Dietary Doubts

 In Preventive Medicine Column


Diets, Doubts, and Doughnuts

In the New York Times this past week, Gina Kolata made the case that almost all studies about diet, exercise, and health are suspect in one way or another, warranting a raised eyebrow, and that therefore we are justifiably confused about lifestyle practices for health. The first point is valid; the second is utter nonsense. Let’s take them in turn.

The contention that all research addressing lifestyle practices for health is limited in some way is certainly true, to the point of being both trivial and trite. All research is limited in some way; the perfect study has never been conceived, let alone executed. But we have nonetheless used research to produce very tangible results that prove the utility of our imperfect methods. We have put footprints on the moon; eradicated smallpox; put a spaceship in orbit around Jupiter; and routinely shoot perfectly clear messages to one another by jiggling electrons in cyberspace. Anyone exploiting the tools of modern living is a living illustration that research, though ineluctably flawed, works pretty darn well.

There is, moreover, a case to make that research addressing lifestyle practices may be especially prone to important limitations. If we consider that the pinnacle of evidence in human research is, generally, the randomized, double-blind, placebo-controlled trial, the challenges are immediately clear. How do you pair exercise, or an optimal diet, with some “placebo control,” while keeping your study participants blind to their treatment assignment? How can we have some people exercise, and others not, without them picking up on it? We cannot. And that’s just the start of our tribulations with such trials.

But that does not leave us clueless, any more than the lack of a randomized comparison of treatment versus benign neglect is required to know that bullet holes through peoples’ chests warrant emergency surgery. We have no randomized trials telling us that water puts out most fires, and yet our firefighters carry on as if they know what they are doing. We had no perfectly unassailable proof that we could put a spaceship into orbit around Jupiter, until we went ahead and based on imperfect science, did exactly that.

What we have done in all areas where science has proven its inimitable utility is look at the weight of evidence, and apply sense. That formula is vastly more powerful, useful, and nearly perfect than any one study has ever been.

In the case of lifestyle for health, the formula works perfectly well despite the research imperfections that trouble Ms. Kolata. She is quite right to recommend a raised eyebrow about any one study, and in particular, the hyperbolic headlines it is likely to engender. But look instead at the weight of evidence, encompassing randomized trials, mechanistic studies, observational epidemiology, and real-world experience at the level of whole populations- and you generate a rather emphatic mandate to keep that restless eyebrow at its low-altitude ease.

Consider the implications for yourself, and for that matter Ms. Kolata, if the lack of “perfect” research really made us clueless about diet. We would have no idea whether lentils or lollipops were a better source of sustenance. We could not judge the differential merits of dates, and jelly doughnuts. We would not know whether oatmeal and walnuts, or Doritos and Coca Cola made a better breakfast.

I very much doubt that Ms. Kolata has any difficulty judging the relative merits of kale and cheese doodles. But once we are in for that penny, we are in for a pound. If we know, despite our research imperfections, that broccoli is generally a terrific choice, and baloney not so much, then we clearly have a basis to understand something in spite of it all. There is no reason for that understanding to end with baloney, and indeed it does not. We, and Ms. Kolata, all make confident choices every day, informed by science, guided by sense.

No single study, about diet or anything else, is perfect. If that gets you exercised, go ahead and exercise your derisive eyebrow as Ms. Kolata advises. But on the other hand, the massive weight of evidence in the aggregate tips clearly and decisively. A global consensus of expert judgment concurs. Sense, applied a bit too seldom to be called “common,” alas, aligns. Routine physical activity and a diet of mostly minimally processed vegetables, fruits, whole grains, beans, lentils, nuts, seeds and water when thirsty redounds consistently to the advantage of human health. It offers benefits to the planet as well.

I recommend that you leave your eyebrow just where it is, and lift instead your feet, and your fork, accordingly.

-fin Dr. David L. Katz;; author, Disease Proof; founder, True Health Initiative

Dr. David L. Katz
DAVID L. KATZ MD, MPH, FACPM, FACP, FACLM, is the founding director (1998) of Yale University's Yale-Griffin Prevention Research Center, and current President of the American College of Lifestyle Medicine. He earned his BA degree from Dartmouth College (1984); his MD from the Albert Einstein College of Medicine (1988); and his MPH from the Yale University School of Public Health (1993). He completed sequential residency training in Internal Medicine, and Preventive Medicine/Public Health. He is a two-time diplomate of the American Board of Internal Medicine, and a board-certified specialist in Preventive Medicine/Public Health. He has received two Honorary Doctorates. Dr. Katz has published roughly 200 scientific articles and textbook chapters, and 15 books to date, including multiple editions of leading textbooks in both Preventive Medicine, and nutrition. Recognized globally for expertise in nutrition, weight management and the prevention of chronic disease, he has a social media following of well over half a million. In 2015, Dr. Katz established the True Health Initiative to help convert what we know about lifestyle as medicine into what we do about it, in the service of adding years to lives and life to years around the globe.
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