African-American and Chinese women who eat foods that are high on the glycemic index may carry a higher risk of developing type 2 diabetes, according to two recent university studies.

(The glycemic index ranks carbohydrates according to how fast the body converts them into glucose. Simple carbohydrates that are high on the index, such as white rice and potatoes, can cause blood sugar to rise rapidly. Carbohydrates ranking lower on the index, such as lentils and high-fiber grains, are more gradually absorbed and converted by the body.)

In the study of African-American women, Boston University School of Public Health began tracking the food consumption and health habits of 40,078 women in 1995. The study followed up with the women every two years thereafter, through 2003, with questions about their diet, health, and weight.

By 2003, 1,938 of the women had developed type 2 diabetes. Researchers concluded that women who had diets rich in high-glycemic index foods had a higher risk for diabetes. However, they also found that women who ate a diet high in cereal fiber considerably reduced their risk of acquiring type 2. For example, they said that consistently eating a cup of bran cereal with raisins (5 to 8 grams of fiber) or oatmeal (4 grams) at breakfast rather than a cup of Corn Chex (0.5 grams) or Rice Chex (0.3 grams) corresponded to a 10 percent reduction in risk.

High Rice Consumption Increases Risk

The other study, conducted by Vanderbilt University Medical Center, tracked 64,227 women in Shanghai, China, starting in 2000. Researchers interviewed the women every two years about their physical activity and diets. By the end of the study, 1,608 women had developed type 2 diabetes, which the study said coincided with carbohydrate intake.

Researchers had divided the women into five groups, based on their carbohydrate intake. Women in the group with the highest intake (337.6 grams per day) had a 28 percent higher risk of developing type 2 than women in the lowest intake group (263.5 grams per day). Women whose carbohydrate intake ended toward higher glycemic index foods such as bread, rice and noodles, also had an increased risk.

One of the most notable conclusions was that women who ate 300 grams or more of rice per day were 78 percent more likely to develop type 2 than women whose rice consumption was fewer than 200 grams per day.

Vanderbilt researcher Dr. Raquel Villegas, Ph.D., said that because a large part of the world's population consumes rice as a dietary mainstay, the linkage between the intake of refined carbohydrates and increased risk of type 2 has substantial implications for public health.