Eating glutinous brown rice twice a day for 8 weeks improves glycemic control in Japanese patients with diabetes mellitus

Objective: We recently reported that eating glutinous brown rice (GBR) for 1 day improved the whole-day glucose profile and postprandial plasma glucose level compared with eating white rice (WR) or standard brown rice. However, it was unknown whether eating GBR could maintain improvement of glycemic control for a longer period. Therefore, we evaluated the effect of GBR intake for 8 weeks on glycemic control in outpatients with diabetes mellitus. Methods: This was an open-label randomized crossover study in outpatients with type 2 diabetes. Among the 18 subjects registered in this study, 2 were excluded from analysis. After a 1-week observation period while eating WR twice a day, the patients were randomly assigned to two groups. One group ate GBR as a staple food twice a day for 8 weeks and then switched to WR for the next 8 weeks, while the other group ate WR first and then switched to GBR. A mixed meal tolerance test was performed at baseline and after 8 and 16 weeks of dietary intervention to evaluate plasma glucose and serum C-peptide. Results: None of the subjects failed to complete the study because of disliking the taste of GBR. Hemoglobin A1c (7.5–7.2%, P=0.014) and glycoalbumin (20.4–19.4%, P=0.029) both decreased significantly when the patients were eating GBR. Additionally, the 30-min postprandial plasma glucose level (194–172 mg dl−1, P=0.031) and the incremental area under the concentration vs time curve of serum C-peptide (31.3–22.1 ng min ml−1, P=0.023) during the mixed meal tolerance test were also decreased significantly by intake of GBR. In contrast, there were no changes of glycemic control during the WR period. Conclusions: We confirmed that GBR was well tolerated for 8 weeks and improved glycemic control in patients with type 2 diabetes.