Glucose Metabolism in Diabetics Further Impaired by Caffeine
DURHAM, N.C. -- Researchers at Duke University Medical Center have found a
strong correlation between caffeine intake at mealtime and increased glucose
and insulin levels among people with type-2 diabetes.
Although the participant pool was relatively small, the researchers believe
their findings are significant enough to suggest that diabetics who
regularly enjoy caffeinated beverages and are struggling to maintain their
glucose levels should consider reducing or eliminating caffeine in their
diets.
The researchers examined how oral caffeine capsules affected carbohydrate
metabolism in people with type-2 diabetes. In this population, decreases in
insulin sensitivity could result in exaggerated hyperglycemic responses to
glucose that would aggravate the glycemic dysregulation that is a hallmark
of this disease. Although they found that caffeine did not affect fasting
levels of blood glucose or insulin in comparison to placebo, they did find
significant effects on both following a meal. The meal, in this case, was
the commercial liquid meal supplement known as BoostR.
"In a healthy person, glucose is metabolized within an hour or so after
eating. Diabetics, however, do not metabolize glucose as efficiently," said
James D. Lane, Ph.D., associate research professor in the department of
psychiatry and behavioral sciences at Duke, and lead author of the study.
"It appears that diabetics who consume caffeine are likely having a harder
time regulating their insulin and glucose levels than those who don't take
caffeine."
His team's findings appear in the August 2004 issue of Diabetes Care.
The double-blind, placebo-controlled study enrolled 14 habitual coffee
drinkers who had at least a six-month history of type-2 diabetes but who did
not require insulin therapy as part of their treatment regimen.
Study participants were asked to complete a seven-day diary of caffeinated
beverage intake -- including the serving size and time of day for each drink
consumed. (Average caffeine consumption from all beverages was about 526
milligrams per day, based on the self-reported diary entries.) Participants
were then observed on two different mornings within a two-week period
following an overnight fast and abstinence from caffeine.
On the days they were observed, participants took their prescribed diabetes
medications according to their usual treatment regimen. After 30 minutes of
quiet rest, they provided a blood sample so researchers could record their
baseline fasting glucose level. Participants then consumed two 125-milligram
capsules of caffeine (or placebo) with water. After a 60-minute interval to
allow for caffeine absorption, a second fasting blood sample was taken.
Participants were then given an additional 125-milligram capsule (caffeine
or placebo) to take with a commercial liquid meal (BoostR) that contained 75
grams of carbohydrates. The third capsule was provided in order to maintain
caffeine levels in the blood. Additional blood samples were taken from
participants one and two hours after the meal, while they relaxed.
The researchers determined that caffeine had little effect on glucose and
insulin levels during fasting when compared to placebo. However, after
consuming the carbohydrates in the liquid meal, those who were given
caffeine experienced a 21 percent increase in their glucose level and a 48
percent increase in their insulin level.
"The goal of clinical treatment for diabetes is to keep the person's blood
glucose down," Lane said. "It seems that caffeine, by further impairing the
metabolism of meals, is something diabetics ought to consider avoiding. Some
people already watch their diet and exercise regularly. Avoiding caffeine
might be another way to better manage their disease. In fact, it's possible
that staying away from caffeine could provide bigger benefits altogether."
Lane and his team hope to begin enrolling participants in larger clinical
trials that use brewed coffee -- rather than oral caffeine capsules -- later
this year. Other authors of this study include Christina Barkauskas; Richard
Surwit, Ph.D.; and Mark Feinglos, M.D., all of Duke University Medical
Center.
posted by deverne @ 2:11 PM
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