White rice joins the growing list of refined carbohydrates with links to increased risks for diabetes, according to a new large study that quantified odds for consumers of white rice—as well as brown rice.

Turning brown rice white entails removing a rice grain's bran and germ, which uncovers the white endosperm. The process also raises the grain's glycemic index (a measure of a carbohydrate's ability to raise blood sugar) and strips away vitamins, fiber, magnesium and other components that might help keep diabetes at bay.

The new findings have key health implications because more than 70 percent of rice eaten in the U.S. is white rice, noted the authors of the new study, led by Qi Sun of the Department of Nutrition at the Harvard School of Public Health. The findings were published online June 14 in Archives of Internal Medicine.

Assessing the reported health, dietary and lifestyle habits of 197,228 U.S. adults (from the Health Professionals Follow-up Study and the Nurses' Health Study I and II cohorts), the researchers found a striking difference in rates of type 2 diabetes between those who ate a lot of white rice and those who consumed more brown rice. Even after controlling for age, lifestyle, diet, ethnicity and other variables, the researchers still found a significant difference in risk.

Those who consumed at least five servings (150 grams each) of white rice per week had a 17 percent higher risk of getting type 2 diabetes than those who hardly ate any white rice at all. And people who were eating at least two servings of brown rice a week had an 11 percent lower chance of getting the disease than those who ate less than one serving of it a month. The authors calculated that replacing white with brown rice would lower the chances of type 2 diabetes by 16 percent.

Brown rice, however, did not appear to be the most effective whole grain for fending off diabetes. The researchers found that substituting about 50 grams other whole grains (such as whole wheat or barley) for that much of (uncooked) white rice each day could reduce diabetes risk by as much as 36 percent.

Although rice currently makes up a small portion of most U.S. diets (generally less than two percent of total daily energy intake), in other parts of the world, such as Japan, rice can be responsible for nearly 30 percent of daily average energy intake, Sun and his colleagues noted. Nevertheless, the researchers concluded in their paper, "From a public health point of view, replacing refined grains such as white rice by whole grains, including brown rice, should be recommended" to help prevent type 2 diabetes.

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