COFFEE IMPROVES GLUCOSE TOLERANCE

March 27, 2009 — Chlorogenic acid and trigonelline, which are present in coffee, may improve glucose tolerance, according to the results of a randomized cross-over trial reported online March 26 in Diabetes Care.

"In prospective cohort studies, higher coffee consumption has been associated with a lower risk of type 2 diabetes," write Aimιe E van Dijk, MSc, from the Institute for Health Sciences, VU University Amsterdam, in the Netherlands, and colleagues. "Associations have been similar for caffeinated and decaffeinated coffee suggesting that coffee components other than caffeine have beneficial effects on glucose homeostasis. Coffee is a major source of the phenolic compound chlorogenic acid and the vitamin B3 precursor trigonelline that have been shown to reduce blood glucose concentrations in animal studies."

The goal of this study was to determine the acute effects of decaffeinated coffee, chlorogenic acid, and trigonelline on glucose tolerance in 15 overweight men. During a 2-hour oral glucose tolerance test (OGTT), the investigators studied the effects on glucose and insulin concentrations of 12 g decaffeinated coffee, 1 g chlorogenic acid, 500 mg trigonelline, and placebo (1 g mannitol).

Coffee Components May Improve Glucose Tolerance

Compared with placebo, chlorogenic acid and trigonelline ingestion were associated with significant reductions in glucose (−0.7 ΅mol/L [P = .007] and −0.5 ΅mol/L [P = .024], respectively) and insulin (−73 pmol/L [P = .038] and −117 pmol/L [P = .007], respectively) concentrations 15 minutes after an OGTT. However, insulin and glucose area under the curve values during the OGTT were similar for each of the treatments vs placebo.

Limitations of this study include that multiple tests were conducted for different time points, increasing the likelihood of chance findings, and difficulty comparing the treatment effects because the decaffeinated coffee supplement contained substantially less chlorogenic acid and trigonelline than the doses given in isolation.

"Chlorogenic acid and trigonelline reduced early glucose and insulin responses during an OGTT," the study authors write. "This finding is consistent with the hypothesis that these compounds may contribute to the putative beneficial effect of coffee on development of type 2 diabetes."