Caffeine intake makes insulin
more resistant to changes in blood sugar levels, Canadian
researchers report. This effect was observed both in patients
with and those without diabetes and could not be reversed
with regular exercise or weight.
But before you throw away
your coffee mug -- these results may not apply to the popular
caffeinated beverage, the investigators note. In fact, previous
research has suggested that drinking coffee may cut the
risk of diabetes.
When sugar levels in the
blood get too high, insulin is released, which brings the
levels back down. With insulin resistance, also known as
decreased insulin sensitivity, sugar levels need to get
much higher before insulin release is triggered. Over time,
this resistance can cause problems and lead to diabetes.
"Through mechanisms that
have yet to be firmly established, caffeine attenuates any
of the beneficial effects of exercise or weight loss on
insulin resistance," Dr. Robert Ross of Queens University
in Kingston, Ontario, stated.
While the clinical implications
remain unclear, Ross added, the findings are a "red flag"
for doctors and are particularly important for obese patients
and those with diabetes.
Ross and his team evaluated
sugar metabolism in 23 men before and after a three-month
exercise program. Before and during the exercise program,
the men were given caffeine or inactive "placebo." The subjects
included eight sedentary lean men, seven obese men with
type 2 diabetes, and eight obese men without diabetes.
Before the exercise program,
caffeine reduced insulin sensitivity by 33 percent in the
lean and obese men and 37 percent in the men with diabetes
compared to placebo. After the exercise program, insulin
sensitivity fell 23 percent after caffeine intake in the
lean men, 26 percent in the obese men, and 36 percent in
the diabetic men.
Comparison of the two study
phases, showed that exercise did not improve insulin resistance
related to caffeine intake.
The findings, published in
the medical journal Diabetes Care, seem to contradict recent
reports that coffee intake may cut the risk of diabetes,
Ross noted. However, coffee contains several other substances
that may affect sugar metabolism, such as antioxidants,
potassium and magnesium. "When you give somebody caffeine
without all of the other substances that are in coffee you
have a very different situation," he added.
SOURCE: Diabetes Care, March