White Rice Consumption Linked to Type 2 Diabetes

Janis C. Kelly

March 19, 2012

March 19, 2012 — A meta-analysis and systematic review of summary data from studies on diet and type 2 diabetes risk has turned up a possible association between white rice consumption and diabetes, but limitations in the analysis preclude actionable conclusions.

The analysis of data from 4 studies, including 7 prospective cohort analyses in Asian (China and Japan) and Western (Australia and US) populations, was published online March 15 in the British Medical Journal by Emily A. Hu, from the Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts, and colleagues.

Using summary data from these studies, the authors conclude that the pooled relative risk for type 2 diabetes associated with highest vs lowest white rice intake was 1.55 (95% confidence interval [CI], 1.20 - 2.01) among Asian populations and 1.12 (95% CI, 0.94 - 1.33) in Western populations. The researchers conclude, "for each serving per day increment of white rice intake, the relative risk of type 2 diabetes was 1.11 ([95% CI,] 1.08-1.14) (P for linear trend<0.001)."

Interesting, but Few Immediate Implications

However, in an editorial also published online in the journal on March 15, Bruce Neal, MB, PhD, director of the George Institute for Global Health at the University of Sydney, Australia, warns against overinterpretation of the data: "Although the findings of the current study are interesting, they have few immediate implications for doctors, patients, or public health services and cannot support large scale action." Dr. Neal would like to see an analysis of the cohorts in the Hu study based on primary, rather than summary, data.

For each study, Hu and colleagues calculated risk ratios based on the highest vs lowest consumption of rice in that group. "However," Dr. Neal writes, "the highest and lowest levels of rice consumption varied greatly between studies. For example, in the primary analysis, a difference in consumption of 33 g/day (56 g/day vs 23 g/day) is plotted on the same scale as a difference in consumption of 250 g/day (750 g/day vs 500 g/day). Such massive differences in consumption are unlikely to produce the same effects on the risk of diabetes."

The 4 papers included 352,384 participants, with 13,284 incident cases of type 2 diabetes during follow-up periods ranging from 4 to 22 years.

The researchers suspect that white rice contributes to diabetes risk because of its high glycemic index (64) when compared with brown rice (55), whole wheat (41), or barley (25). "In addition, white rice is the primary contributor to dietary glycemic load for populations that consume rice as a staple food," they write.

The authors calculated a dose–response curve using the assumption that each serving was equivalent to 158 g of cooked rice. "For each serving per day increment of white rice consumption, the relative risk [of developing diabetes] was 1.11 ([95% CI,] 1.08 to 1.14, P for linear trend<0.001)...we estimated that 167 cases of diabetes per 100 000 middle aged people would occur each year for each serving per day increase in consumption of white rice."

Ideally, Dr. Neal would like to see incident diabetes investigated in a large, randomized controlled trial "in which white rice consumption is substantially modified in an intervention group," but he does not expect to see such studies any time soon.

"The real problem for the field of nutritional research is one of attracting the kind of resources that are available for the development of a promising drug treatment. Diet related ill health is now widely believed to be the leading cause of chronic disease around the world, but definitive research that precisely and reliably defines the effects of plausible, scalable, and affordable interventions is almost completely absent.... Until then, the effect of the consumption of white rice on the development of type 2 diabetes will remain unclear," Dr. Neal concludes.

The authors and Dr. Neal have disclosed no relevant financial relationships.

BMJ. Published online March 15, 2012. Article full text, Editorial extract

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