James D. Lane, PhD Responds:

James D. Lane, PhD, a professor of medical psychology and behavioral medicine at Duke University medical center, in Durham, North Carolina, responds: Caffeine has widespread effects in the body, including those on insulin and glucose metabolism, which could adversely influence your health. Research shows that caffeine diminishes the body's sensitivity to the actions of insulin, making the hormone less useful at moving glucose into cells, where it is burned as fuel. As a result, the pancreas must release more insulin to break down carbohydrates. Evidence suggests that this response doesn't disappear as long as caffeinated beverages are consumed daily. Decreased insulin sensitivity and the resulting high insulin levels after meals may contribute to the risk of developing diabetes. In those who already have type 2 diabetes, caffeine can exaggerate the abnormal rise in glucose after meals that can aggravate attempts to keep blood glucose under control.

It's not yet known whether abstaining from caffeine will improve glucose control and help prevent diabetes, but some evidence suggests that eliminating caffeine from the diet might be worth trying if insulin and glucose levels are a concern. But check with your doctor to learn what's right for you.