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MONDAY, Jan. 28 (HealthDay News) -- New research suggests the caffeine in those daily cups of java might spell blood sugar trouble for diabetics.
In a small group of 10 diabetics, glucose levels rose by 8 percent when participants took pills filled with the level of caffeine found in four cups of coffee.
"There's reason to believe that caffeine consumption -- and coffee is the most common source of caffeine -- may be harmful to people with type 2 diabetes and make it more difficult for them to keep their glucose levels under proper control," said study author James Lane, a professor of medical psychology at Duke University.
While some research has suggested that the antioxidants in coffee could prevent diabetes in women, laboratory tests have questioned whether caffeine disrupts the body's ability to process blood sugar. "We want to demonstrate that what we've seen in the lab takes place in the real world when people are living their normal lives," Lane said.
In the new study, researchers inserted a small sensor into the abdomens of 10 patients who had diabetes but didn't take insulin. The sensor kept track of blood sugar levels for up to 72 hours.
Over several days, the patients -- all coffee drinkers -- alternated between taking placebos and 500 milligrams of caffeine a day in capsule form. That level of caffeine is equal to four eight-ounce cups of coffee.
The findings appear in the February issue of Diabetes Care.
On days when they consumed the caffeine pills, the blood sugar levels of the patients went up by 8 percent compared to when they took placebos. Glucose also rose after meals, most notably after dinner when blood sugar levels grew by 26 percent.
There are a couple possible explanations, according to Lane. In one, caffeine may interfere with the transfer of glucose from blood into the cells of the body, boosting blood sugar levels. Another possibility, he said, is that caffeine may stimulate the liver to release glucose when it's not needed.
A researcher who studies coffee said the new study has some limitations. For one, it looks at effects over one day, rather than over the long term, said Rob van Dam, a research scientist at Harvard School of Public Health. For another, "it should be noted that effects of caffeine in capsules cannot be directly translated to effects of caffeinated coffee, as studies have previously found less pronounced effects of caffeinated coffee on blood glucose levels as compared with caffeine in isolation," he added.
What to do? Keep coffee consumption under control, Lane suggested. "It would be worthwhile for people with diabetes who drink coffee to try quitting for a time and see if their glucose improves," Lane said. "It's a simple thing that might make their diabetes better."
Decaf may also do the trick. Indeed, van Dam said a previous study showed decaffeinated coffee actually reduced spikes in glucose levels after people ate sugary food. "It may thus be useful for persons with diabetes to try switching from caffeinated to decaffeinated coffee and see whether this improves their glycemic control, he said.
More information
Learn more about diabetes from the National Institutes of Health.
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