(Agencies)
Updated: 2008-01-29 09:23

WASHINGTON -- Cutting down on caffeine could help people with the most common form of diabetes better control their blood sugar levels, researchers said on Monday.

A waiter carries two cups of Turkish coffee at a coffee shop in Istanbul October 19, 2007. [Agencies]

Giving caffeine to a small group of people with type 2 diabetes caused their levels of the blood sugar glucose to rise through the day, especially after meals, researchers at Duke University Medical Center in Durham, North Carolina, found.

"Caffeine appears to disrupt glucose metabolism in a way that could be harmful to people with type-2 diabetes," James Lane, a Duke medical psychologist who led the study, said in a telephone interview.

Caffeine is found in coffee, tea and many soft drinks.

Diabetes is a condition in which one's blood glucose levels are too high. Having too much glucose in the blood can damage the eyes, kidneys and nerves, and diabetes can also lead to heart disease, stroke and limb amputations.

Type-2 diabetes is the form closely linked to obesity.

The new findings seem to run counter to previous research regarding diabetes and caffeine. Earlier studies indicated that people who drank coffee had a reduced risk of type-2 diabetes, and those who drank the most coffee had the lowest risk.

The researchers used new technology -- a tiny glucose monitor embedded under the abdominal skin -- to monitor the glucose levels continuously in 10 people, average age 63.

On days when the participants were given four tablets containing caffeine equivalent to four cups of coffee, their average daily sugar levels rose 8 percent compared to days when the same people were given four placebo tablets, the researchers reported in the journal Diabetes Care.

"What we are really showing here is that when people with type-2 diabetes who are regular coffee drinkers drink coffee, it produces an elevation in their glucose throughout the day above what it is if they don't have caffeine," Lane said.

"This suggests that people with diabetes might want to avoid coffee and other caffeinated beverages so that this exaggeration doesn't occur. They may find that it's easier for them to keep their glucose down if they avoid caffeine."

Lane cited two possible explanations.

Caffeine may interfere with the process that transports glucose from the blood into muscle and other cells in the body to be burned as fuel, he said. Caffeine also triggers the release of the hormone adrenaline, which can elevate blood sugar levels, he said.

A number of studies have provided various results about the health effects of caffeine.

For example, US researchers reported last Monday that pregnant women who drink two or more cups of coffee a day have twice the risk of a miscarriage as those who avoid caffeine. Other US researchers reported the next day that caffeine may lower a woman's chances of developing ovarian cancer.