(Reuters Health) - Among rice lovers, people who eat brown rice or other whole grains seem to have a lower risk of developing diabetes than those who eat white rice, Boston-based researchers said on Monday.
Among more than 197,000 US adults followed for up to 22 years, they found that eating more refined white rice was associated with a higher risk of type 2 diabetes, while eating more brown rice was associated with a lower risk of the disease.
Type 2 diabetes is characterized by high blood sugar levels caused by the body's inability to process sugar properly. The illness can sometimes be controlled through diet and exercise but may also require drugs.
"In general, the public should pay special attention to their carbohydrate intake and try to replace refined carbohydrates, including white rice, with whole grains," Dr. Qi Sun, of Harvard School of Public Health and Brigham and Women's Hospital, told Reuters Health by email. Current US dietary guidelines recommend that at least half of carbohydrates in the diet come from whole grains.
More Americans are eating rice, Sun and colleagues note in their report. According to the U.S. Department of Agriculture, rice consumption has shot up more than threefold since the 1930s. However, most of the rice eaten by Americans is refined white rice, which is stripped of its fiber, vitamins and minerals in the refining process and is more likely to fuel an increase in blood sugar after eating than its healthier whole grain cousin, brown rice.
The Boston team assessed rice intake and diabetes risk among nearly 40,000 men and more than 157,000 women in three long-running studies of doctors and nurses. Altogether, 10,507 of them developed type 2 diabetes during follow up.
Across all three studies, having more white rice in the diet was associated with an elevated risk of type 2 diabetes, the researchers report in the Archives of Internal Medicine.
When they pooled the data and took into account various diet and lifestyle factors that might influence the results, the doctors and nurses who ate the most white rice (at least 5 servings per week) had a significant 17 percent higher risk of developing diabetes than those who ate the least white rice (less than 1 serving a month).
In contrast, eating 2 or more servings of brown rice each week, as opposed to less than 1 serving a month, was associated with an 11 percent reduced risk of developing type 2 diabetes. Again, this was after accounting for other diet and lifestyle factors that might influence the results. The protective effect seen for higher brown rice consumption was "not dramatic, albeit significant," Sun said.
The researchers estimate that replacing one third of a serving of white rice daily (about 50 grams) with the same amount of brown rice could lower a person's risk of getting type 2 diabetes by 16 percent. They further estimate that replacing white rice with whole grains as a group could be associated with a risk reduction as great as 36 percent.
It's important to note that white rice contributed less than 2 percent of total calories for study subjects; brown rice less than 1 percent. Given that rice was not a significant part of the diet, there could be other reasons for the findings, the researchers acknowledge. But Sun pointed out that they adjusted for numerous factors that might influence the results and the findings still held up.
It's also possible that eating more brown rice is a marker for a healthier lifestyle. And, in fact, the brown rice eaters in the study did have a more health-conscious lifestyle and diet.
However, Sun said, "we adjusted for these factors including body adiposity (fat), smoking, physical activity, and other dietary factors, and the significant associations remained. This suggests that what we observed is unlikely the result of other factors."
The consistency of the results across all 3 studies also suggests that the findings are unlikely to be due to chance, Sun and colleagues note in their report.
Type 2 diabetes, which is closely linked to being overweight as well as poor diet and lack of exercise, is reaching epidemic levels. An estimated 8 percent of the U.S. population, and 180 million people around the world, now suffer from diabetes.
"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," Sun and colleagues conclude.
In addition to the study's funding by the U.S. National Institutes of Health, Sun is supported by a postdoctoral fellowship from Unilever Corporate Research. Unilever owns a number of food product brands