NEW YORK (Reuters Health) - Preliminary findings from a small study suggest that drinking moderate amounts of coffee may put healthy individuals at risk for decreased insulin sensitivity, or an inability to process blood sugar efficiently. Decreased insulin sensitivity is a precursor to diabetes.

"Our finding may have serious health implications, especially when superimposed on already-disturbed glucose tolerance or established (type 2) diabetes," write lead study author Dr. Gerben B. Keijzers and colleagues from University Medical Center in Nijmegen, the Netherlands.

But because more study is needed, "it is currently premature to advise against caffeine use," the researchers add.

Keijzers and colleagues studied 12 healthy individuals who, after abstaining from caffeine for 72 hours, were intravenously given moderate doses of either caffeine or an inactive substance.

Caffeine reduced insulin sensitivity by 15% among the study group, the researchers report in the February issue of Diabetes Care. The decrease in insulin sensitivity was comparable to the increase in sensitivity produced by taking diabetes drugs.

The caffeine group also had higher blood levels of free fatty acids than their peers in the comparison group, the report indicates.

Caffeine's ability to decrease insulin sensitivity could occur because the drug boosts levels of free fatty acids, as well as the hormone epinephrine, the authors suggest. The caffeine group exhibited a five-fold increase in blood levels of the hormone, the report indicates.

In an accompanying editorial, Drs. Italo Biaggioni and Stephen N. Davis of Vanderbilt University in Nashville write that Keijzers' study "adds another item to the list of potential deleterious effects of caffeine."

But coffee drinkers should not panic, Biaggioni told Reuters Health.

"The study was performed under artificial experimental conditions in normal people," he said. "The conclusions, therefore, are not immediately applicable to the rest of us, to obese people or to patients with diabetes."

"Coffee is, in general, a safe substance," Biaggioni said. "However, every substance, even aspirin, may be dangerous to some people, or if we take too much of it."

"Talk to your doctor if you think you are drinking too much coffee or if your diabetes is not well controlled," he advised.

SOURCE: Diabetes Care 2002;25:364-369.

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