There has been renewed interest on the link between eating rice and the risk of diabetes.
Focus on diabetes is not new in Singapore. Furthermore, debate about the association of glycaemic index (GI) to Type 2 diabetes (T2D) has been going on for decades.
The GI was introduced more than 30 years ago as a ranking of carbohydrates according to their effect on blood glucose responses. GI depends on the type and amount of carbohydrate consumed.
Recently, consuming white rice has been singled out as a culprit in increasing diabetes risk.
This is based on a Harvard pooled-analysis published in the British Medical Journal in 2012. Before this, the association between white rice consumption and risk of T2D had been examined in both Asian and Western populations, but the findings were not consistent across studies.
The Harvard analysis of four studies suggested that higher white rice consumption is associated with increased risk of developing T2D. However, the study was unable to evaluate the effects of substituting brown rice for white rice.
An obvious inference from such a study would be to reduce the intake of carbohydrates in one's diet. There is no firm basis to recommend brown rice instead so as to reduce the risk of T2D.
GI is useful when evaluating the glucose response of single-carbohydrate foods. But it is less obvious when combinations of carbohydrate-rich foods, mixed meals or even whole diets are evaluated. People do not consume carbohydrates such as rice on their own. The addition of protein and fat reduces the glycaemic response to carbohydrates such as potatoes and rice. In Singapore, rice or another carbohydrate is consumed with protein and fat, for example, chicken rice or fried rice.
While the same amount of brown rice may have a lower GI of 65, compared with polished white rice's GI of 80, studies show that different responses to co-ingestion of protein and fat reduced the difference between the glycaemic responses to the two carbohydrates.
Indeed, studies have randomly assigned people to high- and low-GI diets of the same calorie levels for up to six months. Such energy-restricted diets helped people lose weight. But there is no difference in measures of insulin function and resistance between the high- and low-GI diets.
Wee Shiou Liang (Dr)