A small study carried out in the UK seems to support coffee's action on reducing diabetes risk.
Researchers from the University of Surrey report that not only caffeine but another compound in coffee, chlorogenic acid, alter the glycaemic response in the small number of individuals tested.
In a three-way, randomised, crossover study, nine healthy volunteers consumed either a control glucose solution, or 25g of glucose in a 400 ml caffeinated or decaffeinated coffee sample after fasting. Blood was tested frequently over the following three hours.
Glucose and insulin concentrations tended to be higher in the first 30 minutes after caffeinated coffee consumption than after consumption of decaffeinated coffee or in the control group, reported the researchers in this month's American Journal of Clinical Nutrition.
But both caffeinated and decaffeinated coffee significantly slowed secretion of glucose-dependent insulinotropic polypeptide compared with the control group.
Glucose and insulin profiles were consistent with the known metabolic effects of caffeine, said the researchers. But they also noted that gastrointestinal hormone profiles revealed delayed intestinal glucose absorption.
"Differences in plasma glucose, insulin, and gastrointestinal hormone profiles further confirm the potent biological action of caffeine and suggest that chlorogenic acid might have an antagonistic effect on glucose transport," concluded the researchers.
A study in the Lancet last year found that people could cut their risk of type 2 diabetes by half if they drank more than seven cups of coffee daily. But coffee drinking has also been found to raise homocysteine levels and risk factors for coronary heart disease. A European project is currently focusing on the conflicting effects of the beverage on human health.