Scientists May Know Link Between Coffee and Diabetes

A group of Chinese researchers believe they may have found the mechanism by which coffee helps prevent type 2 diabetes. Scientists have been aware that coffee seems to reduce the risk of developing type 2 diabetes for some time now. The exact mechanism — even the substances in coffee that provide the protective effect — has been a mystery, however. Researchers Ling Zheng, of Wuhan University, and Kun Huang, of Huazhong University of Science and Technology, may have discovered the substances in coffee that are responsible for the lowered risk of type 2 diabetes in coffee drinkers.

Their study, published in the “Journal of Agricultural and Food Chemistry” focuses on a peptide found in the human pancreas — human islet amyloid polypeptide, usually abbreviated as hIAPP — which has been implicated in diabetes. The compound is found in higher concentration among those who have type 2 diabetes, and much of the recent research into prevention and treatment of diabetes has focused on ways to inhibit the misfolding of hIAPP.

Zheng and Huang noted that previous studies on coffee and diabetes risk show that people who drink four or more cups of coffee daily have a 50 percent lower risk of developing type 2 diabetes, and that each additional cup of coffee decreases the risk of developing diabetes by an additional 7 percent. They decided to examine the effect of several substances in coffee on hIAPP to determine if something in coffee might inhibit the misfolding of hIAPP.

They found that two of the compounds they tested do, indeed, have a significant inhibitory effect on the misfolding of hIAPP. Caffeic acid and cholorogenic acid both inhibit the development of toxic levels of hIAPP. Caffeine also has an inhibitory effect, but not to the same degree as caffeic acid and chlorogenic acid. The finding also may help explain a few of the specifics found in other studies regarding the link between coffee and diabetes.

Some researchers have found, for example, that those who drink decaffeinated coffee also benefit from a reduction in the risk of developing type 2 diabetes, but to a lesser extent than those who drink caffeinated coffee, while tea drinkers see no benefit at all. If caffeine is only one of the compounds in coffee that has an inhibitory effect on hIAPP, then it makes sense that decaf drinkers would see some benefit, but those who drink tea, which lacks the two significant acids, would see little or no benefit.

Likewise, some studies have noted a difference between those who drink filtered coffee and those who brew their coffee in a press pot or other unfiltered method. Filtered coffee generally has a lower level of the two acids than unfiltered coffee. Those who drink brews with robusta beans, typically added to espresso blends to give them an additional kick, may also see a greater benefit, because robusta also has a higher content of chlorogenic acid and caffeic acid.

The conclusion of the study calls for more research into the role of the two acids, and suggest research into synthesizing the compounds for use in anti-diabetes drugs. The study does require confirmation of the results in actual humans — the current research was carried out in vitro.

The researchers received funding for their research from the National Natural Science Foundation of China, the National Basic Research Program of China and the Chinese Ministry of Education.