Blog | Friday, April 7, 2017

Diet and truth: tales of dogma, or data?


In late February, Dr. Salim Yusuf, a prominent cardiologist, gave a talk at the Zurich Heart House, which was circulated on YouTube before it was pulled, in which he alleged, among other things, that Ancel Keys had fudged his data. I have been corresponding since with a number of investigators who were there, who worked directly with Dr. Keys, and they are uniformly outraged. The allegation is not based on any privileged, first-hand knowledge Dr. Yusuf happens to have, but rather simply repeats another secondary source that was wrong.

These days, there seems to be a thriving cottage industry in revisionist history about the work of Dr. Keys, based on the notion that if you repeat a lie (or, to be generous, a mistake) often enough, it becomes the truth. It does not. A group of us, including those directly involved in the Seven Countries Study, are working to address that definitively with a reality check in the form of a White Paper citing primary sources and the actual data. That will take a little while, so stay tuned.

Other objectionable elements in Dr. Yusuf's talk are more readily addressable right away. Citing observational data of his own, Dr. Yusuf asserted, after noting that he has no expertise in nutrition, that in effect, everything we know about diet and cardiovascular disease is wrong. He told the world that eating fish is neutral, eating vegetables useless, and that heart disease rates go down as meat-eating goes up. If only he had recommended smoking cigarettes, the bizarre, surreality of it would have been complete enough to rival that famous scene in Woody Allen's film “Sleeper.”

Of course, this is wrong, and strangely, for a researcher who has written many times on matters of epidemiologic methodology, wrong at the level of Epi 101.

Dr. Yusuf was citing observational data across many countries. The sine qua non of interpreting such data reasonably is the avoidance of the ecological fallacy, in which A and B both happen but are “true, true, and unrelated.” For instance, there is much less Ebola where there is more 4G LTE cell phone service, and more Ebola where cell phone service is poor, patchy, or absent. This, of course, is NOT because 4G LTE cell towers protect against the Ebola virus, but because Ebola is endemic in poor, rural areas of sub-Saharan Africa that lack such towers. There are innumerable examples of similarly nonsensical associations.

In the recent talk, Dr. Yusuf explicitly noted looking across a range of countries both rich and poor. The idea was to make the findings robust across diverse populations, and that might have been a good idea had the principles taught in Epi 101 (and yes, I have both taken, and taught, Epi 101) been respected, but they were not.

Sticking with only the most obvious of rebuttals: meat is a very small part of the diets in poor countries. As countries become more affluent, they can afford, and, sadly for the health of people and planet alike, generally choose to eat more meat. But affluence doesn't just procure meat. It also procures medicine, and technology. Countries that eat more meat have more cardiologists to prescribe drugs, and perform angioplasties; they have more cardiothoracic surgeons doing coronary bypass procedures.

Dr. Yusuf did not see an inverse association between meat intake and cardiac risk factors in his data; the inverse association was between meat intake and heart attacks and death. Those are routinely prevented in affluent countries not by healthy living, alas, but by intracoronary stents and polypharmacy.

One obvious way to confirm or refute the merit of cross-sectional data is to look for change over time in those very behaviors in a given population, and then ask if the results were as predicted. Cultural transitions in both India and China have shifted traditional, plant-based diets to more meat-centric, Western type diets, and rates of chronic disease in general, diabetes and heart disease in particular, have skyrocketed. These massive examples, alarmingly on display for all the world to see, belie Dr. Yusuf's conclusions.

I was privileged to be in a group of prominent colleagues, including the immediate past president of the American College of Cardiology, who offered up just such rebuttals to Dr. Yusuf's dangerous mistake, in an article in Medpage Today. That piece, however, warrants something of a rebuttal of its own, because it contends that we nutrition experts were defending “dogma.” As someone who has ranted against the perils and demerits of dogma many times, I want to protest, and clarify.

We actually know some things, and it isn't dogma to say we do. It's not dogma to defend heliocentrism against excessive scriptural literalism; it is irrefutable fact. And though many fewer accept it as such, so is evolution by natural selection. So is climate change. Scientists throughout history have at times died defending truth objectionable in their day, and the forces that burned them at the stake were the forces of dogma. True scientists never campaign to defend dogma; they campaign to overcome it.

In nutrition, too, we truly do know some things. Before ever getting to ourselves, I presume we can agree that when zoos give meat to the lions and eucalyptus leaves to the koalas, it is not in the service of dogma. It's not in the service of data from randomized controlled trials, either, because to the best of my knowledge, zoos don't randomly assign koalas to leaves versus hunks of wildebeest before deciding what to feed them. Rather, it actually is possible to know some things based on consistent observation and sensible interpretation in context.

We know what to feed dogs and dolphins, porcupines and penguins and tropical fish accordingly. We have the same bounty of observational information about Homo sapiens.

But then we also have much more, because we do indeed have data from randomized trials, too, showing again, and again, and again much the same thing. Across populations and places around the world, decades and generations and research methods; diets rich in vegetables, fruits, whole grains, beans, lentils, nuts, and seeds and plain water for thirst lower rates of chronic disease and premature death, and diets lower in these and higher in meat, soda, and processed foods do the opposite.

The defense of this contention, which enjoys the support of a global who's who in public health, owes nothing whatsoever to dogma, but rather is richly informed by data. It is a defense against dogma, a defense of both science and sense where they converge in a veritable sea of supporting sources.

Those of us defending what we truly do know about diet and health generally need not fear being burned at the stake these days for our pains. But since diet and lifestyle are the leading determinants of years added to or taken from lives, and life added to or taken from years, there certainly are lives at stake in this debate. The lives of the public that science and medicine are intended to serve.

For that very reason, science and sense must prevail. Tales wagging dogma are the very opposite of what those devoted to nutrition in the service of public health are defending; they are the menace we are working to contain.

David L. Katz, MD, FACP, MPH, FACPM, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his blog at The Huffington Post.