Ingestion of caffeinated coffee impairs blood glucose homeostasis in response to either high or low glycemic index cereals in non-obese males

To examine the effects of caffeine fasted subjects ingested either caffeinated (COFFEE; ∼5mg/kg bw) or decaffeinated coffee (DECAF) and 1 h later consumed carbohydrates (75 g) as either a high or low glycemic index (GI) meal (GI: 81 & 41, respectively). Ten males withdrew from caffeine, alcohol and exercise for 48h and underwent 4 randomized trials. Insulin and blood glucose were not affected by COFFEE or DECAF prior to cereal ingestion. During the postprandial period, COFFEE resulted in a 29 and 44% greater (p < 0.05) area under the curve (AUC) for insulin in the high and low GI trials, respectively. COFFEE resulted in elevated blood glucose (p < 0.05). Following high GI meal, glucose AUC was 253.4 ± 39.5 & 102.6 ± 39.2 mM/L/2h for COFFEE and DECAF, respectively, whereas, after the low GI meal glucose AUC was 130.5 ± 23.3 & 41.3 ± 17.8 mM/L/2h for COFFEE and DECAF, respectively. Thus, caffeinated coffee combined with carbohydrates induced an acute insulin resistant state.