The Good, the Bad, and the Carbs

Can we just stop picking on carbs for a while? Perusing overheated headlines from a recent study in JAMA provides ample reasons to cool our passions on the topic.

In a 5-week, randomized, controlled study, Frank Sacks and colleagues found little support for the concept that a low glycemic index (G.I.) diet has superior health benefits compared to a high G.I. diet. In a four-way comparison, they contrasted the effects of low-carb versus high-carb and low G.I. versus high G.I. diets on cardiovascular and and metabolic risk factors like lipids, blood pressure, and insulin resistance.

The notion that some carbs are good and some carbs are bad is based in part on the concept of glycemic index. Those that cause smaller spikes in blood sugar levels are thought to be less problematic. Such foods tend to be higher in fiber. The health benefits of fiber, as the authors of this study concede, are well established.

Hyperbolic headlines from this study proclaimed that glycemic index is now “irrelevant” — providing a kind of equal and opposite reaction to stupid headlines about “toxic” carbs and sugar.

Blow away all the smoke, and what to we have? We have a short-term study that failed to find a benefit on markers for a long-term outcome. It’s not unusual. Such was the case with short-term studies of the benefits of fiber. As we learned with fiber, long-term studies provided a very different picture.

Nutrition research has many subtleties that don’t hold up well when they are twisted to support dogmatic beliefs. Arguments about virtuous and evil carbs are a case in point.

Click here to read more in the New York Times and here to read the study.

Low-Carb Chicago Dog, photograph © merlinmann / flickr

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