Gender and body mass index modify the effect of increasing amounts of caffeinated coffee on postprandial glucose and insulin concentrations; a randomized, controlled, clinical trial

Objective. To examine the effects of different coffee amounts on blood glucose and insulin concentrations of healthy volunteers, and to assess potential effect modification by sex and body mass index category. Materials/Methods. Thirty-three volunteers [16 female/17 male, 16 normal-weight and 17 overweight/obese, 27.3 +/- 7.2 (19-44) y] took part in this randomized, crossover study. In the morning of each experimental day volunteers received a standardized meal along with 200 mL of water or instant coffee containing either 3 or 6 mg of caffeine/kg body weight. Blood samples were obtained and analyzed for glucose and insulin concentrations in the fasting state, immediately after meal/drink consumption and at standard time points for the next 3 h thereafter. Results. Coffee delayed the rise of insulin in response to the standardized meal and the fall of glucose concentrations from its maximum levels in the entire study sample. Glucose incremental area under the curve (IAUC) was significantly different between interventions (P = .009) with both coffee amounts inducing a greater area compared to water. Secondary, subgroup analysis at the nominal level showed that this might be more evident among females (P-IAUC = .05) and overweight/obese participants (P-IAUC = .03). Furthermore, coffee, mainly the 6 mg dose, could be lowering insulin concentrations the first 30 min after its consumption compared to water in men and overweight/obese participants. Conclusions. Coffee exerts an acute effect on postprandial glucose and insulin concentrations. This effect may be modified by sex and overweight/obese status. Future research is necessary to elucidate underlying mechanisms. (C) 2013 Elsevier Inc. All rights reserved.