Too much white rice a bane to endocrine health in South Asia

Eating higher amounts of white rice raises the risk of diabetes, and this association is especially pronounced in South Asia, a study has found. Meanwhile, in other regions of the world, the risk is modest or inconsequential.

“Overall, our findings are consistent with results from some of the previous studies conducted in Asia and Europe and North America, but not all,” according to the investigators, who pointed to the difference in rice consumption patterns across regions worldwide to explain the discrepancy. [BMJ 2012;344:e1454; Diabetes Res Clin Pract 2015;109:253-261; Eur J Nutr 2019;58:3349-3360; Ann Nutr Metab 2015;66:209-218; BMC Public Health 2017;17:133]

A region that consumes rice up to three times per week would not compare with the predominantly rice-eating populations, like South Asia, where intake levels average more than six cups of cooked rice per day, the investigators said. “Unmeasured confounding caused by other dietary factors, characteristics of the population, and ethnicity could also explain the discrepancy in these findings.”

The current analysis involved a large multiethnic, multinational cohort of 132,373 adults (mean age, 50 years) enrolled in the Prospective Urban Rural Epidemiology (PURE) study. These participants were enrolled from 21 counties, representing different geographies and continents—South Asia (India, Bangladesh, Pakistan), the rest of the world (Southeast Asia, Middle East, South America, North America/Europe, Africa), and China.

Overall, PURE participants consumed white rice at a median of 128 g/day, equivalent to less than one cup of cooked rice. South Asia logged the highest consumption level at 630 g/day (more than three cups), followed by Southeast Asia and China at 239 and 200 g/day (one to two cups), respectively.

Over a mean follow-up of 9.5 years, 6,129 individuals developed diabetes. This risk was 20 percent higher among those with the highest vs lowest intake categories of white rice (≥450 vs <150 g/day; hazard ratio [HR], 1.20, 95 percent confidence interval [CI], 1.02–1.40; p=0.003). [Diabetes Care 2020;doi:10.2337/dc19-2335]

Subgroup analysis showed that the diabetes risk associated with excessive white rice consumption was more pronounced in South Asia (HR, 1.61, 95 percent CI, 1.13–2.30; p=0.02) than in other regions of the world (HR, 1.41, 95 percent CI, 1.08–1.86; p=0.01). In China, there was no significant association (HR, 1.04, 95 percent CI, 0.77–1.40; p=0.38).

In the entire PURE population, individuals who consumed more than three cups vs less than one cup of cooked white rice daily were younger, had lower body mass index, and lower smoking rates—characteristics that likely reflected the profile of South Asians who had the highest consumption levels.

Additionally, the highest category of rice intake correlated with lower consumption of most other foods, such as whole and refined wheat products, fibre, red meat, and dairy products. Individuals who consumed more than three cups per day obtained the highest percent of their energy from carbohydrate and a lower percent from fat and protein.

Grain colour matters

Carbohydrate accounts for 70–80 percent of the calories consumed in most of South Asia. Earlier diets that consisted of mainly hand-pounded rice and other coarse grains like barley, rye, and maize have now been replaced by highly polished white rice in several countries. The polishing process strips the grains of dietary fibre, so it goes without saying that white rice is nutritionally inferior. [Indian J Med Res 2018;148:531-538; Int J Food Sci Nutr 2011;62:800-810]

Eating excessive amounts of rice is known to result in postprandial glucose spikes that, in turn, lead to compensatory hyperinsulinaemia to maintain blood sugar at normal levels. But the good news is that replacing white rice with unpolished brown rice cuts the glycaemic response by 23 percent and the fasting insulin response by 57 percent in overweight Asian Indians. [Diabetes Technol Ther 2014;16:317-325]

“However, the consumer acceptance of brown rice is poor, [owing to] longer cooking duration, decreased visual appeal, and greater difficulty in chewing the grain,” the investigators said. [J Am Coll Nutr 2013;32:50-57]

In cases where replacing polished white rice with other cereals or healthier varieties of rice cannot be done, the investigators suggested adding adequate legumes and pulses to reduce the glycaemic index (GI) of the meal and, possibly, to reduce the actual quantity of white rice consumed.

“All legumes, as a class, have a low GI and, thus, adding legumes to rice not only increases the fibre and protein content, but also lowers the GI of the rice-containing meal,” they explained. [J Nutr 2018;148:535-541]

“These may be important public health strategies to be adopted in South Asian and other populations with rice as the staple food, which, if combined with measures to increase physical activity, could help to slow down the rapidly rising epidemic of type 2 diabetes in these regions,” they said.