title: Caffeine ingestion impairs insulin sensitivity in a dose-dependent manner in both men and women.
abstract: The effects of alkaloid caffeine on insulin sensitivity have been investigated primarily in men, and with a single caffeine dose most commonly of 5-6 mg·kg(-1) of body weight (BW). It is unknown if the effects of caffeine on glucose homeostasis are sex-specific and (or) dose-dependent. This study examined whether caffeine ingestion would disrupt glucose homeostasis in a dose-dependent or threshold manner. It also examined whether sex-specific responses to caffeine exist. It was hypothesized that women would have an exaggerated response to caffeine, and that caffeine would only impair glucose metabolism once a threshold was reached. Twenty-four healthy volunteers (12 males, 12 females) participated in 4 trials, in a crossover, randomized, and double-blind fashion. They ingested caffeine (1, 3, or 5 mg·kg(-1) of BW) or placebo followed, 1 h later, by a 2-h oral glucose tolerance test. Glucose, insulin, C-peptide area under the curve (AUC), and insulin sensitivity index data were fitted to a segmented linear model to determine dose-responses. There were no differences between sexes for any endpoints. Regression slopes were significantly different from zero (p < 0.05) for glucose, insulin, and C-peptide AUCs, with thresholds being no different from zero. Increasing caffeine consumption by 1 mg·kg(-1) of BW increased insulin and C-peptide AUCs by 5.8% and 8.7%, respectively. Despite this exaggerated insulin response, glucose AUC increased by 11.2 mmol per 120 min·L(-1) for each mg·kg(-1) BW consumed. These results showed that caffeine ingestion disrupted insulin sensitivity in a dose-dependent fashion beginning at very low doses (0-1 mg·kg(-1) BW) in both healthy men and women.
authors: a Department of Human Health and Nutritional Sciences, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada.
authors: Marie-Soleil
authors: MS
authors: Beaudoin
authors: Brian
authors: B
authors: Allen
authors: Gillian
authors: G
authors: Mazzetti
authors: Peter J
authors: PJ
authors: Sullivan
authors: Terry E
authors: TE
authors: Graham
mesh_terms: D000328:Adult; D001786:Blood Glucose; D002096:C-Peptide / Q000097:blood / Q000378:metabolism; D002110:Caffeine / Q000008:administration & dosage* / Q000494:pharmacology*; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D012737:Sex Factors; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D002096:C-Peptide; D007328:Insulin; D002110:Caffeine; D005947:Glucose