Eating that extra fry in the dining hall may be hazardous to your health.

According to a new study by the Harvard School of Public Health and Brigham and Women's Hospital, women who have diets low in fiber and high in refined sugar are two-and-a-half times more likely to develop the disease than their counterparts.

The long-term study related diet and lifestyle factors to chronic disease among more than 120,000 female registered nurses aged 30-55 years.

"Because these results are so strong and consistent with previous evidence about the productive benefits of a high fiber diet, we suggest that grains be consumed in a minimally refined form to reduce the risk of diabetes," said Dr. JoAnn E. Mason '75, an associate professor of medicine at Harvard Medical School (HMS), who was the principal investigator in the study.

Foods that the study recommends women should avoid include white bread, french fries, cola beverages and mashed potatoes--all of which have high amounts of refined sugar and cause a quicker rise in blood sugar levels than do high fiber foods, Mason said.

These foods, which are high in glycemic load, should be replaced with foods such as whole grain breads, high fiber breakfast cereals, beans and peanut butter.

According to Mason, the surge in blood sugar levels caused by foods high in glycemic load puts more strain on the pancreas, which increases the chances of both men's and women's contracting diabetes.

Adult-onset diabetes, also called Type II diabetes, has been found to increase the risk of heart disease and stroke by six times in women and by three to four times in men. It is the leading cause of new cases of blindness in adults and causes kidney failure and nerve damage.

The research was part of the Nurses' Health Study, directed by Dr. Frank E. Speizer, Kass professor of medicine at HMS.

The results, to be published in the Journal of the American Medical Association this week, will shed light on a disease that affects 14 million people in the U.S. alone