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Research: Caffeine May Impair Metabolism

This might not be unexpected, but the following article discusses the effect that caffeine appears to have on insulin levels. Whether or not this applies to all people or only certain groups of people isn’t clear.

What I believe is clear, is that if you drink a lot of caffeine and you are prone to insulin insensitivity you might be making it harder for your body to mobilize fat stores. Anyway, here’s the item…

[i]A wake-up call for coffee drinkers: Research suggests caffeine consumption could impair metabolism
October 22, 2004
Heather Scott

The welcome buzz from a morning cup of coffee can increase alertness and reaction time. But research at the University of Guelph shows it also impairs the body’s ability to manage glucose in the long term. This could spell danger for pregnant women, Type 2 diabetics and obese or sedentary individuals.

Profs. Terry Graham and Lindsay Robinson, Department of Human Biology and Nutritional Sciences and former graduate students Lesley Moisely and Sita Kacker have been studying the “real-life” effects of caffeine on the metabolism. Their findings suggest that caffeine actually slows metabolism, something that may take coffee drinkers by surprise.

“We have the naive impression that nutrition is simple ? there are fats, there are carbohydrates and the rules are the same for everyone,” says Graham. “But this study has shown that the reality is very different.”

Graham’s team studied the effects of caffeine following in a typical breakfast of coffee and cereal. For the study, 10 healthy male participants aged 20 to 27 were given either caffeinated coffee, decaffeinated coffee or water, along with a serving of cereal and milk. Following breakfast, all of the participant?s blood glucose (sugar) levels rose as they digested the meal. Their bodies naturally responded to the excess glucose by releasing insulin, to prevent glucose levels from rising too high, says Graham, which is a normal response.

But the caffeinated coffee drinkers released much more insulin than other participants. In theory, the large amount of insulin released in the body should have caused the glucose levels to drop quickly. But, three hours later, the glucose levels of the coffee drinkers had still not returned to normal. This suggests that caffeine reduces insulin’s effectiveness - a condition known as insulin resistance.
Participants consumed a second meal three hours after breakfast, but this time without coffee. The insulin and glucose levels of the coffee drinkers spiked after the second meal, surpassing the levels of the decaf and water drinkers. Their glucose levels were still far above average five hours after the morning coffee, suggesting that the caffeine continued to cause insulin resistance long after it was consumed.

Graham says the body can take up to 24 hours to eliminate caffeine, which means an 11 a.m. coffee break could affect the body?s ability to digest an evening snack. This doesn?t pose a significant problem for most people, but complications could emerge for people who are already struggling to manage glucose, such as type 2 diabetics and gestational diabetics (women who contract diabetes during their pregnancy). Presently, Robinson and the research team have a paper in press in The Journal of Nutrition, showing that type 2 diabetics are more insulin-resistant when caffeine ingestion precedes carbohydrate consumption.

Diabetics don’t have extra insulin reserves. When diabetic people use caffeine, their bodies can?t increase insulin production to manage glucose levels. This can cause blood glucose levels to soar dangerously high, suggesting that diabetics or those at-risk for diabetes might be better off to limit caffeine, Graham says.
This research is sponsored by the Natural Sciences and Engineering Research Council.[/i]