MONDAY, July 26, 2004 (HealthDayNews) -- Consuming beverages that contain caffeine may not be a good idea if you have type 2 diabetes, researchers report.

In a small study, Duke University scientists found a link between caffeine at mealtime and increased glucose and insulin levels in people with type 2 diabetes. The finding suggests diabetics should reduce or eliminate caffeine in their diets, according to the report in the August issue of Diabetes Care.

"Caffeine seems to impair the metabolism of carbohydrates in patients who have type 2 diabetes," said lead author James D. Lane, an associate research professor of medical psychology at Duke University Medical Center. "So it seems to make diabetes worse."

Levels of glucose -- blood sugar -- are elevated in people with diabetes after a meal because the body isn't able to metabolize the glucose, Lane said.

"If your blood glucose goes higher after every meal, then your average blood glucose level is going to be higher, and that could aggravate diabetes or increase the risk of complications," he said.

Diabetes is a disease in which the body doesn't produce or properly use insulin, a hormone needed to convert glucose into energy for the body.

In their study, Lane and his team recruited 14 regular coffee drinkers who had had type 2 diabetes for at least a six months. These subjects took medications for their diabetes, but did not require insulin.

The researchers looked at how much caffeine the people consumed over a week. The subjects were also given two 125-milligram caffeine capsules or a dummy drug, which were taken with a commercial liquid meal (BoostR) that has 75 grams of carbohydrates.

Lane's team measured the patient's blood glucose levels before and after eating and taking the caffeine pills.

The researchers found caffeine did not affect glucose and insulin levels after fasting. However, the study participants who drank the liquid and then took a caffeine pill experienced a 21 percent increase in glucose and a 48 percent rise in insulin levels, compared to the other study subjects getting the placebo.

Lane's group also compared the effect of caffeine with the medications diabetics take to lower glucose after a meal. "We found that the size of the increase in glucose due to the caffeine is as large as the decrease that occurs when people take medications to lower glucose," he said.

Based on the findings of this small study, Lane believes that "people who have type 2 diabetes may be better off if they avoid caffeine."

Curiously, a study released earlier this year found that coffee can help to prevent the onset of type 2 diabetes, reducing the risk by almost 50 percent. However, the protective effects didn't become significant until people drank at least four cups a day.

Tomas de Paulis, a research assistant professor from the Vanderbilt Institute for Coffee Studies at Vanderbilt University, said, "It is well known that caffeine has a detrimental effect on glucose tolerance."

"What is less known is that coffee also contains compounds with the opposite effect. It is not coffee but the caffeine that should be avoided by diabetes patients," he added.

More information

The American Diabetes Association has plenty of information about the disease.

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