Scarcely a week goes by these days without hearing yet again from some perch of lofty intellectual reflection that we know nothing about the basic feeding of Homo sapiens. We are told our research is flawed, our assessments useless, and thus our knowledge permanently something near to nil.
If true, this would be deeply disturbing. Diet has been firmly planted on the short list of leading root causes of premature death and chronic disease in the United States for the past quarter century. It has evolved to become the number one cause, and around an ever-growing swathe of the world. Imagine actually knowing nothing about the single factor that siphons away the most years from lives, the most life from years in the modern world. If true, it would seem to signal an urgent, desperate need to figure something out fast so that corrective action could be taken.
Regarding corrective action, we seem mostly disinclined- favoring the profits of the status quo over the promise of vastly better health for our children (and ourselves). Regarding the narrative of perennial befuddlement- it is entirely untrue. Truly.
We actually know more than enough about diet and health, the full range of crucial, fundamental truths- to prevent up to 80% of chronic disease and premature death in the industrialized countries around the world. We know enough to reduce personal risk by that same sum.
So how is it we can even manage to seem so utterly and perennially clueless on the topic?
Easy. The whole explanation spills out of the simplest of thought experiments. Let’s imagine we are studying exercise the way we study diet.
We must begin by looking right past the veritable mountains of evidence that routine exercise massively benefits health in almost every way imaginable. We must ignore the obvious implications of our long past, adaptation, and evolutionary biology, too. We need to ignore sense, empiricism, observation, and the patterns visible to us all throughout our lives before ever we bogged down in doubts about randomized trials. In short, we must start by overlooking the incontrovertible fact that physical activity is good for health in general, and that there are many specific variants on that fundamental theme that serve the goals of vitality and longevity.
Instead, we must study with a great pretense of seriousness the component parts of component parts. We must do so sedulously, endlessly, and emphatically. We must subordinate the role of sense to the point that any question is admissible, and the more outrageous the answer, the more headlines it must demand.
What are such sense-free questions, addressing component parts of component parts? They are virtually infinite- offering careers to large cohorts of the dubiously curious. So, for instance, some researchers might “constructively” pursue the implications of fashion.
One group would report the benefits of hiking in earth tones. Another, however, might publish on the benefits of hiking in pastels. Yet another would muddy the waters by introducing another variable, and note the advantages of indoor aerobics wearing primary colors.
Then, our problems would begin. Those favoring any given color would design trials to favor that color (designing studies to favor a desired answer is far easier than you might think). They might, for instance, recruit a group inclined to wear earth tones, then randomly assign them to hike in those favored hues, or in pastels. Those in pastels, distraught and distracted by their sartorial misfortunes, would be less happy and energetic. This group would tell us the benefits of hiking are obviated by the wearing of pastels.
The other group, of course, would do something diabolically clever, and diametrically opposed, and wind up publishing a study that explained the clear superiority of pastels. The media would treat both studies as absolute truth for their respective span of 20 seconds in the sun, largely ignoring their extreme mutual incompatibility. An anointed uber-intellectual would eventually publish a commentary in a prestigious journal, far more widely read than either study, and spawning a third set of headlines, telling us that such conflicts of hue obviate all knowledge of any alleged health benefits of exercise.
And we, in our gullible, complicit, colluding multitudes- would head back to the couch, remote in hand, with a smug “I knew it all along” look on our faces.
But this, of course, is just the first sedentary toe in the vast waters of our burgeoning exercise confusion. We could study every version of every kind of footwear, underwear, hats and gloves. We could study temperature, time of day, dew point. We could study latitude, longitude, spirituality, and choice of toothpaste.
We could also study surrogate markers designed to obscure rather than advance understanding. For instance, running and hiking are good for health, and running and hiking can produce blisters and callouses on the feet. So, studies could be designed that ignore long-term effects on fitness and health, just focus on podiatric callouses, and then extrapolate blithely. An Emory board to the foot once daily produces a callous roughly comparable to hiking 5 miles a day; therefore, Emory board use should be considered an alternative means to the health benefits of bountiful walking.
