Durham, N.C. — Is coffee good for you? There’s research on both sides, and a new Duke study weighed in on the effects of caffeine on diabetes.

Some people drink coffee for an energy boost. For people with the most common form of diabetes, caffeine in coffee or other beverages may create the wrong kind of boost – in blood sugar levels.

“So, it actually exaggerated the problems that were associated with diabetes,” said Duke Psychologist Dr. Jim Lane.

In a small Duke study, Lane teamed with endocrinologists and used a monitor to record three days of continuous blood sugar activity in people with Type 2 diabetes. They took measured doses of caffeine or a placebo with regular meals – equal to about four cups of coffee a day.

“On the day they had caffeine, their average daytime glucose was 8 percent higher, and their responses to each of the meals was significantly higher,” Lane said.

It's not clear why, but caffeine may affect insulin production in the same way that stress does. Stress increases two hormones – adrenaline and cortisol – that disrupt glucose metabolism. Healthy people may tolerate it, but not diabetics.

“It may make their symptoms, their disease worse and make their blood glucose harder for them to keep under control,” Lane said.

For Type 2 diabetics or people at risk of developing Type 2 diabetes, cutting out caffeine is worth a try.

Lane found that the extent to which blood glucose changes in the wrong direction is similar to the benefit of some oral medications many diabetics take.

The Duke study was published in the Journal of Diabetes Care.