Consuming more white rice appears to be associated with a higher risk for developing type 2 diabetes, whereas consuming more brown rice may be associated with a lower risk for the disease, according to a report in the June 14 issue of Archives of Internal Medicine, one of the JAMA/Archives journals.
"Rice has been a staple food in Asian countries for centuries," the authors write as background information in the article. "By the 20th century, the advance of grain-processing technology made large-scale production of refined grains possible. Through refining processes, the outer bran and germ portions of intact rice grains (i.e., brown rice) are removed to produce white rice that primarily consists of starchy endosperm." U.S. rice consumption is lower than that in Asian countries but is increasing rapidly, and more than 70 percent of the rice consumed is white.
Qi Sun, M.D., Sc.D., of Harvard School of Public Health, Boston, and colleagues assessed rice consumption and diabetes risk among 39,765 men and 157,463 women in three large studies: the Health Professionals Follow-Up Study and the Nurses' Health Study I and II.
After adjusting for age and other lifestyle and dietary risk factors, those who consumed five or more servings of white rice per week had a 17 percent increased risk of diabetes compared with those who consumed less than one serving per month. In contrast, eating two or more servings of brown rice per week was associated with an 11 percent reduced risk of developing type 2 diabetes than eating less than one serving per month.
Based on the results, the researchers estimated that replacing 50 grams (equivalent to one-third of a serving) of white rice per day with the same amount of brown rice would be associated with a 16 percent lower risk of type 2 diabetes. Replacing white rice with whole grains as a group could be associated with a risk reduction as great as 36 percent.
In general, white rice has a higher glycemic index—a measure of how much a food raises blood glucose levels compared with the same amount of glucose or white bread—than brown rice, the authors note. "The high glycemic index of white rice consumption is likely the consequence of disrupting the physical and botanical structure of rice grains during the refining process, in which almost all the bran and some of the germ are removed," they write. "The other consequence of the refining process includes loss of fiber, vitamins, magnesium and other minerals, lignans, phytoestrogens and phytic acid, many of which may be protective factors for diabetes risk."
The current Dietary Guidelines for Americans recommend that at least half of carbohydrate intake come from whole grains. "From a public health point of view, replacing refined grains such as white rice by whole grains, including brown rice, should be recommended to facilitate the prevention of type 2 diabetes," the authors conclude.
(Arch Intern Med. 2010;170:961-969. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: This study was supported by research grants from the National Institutes of Health. Dr. Sun is supported by a postdoctoral fellowship from Unilever Corporate Research. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.
Archives of Internal Medicine