Because of differences in processing and nutrients, brown rice and white rice may have different effects on risk of type 2 diabetes mellitus. We examined white and brown rice consumption in relation to type 2 diabetes risk prospectively in the Health Professionals Follow-up Study and the Nurses' Health Study I and II.
We prospectively ascertained and updated diet, lifestyle practices, and disease status among 39 765 men and 157 463 women in these cohorts.
After multivariate adjustment for age and other lifestyle and dietary risk factors, higher intake of white rice (≥5 servings per week vs <1 per month) was associated with a higher risk of type 2 diabetes: pooled relative risk (95% confidence interval [CI]), 1.17 (1.02-1.36). In contrast, high brown rice intake (≥2 servings per week vs <1 per month) was associated with a lower risk of type 2 diabetes: pooled relative risk, 0.89 (95% CI, 0.81-0.97). We estimated that replacing 50 g/d (uncooked, equivalent to one-third serving per day) intake of white rice with the same amount of brown rice was associated with a 16% (95% CI, 9%-21%) lower risk of type 2 diabetes, whereas the same replacement with whole grains as a group was associated with a 36% (30%-42%) lower diabetes risk.
Substitution of whole grains, including brown rice, for white rice may lower risk of type 2 diabetes. These data support the recommendation that most carbohydrate intake should come from whole grains rather than refined grains to help prevent type 2 diabetes.
Rice has been a staple food in Asian countries for centuries. 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 (ie, brown rice) are removed to produce white rice that primarily consists of starchy endosperm. Although findings are not entirely consistent, consumption of white rice, in general, generates a stronger postprandial blood glucose response as measured by the glycemic index (GI) than the same amount of brown rice. A systematic review found that the mean (SD) GI was 64 (7) for white rice and 55 (5) for brown rice. Higher dietary GI has been consistently associated with elevated risk of type 2 diabetes (T2D) in prospective cohort studies. In addition, brown rice consumption may impart beneficial effects on T2D risk by virtue of its high content of multiple nutrients, such as fiber, vitamins, and minerals, the majority of which are lost during refining and milling processes. In line with these observations, high intake of white rice was associated with a monotonically elevated risk of developing T2D in a Chinese population, in which white rice consumption was the primary source of carbohydrate (74% of dietary glycemic load).
Compared with Asian countries, rice consumption is much lower in the United States but is increasing rapidly. According to the US Department of Agriculture 2009 food supply and disappearance data, rice consumption has increased more than 3-fold since the 1930s to reach 20.5 lbs (9.3 kg) per capita, and more than 70% of rice consumed is white rice. However, little is known about whether rice intake is associated with diabetes risk in US populations. We therefore evaluated the associations between intake of white rice and brown rice and risk of T2D in 3 large cohort studies with repeated prospective dietary assessments. We have previously observed an inverse association between whole grain consumption and risk of T2D in these cohorts. In the present study, we extended the follow-up of these previously reported studies and evaluated whether substituting whole grains for white rice is associated with a lower risk of diabetes.