New Study: Beef Bests Beans for Health! (N.B. check the fine print…)

That’s the headline. Here’s the study.

Five Mongolian yak herders are randomly assigned to a diet of either beef jerky, or jellybeans, for 72 hours (note that our headline did not specify what kind of beans!). The test for overall health at the end of that intervention is the effort required, by a dental hygienist-in-training, to pull out all of the participants’ teeth with a pair of pliers. The study is double-blinded because both the yak herders and the student closed their eyes during the extraction of teeth.

As fate would have it, the student pulled out all the teeth of the jellybean group (two members) first, and only after, those of the three people in the beef jerky group- by which time, her hands were getting tired (and frozen). She thus found it subjectively “harder” to pull out the teeth of the beef jerky group, and voila: beef beats beans!

Yes, of course I made up all of this nonsense. But it’s shockingly, alarmingly close to what actually passes for information exchange in the world of nutrition these days.

The particular provocation of this jeremiad was a comment in response to a recent, prior column of mine nominally related to dietary fat. A correspondent challenged my position on dietary fat (i.e., my position is that diets can be high, low, or in-between in total fat, and be good, bad, or ugly based on the actual assembly of foods) by trotting out the results of a PREDIMED trial that purportedly showed how a Mediterranean diet bested a low-fat diet.

To be clear, I am a fan of both PREDIMED, and Mediterranean diets. As for PREDIMED, some of the lead researchers involved are colleagues and friends of mine. My own diet is, in fact, Mediterranean- as is my wife, who is the very talented architect of it. Catherine grew up in southern France, and our diet has always been infused by those Provencal inclinations.

I am not, however, a fan of straw man arguments, garbage in/garbage out studies, or hyperbolic headlines. My Mongolian bean study may exaggerate these liabilities a bit, but alas, not all that much.

In the case of the PREDIMED trial in question, the so-called, and oft-repeated “low fat” diet was nothing of the sort; it was the control group. As the authors themselves say: “or a control diet (advice to reduce dietary fat).” In other words, there was no attempt here- not even a feigned attempt- to compare an optimal Mediterranean diet to an optimal whole food, plant-based, low-fat diet- the kind that has been shown, consistently, to do stunningly good things for health. Rather, “advice to reduce dietary fat” was, effectively, the non-intervention group. Predictably, this group changed their diets from baseline almost not at all. Specifically, their total fat intake went from a mean of 39% of calories at baseline to 37% of calories at the end of the trial (see Table S7, p. 28 of the Supplementary Appendix- which, if you have an opinion about this study, you surely read already…).

I trust we can agree- no matter what diet you practice, no matter what dietary ideology you espouse- that a study of a diet nudged from 39% fat to 37% fat qualifies in NO way whatsoever as a study of a “low fat” diet. But as a culture, we are so committed to a never ending game of diet-science Ping Pong, that this paper spawned headlines like: Mediterranean Diet Beats Low-Fat For Heart Health in Big New Study. Seriously.

And then, that absurd misrepresentation turns into echoes in cyberspace. Those echoes are in turn heard, and repeated, by a much larger population that never looked at the original study, and those echoes in turn generate echoes that are heard and repeated. Flash forward a couple of years, and my reasonable correspondent (a health care professional) cites this study as evidence for something it not only did not show, but was not even designed to show. But the damage has been done- it’s urban legend now. Argue back- no, the Mediterranean diet, excellent as it is, did NOT beat a “low fat” diet- and the high-fat mafia beats you over the head with salamis, and accuses you of working for Snackwells.

My point? No amount of science will amount to a hill of beans if we don’t approach it with some modicum of sense. No meaningful understanding about diet will be advanced if we misrepresent what studies show, and then endlessly repeat those misrepresentations. Dogma is a very sorry substitute for dialogue; and headline hyperbole is a very poor approximation of what studies actually mean.

My recommendation is to steer well clear of any dental hygiene students with eyes closed and pliers in hand- and chew on that. Watch out for steaming piles of yak poop while you are at it.

-fin

David L. Katz, MD, MPH, FACPM, FACP, FACLM

Director, Yale University Prevention Research Center; Griffin Hospital
President, American College of Lifestyle Medicine

Founder, The True Health Initiative

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