Epidemiologic studies have suggested that higher consumption of white rice (WR) is associated with increased risk for type 2 diabetes mellitus. However, it is unclear whether substituting brown rice (BR) for WR can improve metabolic risk factors. A total of 202 middle-aged adults with diabetes or a high risk for diabetes were randomly assigned to a WR (n = 101) or BR group (n = 101) and consumed the rice ad libitum for 16 wk. Metabolic risk markers, including BMI, waist circumference, blood pressure, glycated hemoglobin, and serum lipid, glucose, and insulin concentrations were measured before and after the intervention. Over the course of the intervention, no between-group differences were found for any markers except the serum LDL cholesterol concentration, which decreased more in the WR group compared to the BR group (P = 0.02). However, this effect was observed only among participants with diabetes (n = 47). The reversion rate of reduced serum HDL cholesterol was marginally higher in the BR group (14.9%) than in the WR group (6.9%) (P = 0.07). Among participants with diabetes, a greater reduction in diastolic blood pressure was observed in the BR group compared to the WR group (P = 0.02). Our study suggests that incorporating BR into the daily diet for 16 wk did not substantially improve metabolic risk factors. Further studies with larger sample sizes, longer durations of follow-up, and different varieties of rice are needed to carefully examine the role of BR in the prevention and management of diabetes.
Trial registration: ClinicalTrials.gov NCT01022411.