Scientists are offering a new solution to the long-standing mystery of why heavy coffee drinkers have a lower risk of developing type 2 diabetes in a report in the American Chemical Society’s Journal of Agricultural & Food Chemistry.

Ling Zheng, Kun Huang and colleagues explain that previous studies show that coffee drinkers are at a lower risk for developing type 2 diabetes, which accounts for 90 to 95 percent of diabetes cases in the world. Those studies show that people who drink four or more cups of coffee daily have a 50 percent lower risk of type 2 diabetes. And every additional cup of coffee brings another decrease in risk of almost 7 percent.

Scientists have implicated the misfolding of a substance called human islet amyloid polypeptide (hIAPP) in causing type 2 diabetes, and some are seeking ways to block that process. Zheng and Huang decided to see if coffee’s beneficial effects might be due to substances that block hIAPP.

Indeed, they identified two categories of compounds in coffee that significantly inhibited hIAPP. They suggest that this effect explains why coffee drinkers show a lower risk for developing diabetes. “A beneficial effect may thus be expected for a regular coffee drinker,” the researchers conclude.