Caffeine ingestion before an oral glucose tolerance test impairs blood glucose management in men with type 2 diabetes.
Caffeine ingestion negatively affects insulin sensitivity during an oral glucose tolerance test (OGTT) in lean and obese men, but this has not been studied in individuals with type 2 diabetes. We examined the effects of caffeine ingestion on insulin and glucose homeostasis in obese men with type 2 diabetes. Men (n = 12) with type 2 diabetes (age = 49 +/- 2 y, BMI = 32 +/- 1 kg/m(2)) underwent 2 trials, 1 wk apart, in a randomized, double-blind design. Each trial was conducted after withdrawal from caffeine, alcohol, exercise, and oral hypoglycemic agents for 48 h and an overnight fast. Subjects randomly ingested caffeine (5 mg/kg body weight) or placebo capsules and 1 h later began a 3 h 75 g OGTT. Caffeine increased (P < 0.05) serum insulin, proinsulin, and C-peptide concentrations during the OGTT relative to placebo. Insulin area under the curve was 25% greater (P < 0.05) after caffeine than after placebo ingestion. Despite this, blood glucose concentration was also increased (P < 0.01) in the caffeine trial. After caffeine ingestion, blood glucose remained elevated (P < 0.01) at 3 h postglucose load (8.9 +/- 0.7 mmol/L) compared with baseline (6.7 +/- 0.4 mmol/L). The insulin sensitivity index was lower (14%, P = 0.02) after caffeine than after placebo ingestion. Overall, despite elevated and prolonged proinsulin, C-peptide, and insulin responses after caffeine ingestion, blood glucose was also increased, suggesting an acute caffeine-induced impairment in blood glucose management in men with type 2 diabetes.
Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, ON, Canada. Lrobinso@uoguelph.ca
Lindsay E
LE
Robinson
Sonali
S
Savani
Danielle S
DS
Battram
Drew H
DH
McLaren
Premila
P
Sathasivam
Terry E
TE
Graham
D000328:Adult; D019540:Area Under Curve; D001786:Blood Glucose / Q000187:drug effects*; D002110:Caffeine / Q000494:pharmacology*; D003920:Diabetes Mellitus / Q000097:blood*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D004311:Double-Blind Method; D005947:Glucose / Q000378:metabolism*; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008297:Male; D008875:Middle Aged; D009765:Obesity; D011384:Proinsulin / Q000097:blood / Q000187:drug effects
D001786:Blood Glucose; D007328:Insulin; D002110:Caffeine; D011384:Proinsulin; D005947:Glucose