Consumption of white rice appears to increase the risk of developing type 2 diabetes, whereas consumption of brown rice appears to decrease that risk, according to a report based on data from three studies.
“From a public health point of view, replacing refined grains such as white rice [with] whole grains, including brown rice, should be recommended to facilitate the prevention of type 2 diabetes,” said Dr. Qi Sun of the Harvard School of Public Health, Boston, and associates.
White rice is known to have a higher glycemic index than than that of brown rice. The consumption of white rice in the United States has more than tripled since the 1930s.
White rice's relationship to type 2 diabetes has been studied in several Asian countries, where it is a staple accounting for as much as 75% of the diet. But this is the first prospective study to specifically assess the relationship between the disease and the intake of both white and brown rice in a Western population, where white rice accounts for approximately 2% of the diet, Dr. Sun and his colleagues noted.
The researchers used data from three large cohort studies that documented food intake to examine this association, assessing diet and diabetes status in 39,765 men in the HPFS (Health Professionals Follow-Up Study), 69,120 women in the NHS I (Nurses' Health Study I), and 88,343 women in the NHS II.
There were 2,648 incident cases of diabetes during 20 years of follow-up in the HPFS, 5,500 cases during 22 years of follow-up in the NHS I, and 2,359 cases during 14 years of follow-up in the NHS II, Dr. Sun and his colleagues reported.
Greater consumption of white rice was associated with a higher risk of diabetes across all three studies. This association was attenuated after the data were adjusted to account for multiple lifestyle and dietary risk factors, “but a trend of increased risk associated with high white rice intake remained,” the investigators said.
“In comparison with those in the lowest category of white rice intake, participants who had at least five servings of white rice per week had a 17% higher risk of developing type 2 diabetes,” they said (Arch. Intern. Med. 2010;170:961-9).
In contrast, greater consumption of brown rice was associated with a lower risk of diabetes. This association was attenuated but still remained significant after the data were adjusted to account for lifestyle and dietary risk factors.
“When compared with the participants who ate less than 1 serving of brown rice per month, the pooled risk reduction of type 2 diabetes was 0.89 for intake of 2 or more servings per week,” Dr. Sun and colleagues said.
“Because brown rice consumption levels were rather low in our participants, we could not determine whether brown rice intake at much higher levels is associated with a further reduction of diabetes risk,” they added.
The researchers then assessed the relative risks associated with replacing one-third of a serving of white rice per day with the same amount of brown rice. “In all three cohorts, substituting brown rice for white rice was consistently associated with a lower risk of type 2 diabetes.” Every 50-g substitution of brown rice for white per day was associated with a 0.84 risk reduction.
The study evaluated the association between diet and diabetes among working, highly educated health professionals of predominantly European ancestry. The findings may not be generalizable to other populations, Dr. Sun and associates said.
Disclosures: The study was supported by a grant from the National Institutes of Health. Dr. Sun is supported by Unilever Corporate Research. No financial conflicts of interest were reported.
Substituting brown rice for white was consistently associated with a lower risk for type 2 diabetes.
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