Improve glucose control with brown rice

A randomized, controlled trial conducted in India, which has the second greatest number of people living with Type 2 diabetes in the world, suggests that choosing brown rice instead of white rice may help those with metabolic syndrome improve their glucose control (Brit J Nutr 2019;121:1389-1397).

The HbA1c score is a test that evaluates glucose scores over the long term - about the previous 3 months. Those who do not have diabetes will have a score between 4% and about 5.5%. If your score is higher than that but does not reach 6.4%, you're considered "pre-diabetic," and those with HbA1c scores over 6.5% are considered to have diabetes. It's important for diabetics to maintain good long-term control of their glucose scores, and the goal for most diabetics is a HbA1c score under 7%. Scores over 7% put you at a greater risk of complications from diabetes.

In this study, organized by researchers from Harvard Medical School as well as those affiliated with the Madras Diabetes Research Foundation in India, participants were recruited from patients of the Research Foundation for a 6-month crossover feeding trial. To qualify for the study, these Indian patients had to be between 25 and 65 years of age, have a BMI of at least 23 (clinically overweight for their ethnicity) and not have elevated glucose scores, diagnosed diabetes, coronary artery disease, stroke, cancer, or a number of other conditions that might affect glucose scores.

At that start of the study the participants had their height and weight measured in the clinic and responded to demographic and healthy history questionnaires. They were then randomly assigned to one of two groups.

For 3 months, both groups reported to the clinic 6 out of 7 days per week, receiving 2 out of 3 meals per day from the clinic. Half of the participants received white rice with their meals, while the other half received brown rice with their meals.

After the initial 3-month period, the participants returned to their usual diets for two weeks, then switched diets for the following 3 months: those who had been receiving white rice for the initial 3 months were served brown rice for 3 months, and vice versa.

Each participant was weighed and their waist circumference measured on a monthly basis throughout the 6+-month study. As well, blood pressures and body fat percentage was recorded and the participants also responded to dietary questionnaires regarding the meals they ate outside the lab.

A total of 112 men and women completed the entire 6-month feeding study. Fully 68% of those participants were clinically considered to have pre-diabetes, and 40% had metabolic syndrome (a condition where an individual has 3 of the 5 following components: elevated waist circumference, low HDL cholesterol, high triglyceride scores, high blood pressures, or poor fasting glucose scores).

The authors found that during the period the participants consumed brown rice in the lab, participants tended to have lower blood glucose, insulin, HbA1c scores, triglycerides, total cholesterol scores, and LDL cholesterol, although these results were not considered clinically significant. However, those participants who had been identified as having metabolic syndrome at the start of the study saw their HbA1c scores decline by 0.18 - which may be a clinically significant amount depending on the individuals' HbA1c levels at the start of the study.

What this means for you

According to previous research, Indians living in the region where this study was conducted consume "nearly half of daily energy intake... from refined grains" - and white rice constitutes fully 75% of those refined grains. Switching to brown rice for two meals per day would be a big change in their diet, with the biggest difference in the amount of fiber consumed, not to mention the other vitamins and minerals that are present in greater amounts in brown rice vs. white rice.

This does support the effects of whole grains on metabolic scores in general and on HbA1c in particular.

First posted: August 14, 2019