We might also work endlessly to refine our knowledge of the active ingredient. However much it might appear that walking, hiking, running, jogging, biking, swimming and such improved fitness and health relative to couch surfing, we could renounce that high-level association as too vague. We could tell one another, in The New England Journal of Medicine and The New York Times, that we don’t actually know this until we know which part of it is the answer.
And so here we might study steps, strides, and strokes. Which step, on a run of say 5 miles, confers the alleged health benefit? Until or unless we can say, we must say we are clueless. When studies of step 2637, isolated from all others, show no decisive contribution to health, we should express with alarm that since a given step in a walk, jog, hike, run does NOT confer a health benefit, then perhaps no step confers a health benefit- and therefore, ipso facto, walking, hiking, jogging, running CANNOT confer a health benefit after all. We might do the same for strokes in the water, and turns of the bike wheel.
Affronted by this, exercise researchers might then devote years, and millions in research funding, to re-proving what we had long known. In fact, entire careers could run on reaffirming the obvious (as we keep doing in nutrition). Other careers could thrive entirely by refuting it again. We could run exercise research in such permanent circles that we only ever conclude nothing about the health benefits of actual running, entirely obvious at the start.
There are, of course, relevant details about exercise we don’t know that can and should inform the research we do. But this pursuit of what we don’t yet know does nothing to annul what we do. Routine exercise is profoundly good for health, and there are many valid variants on that basic theme.
Just the same is true of diet.
At some level, you know this already. Do you genuinely get hung up on the relative nutritional merits of jelly beans versus garbanzo beans? Walnuts versus doughnuts? Actual fruit, versus Froot Loops? If not, then you seem to know some of the fundamentals of eating well we devote part of every news cycle to denying.
The contention that we are clueless about diet and health, that all measures are bereft, all knowledge suspect, all research questions however seemingly inane admissible- is the rubbish it seems. It is a pop culture myth. The notion that we can only know with data from a RCT is as well; just ask yourself if you really need to find a meta-analysis to know whether to use water or gasoline to put out your next campfire.
The entire nutrition narrative has been hijacked so that:
A) Silly (I’m being kind) questions are posed and tested
B) Uninformative, conflicting, confusing, contrarian answers ensue
C) Great academics and intellectuals, generally of the sort that opines from some lofty sacred perch but who doesn’t actually DO nutrition research, or clinical care, or much of anything of practical value to the world- swoop in to tell us how hopelessly shabby the field and overall state of our understanding are
D) The media propagate all of the above
E) Massive pseudo-confusion prevails
That leaves just one important question as yet unanswered: why?
That answer is obvious. Profit. There is a whole lot of profit to go around in perpetual, utter befuddlement about diet. Big Food gets all the cover they need to put new shades of lipstick on a whole parade of pigs, and peddle them to us. Big Pharma gets to keep treating diseases we never needed to get in the first place. Big Weight Loss can keep charging people to fix a problem our culture caused on purpose. Big Media get to afflict the nutritionally comfortable, and comfort the nutritionally afflicted, ad nauseum. Big Publishing gets to publish the next installment in the endless cycle of “I’m right, everyone else is wrong” quick-fix magic. And careers in Big Science can flourish refuting and reproving the established and obvious, rather than doing something of actual use. All this despite the fact that mountains of evidence, the meanest application of sense, the common experience, all overlaid by the consensus perspective and personal practices of the world’s leading experts all point to the same fundamental truths about diet and health.
A long list of entities profit by denying this. But there’s no denying the obvious: that list probably does not include you.
David L. Katz, MD, MPH, FACPM, FACP, FACLM, is the Founding Director (1998) of Yale University’s Yale-Griffin Prevention Research Center, and former President of the American College of Lifestyle Medicine. He 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. He has made important contributions in the areas of lifestyle interventions for health promotion; nutrient profiling; behavior modification; holistic care; and evidence-based medicine. David 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.