Researchers in the US say that although there are no gudielines warning patients with diabtetes against consuming caffeine, that may have to change.
The study, conducted by Dr.James Lane from Duke Univesity Medical Center, in Durham, North Caroina, is the first to track the impact of caffeine consumption as patients go about their normal lives.
Researchers monitored 10 regular coffee drinkers with established type 2 diabetes who were managing their disease through diet and exercise but with no extra insulin.
The patients were fitted with a tiny monitor which continously tracked their glucose levels over a 72-hour period. Each took capsules equal to four cups of coffee on one day, and identical capsules containing a placecbo on another.
All were free to eat whatevevr they liked. Researchers found that when the participants cconsumed caffeine, their average daily sugar levels went up eight percent.
Caffeine also exaggerated the rise in glucose after meals, increasing by nine percent after breakfast, 15 percent after lunch and 26 percent after dinner.
The findings, which appear in the February issue of Diabetes care, add more weight to a growing body of research which suggests eliminating caffeine from the diet might be a good way to manage blood sugar levels.
Dr.Lane said: "Coffee is such a common drink in our society that we forget that it contains a very powerful drug - Caffeine. Our study suggests that one way to lower blood sugar is to simply quit drinking coffee, or any other caffeinated beverages."
It futher studies corrborate the results, Dr.Lane says there would be a case for doctors to instruct patients with diabetes to banish caffeine from their diets altogether.