Caffeine decreases insulin sensitivity, possibly by increasing epinephrine release

Last Updated: 2002-02-08 9:08:16 EST (Reuters Health)

NEW YORK (Reuters Health) - Moderate amounts of caffeine decrease insulin sensitivity in healthy humans, according to a report in the February issue of Diabetes Care. This may be a result of increased levels of plasma epinephrine.

Dr. Paul Smits and colleagues from University Medical Center, Nijmegen, the Netherlands, conducted a randomized, double-blind, crossover study in 12 healthy subjects. After abstaining from caffeine intake for 72 hours, the subjects were given 3 mg/kg caffeine or placebo intravenously, and the researchers used hyperinsulemic-euglycemic glucose clamps to assess insulin sensitivity.

"Insulin sensitivity was calculated as whole-body glucose uptake corrected for the insulin concentration," the authors explain. "Caffeine decreased insulin sensitivity by 15% (p < 0.5 versus placebo)," they report.

"After caffeine administration, plasma free fatty acids increased (p < 0.05) and remained higher than during placebo," and there was a fivefold increase in plasma epinephrine (p < 0.0005), according to the report. Smaller increases were observed in plasma norepinephrine (p < 0.02) and blood pressure (p < 0.001).

Because methylxanthines interact with adenosine receptors, the investigators tested the effects of the adenosine reuptake inhibitor dipyridamole in an identical study with 10 subjects. They found that dipyridamole did not affect insulin sensitivity, so "peripheral adenosine receptor antagonism does not appear to contribute to this effect."

Habituation could alter these findings, Dr. Smits and colleagues point out. "Because tolerance may develop for the effects of caffeine, it is currently premature to advise against caffeine use in the management of insulin resistance," they say.

Diabetes Care 2002;25:364-369.

Copyright © 2002 Reuters Limited.