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My Cousin Vinny's Diet

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

Originally published by David L. Katz, MD, MPH, FACPM, FACP, FACLM on LinkedIn: My Cousin Vinny's Diet

As I trust most of you know, My Cousin Vinny is a terrific movie. If you haven’t seen it, I certainly recommend it. The characters are indelible; the dialogue is terrific; the courtroom tension and the comedic absurdity, both dosed perfectly; and in the end, the good guys…well, I don’t want to spoil it.

For today’s purposes, my interest is limited to this scene that takes place in a jail cell, as Vinny explains to his cousin/client, the defendant, how compelling the prosecution case can seem and yet be wrong. Of course, they both know the prosecution is wrong- as does the audience- because the defendant is innocent.

I thought of this not long after seeing a video of a recent talk at the Zurich Heart House, sent to me by a colleague, in which a prominent cardiology researcher- known mostly for studies of pharmacotherapy- contends that meat is protective against heart disease, fish is neutral, and vegetables useless. You can look into the researcher’s platform here, but I can’t seem to share the YouTube video. It is no longer accessible, which seems to suggest that somebody other than me found more than a bit amiss with it.

Before debunking this obvious nonsense, let’s revisit with Vinny. The prosecution in that trial was wrong, but not unreasonable; incorrect, but not insincere. I am inclined to say the same of Dr. Yusuf, whose overall body of work I very much appreciate. However, in the no-longer-accessible-video, he starts out by noting that he is not expert in nutrition. That’s an odd beginning for a rant against just about every contention predicated on the weight of scientific evidence, and common sense in that very field. It would be as if the attorneys opposing Vinny started out declaring no actual expertise in criminal law. 

But leaving out the oddity of self-disqualification, Dr. Yusuf’s argument – that carbohydrate causes heart disease, fat is protective, vegetables are of no help, fish is neutral, and meat is beneficial - is very much like the prosecution case as Vinny characterizes it. Convincing, through legerdemain- but unequivocally wrong.

The irony is that Dr. Yusuf’s own published work, and his own published assertions about trial design, contribute mightily to the rebuttal.

The study discussed at the Zurich Heart House by Dr. Yusuf last week- the INTERHEART Study- does, indeed, involve some 150,000 people from 17 countries. But, it is a case-control study. 

I suspect most people celebrating the talk’s invitation to consume more pepperoni don’t know what that implies, but as someone who has authored textbooks on the matter, I do. This is one of the weakest forms of epidemiologic research, prone to many interpretation errors, subject to many forms of bias, useful for generating but not testing hypotheses, and utterly useless for establishing cause-and-effect. This is fact, acknowledged by all who are trained in epidemiology. More interesting, it is a position Dr. Yusuf has himself advanced, arguing the need for large, simple randomized trials to avoid just such pitfalls.

Of course, there are large, randomized trials showing what dietary patterns defend against heart disease and death- again and again- and they refute the position taken by Dr. Yusuf in his very odd, recent talk. Predictably, perhaps, he made no mention of them.

But that is far from the most damning argument in Dr. Yusuf’s own body of work against the errant conclusions in the Zurich talk. Consider, for instance, this paper of his about the INTERHEART Study, published in the New England Journal of Medicine in 2014. The abstract states the case in language perfectly clear to scientist and non-scientist alike: cardiac risk factors were more abundant in affluent countries, but cardiac events and death were more common in poor countries. Dr. Yusuf even tells us why that is likely to be the case: better, more routine pharmacotherapy (the main focus of his career), and revascularization (angioplasty and coronary bypass), in the affluent countries.

The logical fallacy in Dr. Yusuf’s recent conclusions- among them, that meat is protective against heart disease and vegetables are not- is not only flagrant, but flawed at a level that would earn demerits in Epidemiology 101. I say this reluctantly, and with genuine surprise that a scholar would so misconstrue even his own work, which has shown just the opposite about both heart disease, and stroke.

Poor countries traditionally eat little meat, and have a very high intake of carbohydrate. In some cases, they have a high intake of fat, too, but from plant sources rather than animal; this is true, for instance, in rural Greece and other Mediterranean populations. In almost no instance do they have a high intake of saturated fat. We know, because it’s on prominent display, that when countries with traditionally high-plant, high-carbohydrate, low-saturated-fat and low animal food diets switch to the more “affluent” pattern of eating more meat, their rates of obesity and chronic disease rise. This is perfectly clear in both India and China. In this matter, too, Dr. Yusuf’s own prolific work inveighs against his recent ruminations.

True poverty has its own serious drawbacks, of course, from general deprivation and stress, to prevalent substance abuse, nutrient deficiencies, and poor medical care. The main reason people do or don’t develop coronary arteries plugged up with plaque happens mostly at home, and is all about lifestyle; but the main reason they do or don't have a MI or die of one happens mostly in hospitals, and is all about modern medical care. The very weak, case-control data recently tortured by Dr. Yusuf almost certainly mean that rates of death from heart disease are lower where meat intake is higher because those are the very places where more affluent populations get state-of-the-art cardiac care.

Or, if you prefer the sound bite version: eat your fatty meat, skip the vegetables, and you can stick around anyway thanks not to good health, but the technical skills of your cardiothoracic surgeon.

To see the truth about the prosecution’s case, Vinny says you must turn it around, and look at it another way; he compares the geometry of a card to a brick to make his case. If we apply that basic logic here, we might ask: well, what happens within a given population, where access to medical care is the same, when diet is changed? We have the answer. Randomized trials including the Lyon Diet Heart Study, PREDIMED, and others have shown, over a span of years and in multiple countries, that shifts to more plant foods, unsaturated oils, and less meat reduce heart disease, other chronic disease, and rates of premature death from all causes.

In My Cousin Vinny, the prosecution was not insincere- but they were most assuredly incorrect. Just like them, Dr. Yusuf may have shown views of an argument that looked convincing to the gullible, but that prove to be nothing more than a house of cards.

 

-fin

David L. Katz

Director, Yale University Prevention Research Center; Griffin Hospital

Immediate Past-President, American College of Lifestyle Medicine

Senior Medical Advisor, Verywell.com

Founder, The True Health Initiative

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