Monday, 5 November 2012

Are Taubes and Couzens too hard on the Dietary Guidelines?

Gary Taubes and Cristin Kearns Couzens have a remarkable expose in Mother Jones of the sugar industry's misleading public information efforts over several decades.  The feature article stands out for its effective use of previously overlooked archival materials.  The indictment of sugar industry influence on policy advice and nutrition science research is devastating.

Everybody interested in U.S. food policy should read this story.

I do have one substantial complaint.  As in previous work by Taubes, this article does well in describing sugar industry public information campaigns, but it unfairly characterizes the recent editions of the Dietary Guidelines for Americans.

One of the best things about the 2010 Dietary Guidelines, for example, is that any reader can see the systematic evidence reviews -- published free on the internet -- that form the basis for the document's conclusions.

Here is what Taubes and Couzens say about the 2010 Dietary Guidelines:
The authors of the 2010 USDA dietary guidelines, for instance, cited two scientific reviews as evidence that sugary drinks don't make adults fat. The first was written by Sigrid Gibson, a nutrition consultant whose clients included the Sugar Bureau (England's version of the Sugar Association) and the World Sugar Research Organization (formerly the ISRF). The second review was authored by Carrie Ruxton, who served as research manager of the Sugar Bureau from 1995 to 2000.

But following the first link in the preceding paragraph, the federal government's evidence review says exactly the opposite of what Taubes and Couzens claim:
Conclusion.  A moderate body of epidemiologic evidence suggests that greater consumption of sugar-sweetened beverages is associated with increased body weight in adults.

Taubes and Couzens say USDA cited "two scientific reviews," but anybody following the link can see that USDA cited four reviews.  The review that USDA gives most weight was not mentioned by Taubes and Couzens, and it endorses the warnings against sugary drinks.

The whole advantage of systematic evidence reviews is to avoid cherry-picking evidence that favors one's own argument.  I think it would be great for science journalists to adopt the same practice of specifying a selection protocol in advance, just as the federal government's evidence reviews do, so that the journalists are not tempted to report only evidence that corroborates their thesis.

As this blog noted recently, the MyPlate guidance is accompanied by well-crafted terse advice about sugary drinks:

Drink water instead of sugary drinks.

Taubes and Couzens seem right on target in their criticism of the Sugar Association but quite unfair to the federal government and recent editions of the Dietary Guidelines.  (The authors' criticism of earlier editions may be more justified.)  Part of the reason I accept the main thrust of Taubes' critique of sugar-sweetened beverages is that -- despite his tone -- this particular aspect of Taubes' work seems fairly consistent with the sober judgement of mainstream dietary guidance in 2010.

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