UT Southwestern Researchers Recommend Very High Fiber Diet For Type II Diabetics

In the May 11 issue of The New England Journal of Medicine, Dr. Abhimanyu Garg, professor of internal medicine, and Dr. Manisha Chandalia, assistant professor of internal medicine, report that study patients who included 50 grams of fiber in their daily diet - about twice as much as the American Diabetes Association (ADA) recommends -- lowered their glucose levels by 10 percent. The average American consumes about 17grams of fiber a day.

The high-fiber diet also decreased insulin levels in the blood and lowered blood lipid concentrations in study patients with type II diabetes, or non-insulin dependent diabetes mellitus, the most prevalent type of diabetes.

Garg, principal author of the study and a senior investigator in the Center for Human Nutrition, said the study's results should encourage diabetics to pay more attention to the fiber content of the foods they eat.

"Diet is the mainstay of diabetes treatment but is often neglected," Garg said. "The study supports the view that diet can improve glucose and lipid levels and thus reduce the risk of long-term diabetic complications."

The diets were specially prepared and the fiber content of the high-fiber diet was achieved by incorporating foods naturally rich in fiber, particularly soluble fiber. Fiber supplements were not used. Foods provided to the patients included cantaloupe, grapefruit, oranges, papayas, raisins, beans, okra, sweet potatoes, winter and zucchini squash, granola, oat bran and oatmeal.

Thirteen patients, 12 men and one woman, were used in the study that took place at the National Institutes of Health-supported General Clinical Research Center at UT Southwestern.

Each patient ate the high-fiber diet and the moderate-fiber diet recommended by the ADA for six weeks, then switched to the other diet for six weeks. Both diets contained the same number and proportion of calories from carbohydrates, fats and proteins. Blood tests were made during the final week of each diet.

The ADA diet had 24 grams of fiber (8 grams of soluble fiber and 16 grams of insoluble fiber), while the high-fiber diet had 50 grams of fiber (25 grams each of soluble and insoluble fiber). Fiber is classified according to water solubility. Most foods, such as fruits, vegetables and grains, contain both types of fiber.

Three patients were treated with diet alone, and the other 10 were treated daily with 2.5 to 20 milligrams of glyburide - a medication used to treat diabetes - in addition to the diets. The glyburide dose remained constant throughout the study.

On the basis of previous studies conducted by Garg, the 2000 ADA diet supports diets rich in monounsaturated fats, such as those consumed in Mediterranean countries. The current study supports a less-emphasized aspect of the Mediterranean diet -- its content of fruits, vegetables and grains, which are rich sources of dietary fiber.

The study was funded by grants from the National Institutes of Health and the Ministry for Education, Research, Science and Technology in Germany.