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Study Shows Glucose Consumption Increases Production of Destructive Free Radicals, Lowers Level of Key Antioxidant

Subjects consumed glucose equal to sugar content of two cola drinks

By Lois Baker

Release Date: August 16, 2000

BUFFALO, N.Y. -- Sugary foods, notoriously bad for your teeth, also may be bad for your blood vessels and many other areas of the body, University at Buffalo endocrinologists have found.

Their study, published in the August issue of The Journal of Clinical Endocrinology and Metabolism, shows that excess sugar in the bloodstream stimulates the generation of free radicals, the oxygen molecules known to damage cells lining blood vessels and many other organs.

In blood vessels, free-radical injury causes inflammation and initiates the accumulation of plaque that can lead to blocked arteries and cardiovascular disease.

"We've known for some time that eating certain foods, particularly those containing the antioxidant vitamins A, E and C, can help protect against damage from free radicals," said Paresh Dandona, M.D., UB professor of medicine, director of the Division of Endocrinology, Diabetes and Metabolism for UB and Kaleida Health, and senior author on the study. "This is the first time anyone has shown that nutrition has a role in generating free radicals."

Type II diabetes, a major research interest of Dandona and colleagues, is associated with an increase in free-radical generation, resulting in damage to fats, proteins and DNA. In earlier preliminary research, they had shown that when obese subjects lost weight, there was a commensurate drop in free radicals. This finding raised the possibility that certain types of food may be involved in producing free radicals.

To test his hypothesis, Dandona and colleagues selected glucose, the nutrient with the most direct impact on diabetics. They gave 14 healthy men and women who had fasted for 12 hours a drink composed of 75 grams of glucose -- the simplest form of sugar -- dissolved in 300 milliliters of water -- a little more than one cup. This amount of glucose is roughly equivalent to

the sugar content in two cans of a cola drink, Dandona said. Another six participants, who served as controls, drank a water-saccharin solution.

Researchers took blood samples from all participants before the glucose challenge and at one, two and three hours after.

Results showed there was no change in free-radical generation in samples taken from controls. However, in samples from subjects who drank the sugar water, free-radical generation increased significantly at one hour and more than doubled at two hours. The analysis also showed an increase in the key protein component of an enzyme that promotes free-radical generation.

At the same time, levels of a-tocopherol, the active form of vitamin E and a powerful antioxidant, fell about 4 percent by hour two and remained depressed at hour three.

"The link between nutrition and oxidative damage is important because oxidative damage of lipids -- low-density lipoproteins in particular -- may contribute to atherosclerosis," Dandona said. "Our work opens the way for an investigation of the effect of other macronutrients on free-radical generation and oxidative damage."

Also contributing to the study were Priya Mohanty, Wael Hamouda, Rajesh Garg and Husam Ghanim, all doctoral students working with Dandona, and Ahmed Aljada, Ph.D., UB research assistant professor of medicine.

The William G. McGowan Charitable Fund supported this research.