I mentioned yesterday that whenever something comes out saying that “everything you thought you knew about nutrition is wrong,” it’s a sign that some skepticism may be in order.

Here is another example: The article on the “sugar conspiracy“ by Ian Leslie published in The Guardian.  This strongly criticizes the work of Ancel Keys, whose work was largely but by no means exclusively responsible for the diet-heart hypothesis linking excessive intake of animal fats to heart disease risk.

I love conspiracy theories as much as anyone else and appreciated how the author made his case for this one.  My sense of his article was that it had grains of truth (Gary Taubes and Cristin Kearns, for example, report that Keys had funding from the sugar industry).  But the overall thrust of the article seemed excessively hyperbolic and based on selective picking of the data (cherry-picking).

Going through the piece line by line to identify errors and misinterpretations was not something I thought worth the trouble.

Fortunately, someone else did.

Katherine Docimo Pett, a master’s degree candidate in biochemical and molecular nutrition at Tufts University, who blogs as Nutrition Wonk, sent me her detailed critique of the paper.  She explains:

So I decided to look into the Seven Countries Study and I found a number of occasions where “The Sugar Conspiracy” misinterprets the evidence.  So buckle yourselves up, conspiracy theorists, because in this post, I’m going to cover the history of the diet-heart hypothesis – namely The Seven Countries Study and the subsequent research mentioned in “The Sugar Conspiracy.”

If you can wade through her lengthy analysis, you will be hard pressed to disagree with her conclusion:

In “The Sugar Conspiracy,” the author makes a lot of assumptions about intent, the usefulness of epidemiology, and even the conclusions of papers.  However, upon closer inspection, a lot of his evidence doesn’t hold up under scrutiny.

The idea that Keys claimed in his Seven Countries Study that correlation proved causation is false.  Keys just said that cholesterol is a mediator for heart disease and that saturated fat raises cholesterol, both of which later turned out to be true.  The Menotti “reanalysis” did not find that sugar is more closely correlated with heart disease than fat, and even if it did, it is a simple regression – it controlled for zero confounders, way fewer than were controlled for in the original Seven Countries Study.  Finally, there is plenty of evidence to suggest that substituting saturated fatty foods in favor of unsaturated fats is a good idea [Clarification: she must mean substituting unsaturated for saturated].

It is absolutely worthwhile to debate the merits of all scientific findings or even the merits of an entire field, like epidemiology.  Scientists, even nutrition scientists, do this all the time.  The problem, though, is that if basic facts are actually based on misinformation, you can’t build a real case for or against anything.

Amen.

Footnote: Sarah Tracy, an historian at the University of Oklahoma, has been working on a biography of Ancel Keys for quite some time.  I can’t wait for her to get it done (she probably can’t either), as it is likely to give us a thoughtful, balanced account of the significance of his work.

(c) Food Politics by Marion Nestle – Read entire story here.