Why are Asian-Americans at higher risk for developing type 2 diabetes than Caucasian Americans, and prone to developing the disease at lower body weights? One part of this puzzle may lie in the transition from the traditional high-fiber, low-fat Asian diet to the typical low-fiber, high-fat Westernized diet, which may pose extra risks for those of Asian heritage, according to a small study conducted by Harvard Medical School researchers at the Joslin Diabetes Center.
The randomized clinical trial demonstrated that both Asian-Americans and Caucasian Americans at risk of type 2 diabetes who adopted a rigorously controlled traditional Asian diet lowered their insulin resistance. A leading risk factor for developing diabetes, insulin resistance is a condition in which the body struggles to use the hormone insulin, which helps to metabolize sugar.
When both groups of participants switched from a traditional Asian diet to consuming typical Western fare, the Asian-Americans experienced greater increases in insulin resistance than the Caucasian Americans did, said George King, HMS professor of medicine at Joslin. He is senior author of the paper published in the journal PLOS One.
The 16-week pilot trial was completed by 24 East Asian Americans (Chinese, Japanese or Korean) and 16 Caucasian Americans, whose average age was 34. They were either of normal weight or overweight, but not obese. All the volunteers had a family history of type 2 diabetes or another indication of diabetes risk, such as gestational diabetes.
For the first eight weeks, all participants ate a traditional high-fiber Asian diet with 70 percent of calories from carbohydrates, 15 percent from protein and 15 percent from fat, providing 15 grams of fiber per 1,000 calories. The food was freshly prepared by local chefs and delivered every two days. “Three meals and one snack were included each day, and we made sure that they were nutritious as well as very tasty,” says Ka Hei Karen Lau, a Joslin dietitian and certified diabetes educator.
For the second eight weeks, 33 of the volunteers (20 Asian-Americans and 13 Caucasian Americans) transitioned to a typical low-fiber Western diet with 50 percent of calories from carbohydrates, 16 percent from protein and 34 percent from fat, and providing 6 grams of fiber per 1,000 calories. Seven volunteers (4 Asian-Americans and 3 Caucasian Americans) stayed on the traditional Asian diet to act as controls for the study.
Meeting with the trial participants every two weeks, the Joslin team adjusted individual diets as needed to keep their weights relatively steady, so that changes in their metabolism were not driven primarily by changes in weight.
Maintaining those steady body weights for trial participants was a challenge, King said. “It was almost impossible to prevent people from losing weight on the Asian diet, and that was not because the food wasn’t good,” he said. “Almost everybody gained weight on the Western diet, and we had to work very hard so they didn’t gain too much.”
The researchers suggested that the combination of high fiber and low fat in the traditional diet may help to explain the decrease in insulin resistance, especially for the Asian-American participants.
Additionally, those on the traditional Asian diet lowered their LDL, or “bad,” cholesterol, a potential benefit for cardiovascular health.
“These results were very exciting for Asian-Americans,” Lau said. “We are at high risk for diabetes, but we can use diet to help prevent it.”
Joslin’s Asian Clinic now promotes a traditional Asian diet and shares suitable recipes with patients.
The researchers hope to follow up the pilot trial with a larger trial that compares results of a traditional Asian diet with a Westernized Asian diet and does not try to control participant weight.
Asian-Americans have about a 20 percent higher risk of developing type 2 diabetes than Caucasian Americans do. More than half of the adults in the world with the disease live in Southeast Asia and the Western Pacific, the researchers pointed out, and about 10 percent of adults in China now suffer from diabetes.
Adapted from a Joslin news release.
