On the list of foods for a diabetic to eat, foods that contain caffeine are generally prohibited. In general, caffeine raises blood sugars in people who have diabetes. This is because it can trigger the release of hormones that instruct the liver to release glucose. But recent research shows that all kinds of coffee are not necessarily harmful to diabetics. Black coffee raises blood sugars, but a light-roast decaffeinated coffee may actually help keep blood sugars down.
The effects of caffeine on blood sugars are not immediate. What caffeine does is to cause the pancreas to “dump” a large amount of insulin right after you drink the high-caffeine beverage. This actually lowers sugars if you happen to be eating a doughnut at the same time you are drinking coffee (not that diabetics should eat doughnuts). Unfortunately, after the pancreas releases the initial large amount of insulin, it goes back into a quiet mode. It does not continue to release insulin to clear sugar out of the bloodstream for two, three, four, or five hours after you eat. As more and more of your meal is digested, less and less of the released sugars are moved into the cells that need them. Blood sugars go up.
Decaffeinated light-roast coffee, however, does not have this effect. Without the stimulation of caffeine, the pancreas produces insulin as normally as it can. Light-roast coffees contain a chemical called trigonelline that dark-roast does not. This chemical not only does not interfere with blood sugars, it may protect against developing diabetes at all. So the rule for diabetics is:
- Coffee is OK,
- But light-roast, not black, and
Be sure to drink decaf.