But Researchers Say Foods Like Bran Cereal and Oatmeal Can Reduce Risk of Type 2 Diabetes
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Reviewed By Louise Chang, MD
Nov. 26, 2007 -- Eating the right kind of carbohydrates may help lower the risk of type 2 diabetes, researchers say.
Two new studies suggest that eating simple or refined carbohydrates with a high glycemic index -- like white bread and rice -- raise the risk of type 2 diabetes. But eating whole grains like bran cereal and oatmeal can lower that risk.
The glycemic index measures the effect of carbohydrates on blood sugar levels. Foods with a high glycemic index, such as simple carbohydrates, cause a rapid rise and then decline in blood sugar levels; those with a low glycemic index, including whole grains, are absorbed more slowly into the bloodstream and have a more gradual effect on blood sugar levels.
The studies, published in the Archives of Internal Medicine, looked at the effects of carbohydrates on diabetes risk on two different groups of women.
Whole-Grain Cereal Fights Diabetes
The first study involved more than 40,000 African-American women in the U.S. During eight years of follow-up, nearly 2,000 of them developed type 2 diabetes.
The results showed that glycemic index was linked to increased risk of developing type 2 diabetes. African-American women who ate the most foods with a high glycemic index were more likely to develop type 2 diabetes that those who ate the least.
But cereal fiber was linked to a lower risk of diabetes. Women with the highest intake of cereal fiber had a lower risk of developing type 2 diabetes compared to those with the lowest intake.
"Our results indicate that black women can reduce their risk of diabetes by eating a diet that is high in cereal fiber," writes Supriya Krishnan, DSc, of Boston University School of Public Health, and colleagues. "Incorporating fiber sources into the diet is relatively easy: a simple change from white bread (two slices provides 1.2 grams of fiber) to whole-wheat bread (two slices provides 3.8 grams of fiber) or substituting a cup of raisin bran (5 to 8 grams of fiber) or oatmeal (4 grams of fiber) for a cup of corn chex (0.5 grams of fiber) or rice chex (0.3 grams of fiber) will move a person from a low fiber intake category to a moderate intake category, with a corresponding 10 percent reduction in risk."
Refined Carbs Raise Diabetes Risk
In the second study, researchers followed a group of nearly 65,000 Chinese women for about five years. During the study, 1,608 women developed diabetes.
The results showed women who consumed more carbohydrates were more likely to develop type 2 diabetes. Overall, women who ate the most carbohydrates had a 28% higher risk than those who ate the least.
The researchers also found that women who had diets with a higher glycemic index also had a higher risk of developing type 2 diabetes. In particular, women who ate 300 grams or more of rice per day were 78% more likely to develop type 2 diabetes than those who ate less than 200 grams per day.
"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," write researcher Raquel Villegas, PhD, of Vanderbilt University Medical Center, and colleagues.
SOURCES: Krishnan, S. Archives of Internal Medicine, Nov. 26, 2007; vol 167: pp 2304-2309. Villegas, R. Archives of Internal Medicine, Nov. 26, 2007; vol 167: pp 2310-2316. News release, American Medical Association.