WASHINGTON (Reuters, Nov 27) - Starchy foods such as white rice and bread raise the likelihood of diabetes for both black and Chinese women, but adding some whole-grain foods may reverse the risk, researchers reported on Monday.

Two studies -- the first to look at this aspect of diabetes risk in non-white women -- both show that eating refined carbohydrates can boost rates of diabetes.

One of the studies published in the Archives of Internal Medicine showed that women who ate the most fiber had the lowest risk of diabetes.

And both support the theory of glycemic index, which holds that certain types of carbohydrates such as sugars and refined grains can cause a spike in blood sugar that damages the body's ability to use insulin and process sugar.

For one study, Supriya Krishnan of the Boston University School of Public Health and colleagues studied more than 40,000 U.S. black women who filled out regular questionnaires every two years starting in 1995.

Over eight years, 1,938 of the women developed type 2 diabetes. The women who ate the most foods with a high glycemic index had a higher risk of diabetes.

But those who ate more fiber from whole grains had a lower risk. "Our results indicate that black women can reduce their risk of diabetes by eating a diet that is high in cereal fiber," Krishnan's team wrote.

Women who ate 5.9 grams of fiber a day or more had an 18 percent reduced risk of diabetes compared to the rest of the women, the researchers said.

"Incorporating fiber sources into the diet is relatively easy," they added.

"A simple change from white bread to whole wheat bread or substituting a cup of raisin bran or oatmeal for a cup of corn Chex or rice Chex will move a person from a low fiber intake category to a moderate intake category, with a corresponding 10 percent reduction in risk."

Plus, such whole grain foods have magnesium. which can lower blood pressure, they added.

For the second study, Raquel Villegas of Vanderbilt University in Nashville and colleagues followed a group of 64,000 Chinese women for an average of five years, interviewing them regularly about diet and other habits.

During the study, 1,608 of the women developed diabetes. Women who consumed more carbohydrates such as rice were more likely to develop diabetes.

Women who ate the most carbohydrates had a 28 percent higher risk of diabetes than the women who ate the least -- and those who ate the most bread, noodles and rice were 78 percent more likely to develop diabetes than those who ate the fewest carbs.

"Given that a large part of the world's population consumes rice and carbohydrates as the mainstay of their diets, these prospective data linking intake of refined carbohydrates to increased risk of type 2 diabetes mellitus may have substantial implications for public health," Villegas and colleagues wrote.

(Reporting by Maggie Fox; Editing by Will Dunham and Cynthia Osterman)