlled crossover trial, 11 healthy fasted volunteers consumed 300 mL of either light (LIR) or dark (DAR) roasted coffee, or water, followed 30 min later by a 75-g oral glucose tolerance test (OGTT). Blood samples were drawn at baseline, 30, 60, and 120 min. Differences in glucose and insulin responses and insulin sensitivity index (ISI) were analyzed. The CGA and caffeine contents in the coffees were analyzed using UPLC-MS/MS. Results No differences in glucose area under the curve (AUC) were found between treatments. Glucose concentrations were higher at 60 min after ingestion of DAR compared with water, while ingestion of LIR showed similar glucose concentrations as ingestion of water. Insulin AUC was higher after ingestion of DAR compared with water, and both coffees raised insulin concentrations and reduced ISI compared with water, with no difference between the two coffees. Conclusion Two coffees with different CGA contents did not differentially affect glucose or insulin responses during an OGTT, but both increased the insulin response compared with water.