Eating white rice may be linked to a higher risk of Type 2 diabetes, researchers have said.
A review of four studies involving around 350,000 people found the more white rice people ate, the higher their chance of developing the condition seemed to be.
Experts from Harvard School of Public Health and Harvard Medical School looked at two studies in Asian people (Chinese and Japanese) and two in Western populations (the US and Australia).
Asian people tended to have a much higher white rice intake than those in the West, averaging three to four servings a day compared with one or two servings per week.
The results showed that Asian people have a higher chance of developing Type 2 diabetes, with those who ate the most at highest risk.
But even for Western populations with typically low intakes, the researchers said "relatively high white rice consumption may still modestly increase risk of diabetes".
In the total population, the experts said that for every extra serving of white rice (assuming 158g per serving), the risk of Type 2 diabetes increased by about 11%.
Writing in the British Medical Journal, the authors concluded: "We found that higher white rice consumption was associated with a significantly elevated risk of Type 2 diabetes. This association seems to be stronger for Asians than for Western populations."
The studies took into account a variety of factors such as people's weight, how much exercise they took and dietary issues such as red meat and alcohol intake.
All the people were free from diabetes at the start of the studies.
During follow-up, ranging from four to 22 years, around 13,200 people developed diabetes.
The authors said previous studies suggest that eating brown rice may modestly decrease the risk of Type 2 diabetes. But they said larger studies were needed to look at any benefits of substituting brown rice for white rice.
In an accompanying editorial, Dr Bruce Neal from the University of Sydney said more, bigger studies were needed on the issue.
Dr Glenys Jones, nutritionist at the Medical Research Council's Human Nutrition Research centre in Cambridge, said: "It is important to note that this study does not show or prove that white rice consumption causes diabetes but is an analysis of four observational studies which, when combined, showed that those with the higher rice intakes were associated with higher reported diabetes incidences.
"However, from these studies it cannot be concluded that the increased diabetes incidence occurred because of the higher rice intakes and could be due to other lifestyle factors."
Catherine Collins, principal dietician at St George's Hospital in London, said: "The review findings suggested that the risk of developing Type 2 diabetes was higher in the Asian population but whether this was due to higher daily intakes of rice or to genetic predisposition couldn't be determined from this research, despite attempts by the authors to imply a correlation of diabetes risk with large intakes of high GI (glycaemic index) foods."
About 2.5 million people in the UK are diagnosed with Type 2 diabetes, and another 850,000 have the condition but do not know it.
Dr Iain Frame, director of research at Diabetes UK, said: "This new study is a review of previous research looking at the association between white rice consumption and Type 2 diabetes, but it has not looked at whether eating lots of white rice actually increases risk of Type 2 diabetes.
"Previous research in this area has not provided conclusive results and it is a difficult area to conduct research because no single type of food is directly linked or associated with the development of Type 2 diabetes.
"So this study does not provide any strong evidence that eating lots of white rice will put people at increased risk of Type 2 diabetes."
Dr Katarina Kos, honorary consultant in diabetes and endocrinology at the Peninsula College of Medicine and Dentistry, said: "The authors found that with each serving of white rice the relative risk of Type 2 diabetes increases.
"Rice is the typical carbohydrate which accompanies meals, especially in Asian populations.
"The more rice/starchy food we have, the more likely we will also eat more of everything else."
She added: "As diabetes consultants, we can only emphasise the need of weight management for the prevention of diabetes and weight loss as an important part of Type 2 diabetes management.
"All of us should consider carefully whether we need a second helping - for example, when looking at the next serving of rice or any other carbohydrates in combination with what we are hoping to enjoy with it."
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