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Scientists at the Harvard School of Public Health performed a review of studies into whether there is an association between eating white rice and the risk of type 2 diabetes. Published in the BMJ, an association was confirmed for Asian populations in particular.
Dr Katarina Kos, Senior Lecturer and Honorary Consultant in Diabetes and Endocrinology, Peninsula College of Medicine & 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.
“At diabetes diagnosis patients are typically overweight if not obese and the risk of diabetes does not double but exponentially increase with BMI.
“As diabetes consultants we can only emphasise the need of weight management for the prevention of diabetes and weight loss as important part of Type 2 diabetes management.
“All of us should consider carefully whether we need a second helping e.g. when looking at the next serving of rice or any other carbohydrates in combination with what we are hoping to enjoy with it.”
Professor Shah Ebrahim, Professor of Public Health at the London School of Hygiene & Tropical Medicine, said:
“While the studies included in this review found an association between white rice consumption and diabetes in Asians, it would be wrong to consider it causal or to suggest that switching to brown rice would reduce the chances of getting diabetes.
“Out of 20 relevant studies they could only get data out of four of them which is likely to introduce bias.
“People who eat a lot of rice are likely to be bigger and/or wealthier than people who eat less so obesity and socio-economic position may be confounding these findings.”
Catherine Collins, Principal Dietician at St George’s Hospital, said:
“Whilst the dietary treatment of diabetes, obesity and related disorders benefits from slowly released sugars derived from ‘Low GI’ foods, evidence is conflicted on the impact of ‘High GI’ foods as a cause of these health conditions.
“The authors attempted to qualify the risk of developing Type 2 (non-insulin dependent) diabetes with white rice consumption, and presented a summary of studies deemed of suitable quality to examine this relationship.
“Not surprisingly, the Chinese and Japanese (Asian population) ate rice far more frequently than Western populations, often eating 3-4 portions of rice daily compared with one to two portions a week in the west.
“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 foods.
“Like other population studies, this analysis was weakened by the need to make assumptions regarding diet and population risk for diabetes. For example each portion of cooked rice – wherever eaten around the world – was deemed to weigh a very precise 158g (5.6oz) – this clearly contributes to inaccuracies in predictive analysis.
“Glycaemic Index was used in this review as relevant to its findings. However, the ‘GI’ of a food predicts blood sugar rise over a period of time when 50g of food carbohydrate is consumed. As white rice provides 26.4g of carbohydrate per 100g of rice, a ‘GI’ portion would be equivalent to a 190g serving of boiled rice. This was a larger portion than the predicted size used, so the predicted impact on blood sugar levels would be lower than estimated.
“In addition, the true GI of a carb rich food depends on how the rice is consumed. The addition of protein or fat to rice retards gastric emptying and lowers the GI, improviing glucose tolerance in those with diabetes.
“The use of traditional flavourings and foods such as vinegar, dairy products and soybean products in Asian cooking significantly reduces the GI of white rice to a level similar to that of wholegrain (brown) rice, further weakening the ‘high GI = increased risk of Type 2 diabetes’ link. This may well be the reason behind a lack of benefit in the results cited from Zhang and colleagues (cited reference 37). See also this nature paper.
“Finally, using statistical modelling to project diabetes risk from the Far East onto a Western population is fundamentally flawed. Rice is eaten in larger quantities and with different foods influencing GI compared to the west, and activity, lifestyle, genetic predisposition and other dietary factors also differ, making projections from one group to another less relevant.
“Does this study identify a link between increasing consumption of white rice and incidence of diabetes? Yes, in the Asian population.
“Would I agree that this risk could be transferred to our Western population as suggested by this analysis? Absolutely not – not only because of our lower consumption of rice overall, but also due to difference in diet and lifestyle – a fact borne out by the cited study of Hodge and colleagues, which demonstrated a lack of increased risk of diabetes across all intakes of white rice in an Australian population.”
Dr Glenys Jones, Nutritionist at MRC Human Nutrition Research 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 4 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.
“It is also not possible to determine that this relationship is true for all types of rice. The studies showed stronger associations in Asian populations, where for example the average daily rice intake was 4+ servings of white rice a day (625g+)with the study suggesting this may be due to the glycaemic load of white rice. However as the studies used did not obtain information on cooking methods (boiled or fried) or type of rice it is not possible to draw this conclusion, as different varieties of rice have different glycaemic values. For example short grain white rice has a higher glycaemic index than basmati rice.”
‘White rice consumption and risk of type 2 diabetes: meta-analysis and systematic review’ by Emily Hu et al., published in the BMJ on Thursday 15th March.