Previous studies have shown that higher coffee consumption was associated with a risk of type 2 diabetes. This association was similar for both caffeinated and decaffeinated coffee, suggesting that there was some component other than caffeine responsible for coffee's beneficial effects on blood sugar regulation. Now, researchers report that two coffee components, chlorogenic acid and trigonelline, may improve glucose tolerance, according to a study published online in Diabetes Care.

Impaired glucose tolerance is a pre-diabetic state that is associated with resistance to insulin and an increased risk of cardiovascular disease. The 2-hour oral glucose tolerance test (OGTT) is used to measure the body's ability to break down glucose, and it is commonly used to diagnose diabetes or pre-diabetes. Scientists from the Institute for Health Sciences, VU University Amsterdam in the Netherlands and their colleagues studied the effects of decaffeinated coffee, chlorogenic acid, trigonelline, and placebo on glucose and insulin concentrations during a 2-hour OGTT in fifteen overweight men. They found that chlorogenic acid and trigonelline ingestion significantly reduced glucose and insulin levels 15 minutes after an OGTT as compared with placebo.

Coffee is a major source of chlorogenic acid and trigonelline, and these compounds have been shown to reduce blood glucose concentrations in animal studies. This study shows that chlorogenic acid and trigonelline reduce early glucose and insulin responses, but further research in need to determine the long-term effects on glucose tolerance and the development of diabetes.