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Can brown rice slow the spread of type 2 diabetes?

January 3, 2012

The worldwide spike in type 2 diabetes in recent decades has paralleled a shift in diets away from staple foods rich in whole grains to highly refined carbohydrates, such as white rice and refined flours. Now, a group of researchers at Harvard School of Public Health (HSPH) aims to stem the tide by changing the color of the world’s rice bowl from white to more-nutritious brown.

To tackle the issue, the researchers launched the Global Nutritional and Epidemiologic Transition (GNET) Working Group, a collaborative initiative between researchers from the Departments of Epidemiology and Nutrition at HSPH and their colleagues in Asia, Latin America, and Africa. The aim of the group is to prevent the global diabetes epidemic by improving the carbohydrate quality of staple foods in the diets of people from around the world.

Refined carbohydrates like white rice have a high glycemic index, which causes rapid spikes in blood sugar that increase diabetes risk. Foods with a lower glycemic index, like brown rice, are digested more slowly, causing a lower and gentler change in blood sugar. But eating white rice and other refined carbohydrates such as white bread is now firmly embedded in many cultures around the world. In China, for example, highly polished white rice has come to be seen as a symbol of affluence and brown rice of poverty.

The GNET group began a study in Shanghai, China, in 2008 to see if participants could switch from white rice to brown. The preliminary results of that study, led by Frank Hu, professor of nutrition and epidemiology, were promising. This focus group study assessed the awareness and acceptability of brown rice in 32 Chinese adults, and examined the feasibility of introducing brown rice into the diet. Most participants consumed white rice daily and only a few had tried brown rice previously. Before tasting, most participants considered brown rice inferior to white rice in terms of taste and quality. However, after tasting brown rice and learning about its nutritional value, the majority indicated greater willingness to consume brown rice. In addition, most participants expressed willingness to participate in a future long-term brown rice intervention study.

In a subsequent pilot study, a total of 202 middle-aged adults were randomly assigned to white rice or brown rice groups and consumed the rice for 16 weeks. The study found a reasonably good compliance with the brown rice intervention. Although no overall differences in metabolic factors were found between the two groups, the brown rice intervention showed some benefits in improving HDL cholesterol and blood pressure in diabetic patients. The study demonstrated the feasibility of conducting long-term brown rice intervention trials in a Chinese population.

GNET pilot studies are now underway in eight additional countries—Costa Rica, India, Kenya, Kuwait, Mexico, Nigeria, Puerto Rico, and Tanzania—to assess the effect of substituting whole grains, including brown rice, for refined carbohydrate staples on blood pressure and blood sugar levels in populations at risk for diabetes, and to evaluate the acceptability of such interventions in local communities. The results of these studies will form the basis of longer-term interventions, which are likely to start in two years.

“Our hope is that this project will shift world trends in staple food consumption,” said Hannia Campos, senior lecturer on nutrition. “We expect that the project will impact food policy, production, and processing so that whole foods and legumes become the norm.” Campos has been encouraged by “the willingness of academics, government officials and even industry to recognize the importance of this initiative and to participate in the best way they can,” she said. “And, it’s been inspiring to see how willing middle-aged adults at high risk for the development of diabetes are to make these sorts of changes to improve their health.”

A conference organized by GNET at HSPH on November 14, 2011, drew scientists from around the world. View videos and slides from the presentations.

–Amy Roeder

Learn more

Replacing White Rice with Brown Rice or Other Whole Grains May Reduce Diabetes Risk (HSPH release)

Can Brown Rice Blunt An Epidemic? (Harvard Public Health Review)