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Putting rice-diabetes findings into perspective

These kinds of observational prospective studies can show only a correlation between two things, not a causation.

Is white rice quite so deadly as recent studies lead one to believe?

Hmmm. … What to do about rice?

In recent months we’ve been told that brown rice is more likely than white rice to contain arsenic, a chemical toxin.

And now along comes a study that suggests eating white rice raises your risk of developing type 2 diabetes.

Sometimes, figuring out what to have for dinner seems way too complicated.

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But before you give up on rice altogether, let’s try to put these latest findings into some kind of perspective. As an expert has already mentioned in this column, the concern over brown rice is really more about brown rice sweeteners, which seem to concentrate any absorbed arsenic, than the whole grain itself.

So, until we know more, avoiding food products with brown-rice sweeteners and eating brown rice in moderation appears to be the key message there.

And what about white rice and diabetes?

Well, that seems to be a matter of understanding the difference between correlation and causation.

Details, details

The new study linking white rice and diabetes was published Friday in BMJ (formerly known as the British Medical Journal). A team of researchers from the Harvard School of Public Health and related institutions wanted to investigate white rice’s high glycemic load — its propensity to raise a person’s blood sugar levels after it’s digested. Some past research has found an association between high-glycemic diets and an increased risk of developing type 2 diabetes.

But findings from past studies on white rice and type 2 diabetes have had mixed results, with some showing an association and others not. The Harvard researchers decided to pull together data from the best studies on the topic to create a meta-analysis. Using some strict criteria, they narrowed those studies down to four — one each from China, Japan, the United States and Australia — involving 352,384 individuals. All four studies were prospective, which means that they recruited people without diabetes who were then followed to see if they did develop the disease. The length of this follow-up ranged from four to 22 years.

After analyzing the data, the researchers determined that 13,284 of the individuals in these studies — or 4 percent — developed type 2 diabetes. A further crunching of the numbers led them to report that those people in the study who ate the highest amounts of white rice were 27 percent more likely to develop diabetes than those who ate the lowest amounts. Furthermore, each daily serving of rice increased the diabetes risk by 11 percent.

But the increased risk was only significant among the Asian populations. Asian participants with a high rice intake were found to have a 55 percent greater risk of developing type 2 diabetes than their low-rice-consuming peers. No significant association between white rice consumption and type 2 diabetes risk was found in the two Western studies.

The fact that the meta-analysis’ key finding was not consistent across all the population groups raises questions about its usefulness.

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Interesting, but far from conclusive

As always, it’s important to remember that these kinds of observational prospective studies can show only a correlation between two things, not a causation. Other factors, not identified in the study, could be behind the higher risk for diabetes among the white-rice eaters. And indeed, as Canadian family physician and Weighty Matters blogger Yoni Freehoff has pointed out in his scathing critique of the meta-analysis, “this study’s conclusions failed to consider incredibly relevant diabetes confounders like family history of diabetes, socioeconomic status, and dietary consumption patterns, including the dietary consumption of other categories of refined grains.”

That failure, he adds, “makes quantifying the effect on diabetes development due to white rice consumption from this data set impossible.”

An editorial that accompanied the BMJ meta-analysis says essentially the same thing (although a bit more kindly): “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. Further research is needed to develop and substantiate the research hypothesis.”

So, you can, for the time being at least, ignore the more sensational headlines (“White Rice Increases Diabetes Risk”) and take this study’s findings with a grain of, well, rice.