Abstract and Introduction
Abstract
Objective—The epidemiological association between coffee drinking and decreased risk of type 2 diabetes is strong. However, caffeinated coffee acutely impairs glucose metabolism. We assessed acute effects of decaffeinated coffee on glucose and insulin levels.
Research design and methods—This was a randomized, cross-over, placebo-controlled trial of the effects of decaffeinated coffee, caffeinated coffee, and caffeine on glucose, insulin, and glucose-dependent insulinotropic polypeptide (GIP) levels during a 2-h oral glucose tolerance test (OGTT) in 11 young men.
Results—Within the first hour of the OGTT, glucose and insulin were higher for decaffeinated coffee than for placebo (P < 0.05). During the whole OGTT, decaffeinated coffee yielded higher insulin than placebo and lower glucose and a higher insulin sensitivity index than caffeine. Changes in GIP could not explain any beverage effects on glucose and insulin.
Conclusions—Some types of decaffeinated coffee may acutely impair glucose metabolism but less than caffeine.
Introduction
Nineteen of 22 epidemiological studies concluded that long-term consumption of coffee, both caffeinated and decaffeinated, can reduce the risk of type 2 diabetes, but several investigators have warned that the caffeine in caffeinated coffee can impair glucose metabolism (e.g., ). While decaffeinated coffee contains very little caffeine and may safely protect against diabetes, there have been conflicting reports on decaffeinated coffee's acute effects on glucose metabolism. Our objective was to assess whether ground decaffeinated coffee enhances glucose metabolism and whether glucose-dependent insulinotropic polypeptide (GIP), an incretin hormone that stimulates insulin secretion, plays a causal role.