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[IP] Caffeine Decreases Insulin Sensitivity

Caffeine Decreases Insulin Sensitivity, Possibly by
Increasing Epinephrine Release

NEW YORK (Reuters Health) Feb 08 - 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 <

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. 

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