Caffeine Impairs Sugar Metabolism

Caffeine intake has a negative effect on insulin sensitivity in men with and without type 2 diabetes, and this effect persists even with regular exercise and loss of adiposity. 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.

Dr. Robert Ross of Queens University in Kingston, Ontario, stated that, "Through mechanisms that have yet to be firmly established, caffeine attenuates any of the beneficial effects of exercise or weight loss on insulin resistance."

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, 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. "What is clear," he continued, "is that caffeine has a very powerful physiological effect."
Diabetes Care 2005;28:576-572.

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DID YOU KNOW:
An estimated 41 million adults ages 40 to 74 have pre-diabetes, according to the NIH. The National Diabetes Education Program (NDEP) has recently launched a public awareness campaign to address this patient population. The campaign, called “It’s Not Too Late to Prevent Diabetes. Take Your First Step Today,” is tailored to older individuals and informs them about ways to prevent or delay type 2 diabetes. The targeted measures of the NDEP include radio and print public service advertisements, tip sheets, and posters. Campaign materials are available on the NDEP website at www.ndep.nih.gov/diabetes/pubs/nottoolate_tips.pdf