Dietary polyphenols may have biological effects in the small intestine that alter the pattern of glucose uptake. However, the effect on glucose tolerance in humans is unknown.
In this study, physicians from the England investigated whether the chlorogenic acids in coffee modulate glucose uptake, and gastrointestinal hormone and insulin secretion.
|Glucose and insulin concentrations were higher after caffeine consumption.|
|American Journal of Clinical Nutrition|
The team performed a 3-way, randomized, crossover study, in which 9 healthy fasted volunteers consumed 25g glucose, in either 400 mL water (control), or 400 mL caffeinated or decaffeinated coffee.
Blood samples were taken over the following 3 hours.
The researchers found that glucose and insulin concentrations were higher in the first 30 minutes after caffeinated coffee consumption versus decaffeinated coffee or the control.
They determined that glucose-dependent insulinotropic polypeptide secretion decreased throughout the experimental period. In addition, glucagon-like peptide 1 secretion increased 0 to 120 minutes postprandially after decaffeinated coffee consumption, compared with the control.
Glucose and insulin profiles were consistent with the known metabolic effects of caffeine.
However, the gastrointestinal hormone profiles were consistent with delayed intestinal glucose absorption.
Dr Kelly Johnston's team concluded, "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".
"Therefore, a novel function of some dietary phenols in humans may be to attenuate intestinal glucose absorption rates and shift the site of glucose absorption to more distal parts of the intestine".