DURHAM, N.C., Jan. 28 (UPI) -- Caffeine in coffee, tea or soft drinks increases blood sugar levels for people with type 2 diabetes and may undermine disease control, a U.S. study found.

Scientists at Duke University Medical Center in Durham, N.C., measured participants' glucose -- sugar -- levels on a constant basis throughout the day.

Lead author Dr. James Lane, a psychologist, says the researchers tracked for the first time the impact of caffeine consumption as patients go about their normal, everyday lives.

Lane studied 10 patients with established type 2 diabetes who drank at least two cups of coffee every day and who were trying to manage their disease through diet, exercise and oral medications, but no extra insulin.

Each of the study subjects had a tiny glucose monitor embedded under their abdominal skin that continuously monitored their glucose levels over a 72-hour period, Lane said.

The study, published in the February issue of Diabetes Care, found that when the participants consumed caffeine, their average daily sugar levels went up 8 percent. In addition, caffeine also exaggerated the rise in glucose after meals: increasing by 9 percent after breakfast, 15 percent after lunch and 26 percent after dinner.