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Diabetes Health Center

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Caffeine Risks May Rattle Diabetic People

Study Shows Caffeine Elevates Blood Glucose Levels in People With Diabetes
WebMD Health News
Reviewed by Louise Chang, MD

Jan 28, 2008 -- There's something about coffee that fights type 2 diabetes -- but it isn't caffeine.

Caffeine makes it hard for people with diabetes to control their blood sugar, new studies suggest.

In the latest of these studies, Duke University researcher James D. Lane, PhD, and colleagues put continuous blood-sugar monitors on 10 people with type 2 diabetes. All were regular coffee drinkers averaging four cups a day, but they stopped drinking coffee during the experiment.

On one day, each patient took a 250 mg caffeine capsule at breakfast and another 250 mg caffeine capsule at lunch. That's roughly the same as having them drink two cups of coffee at each meal. On another day, the same people got placebo pills with no caffeine in them.

The result: On the days the patients took caffeine, their blood-sugar levels were 8% higher. And after every meal -- including dinner -- their blood sugar spiked higher than it did on the day they had no caffeine.

"These are clinically significant blood-sugar elevations due to caffeine," Lane tells WebMD. "Caffeine increases blood glucose by as much as oral diabetes medications decrease it. ... It seems the detrimental effects of caffeine are as bad as the beneficial effects of oral diabetes drugs are good."

Lane warns against reading too much into this small, 10-patient study. But he says it does show that caffeine has real effects on the everyday lives of people with diabetes.

"For people with diabetes, drinking coffee or consuming caffeine in other beverages may make it harder for them to control their glucose," he says.

(If you have diabetes, how much caffeine do you consume on a regular basis? Talk with others on WebMD's Type 2 Diabetes Support Group message board.)

Diabetes, Coffee, and Caffeine

Several studies have found that coffee drinkers -- especially those who drink a lot of coffee -- have a lower risk of diabetes than do other people. So how can coffee both protect against diabetes and worsen diabetes?

WebMD took this question to Harvard researcher Rob van Dam, PhD, who recently analyzed all of these studies.

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