The Many Flavors of Optimal Nutrition

Some years ago, I wrote a commissioned article for a peer-reviewed compendium, entitled “Can We Say What Diet is Best for Health?” 

My answer at the time was, in equally emphatic parts, yes, and no.  Those conclusions remain, in my opinion, fully current today.

No, we cannot declare that any one, specific, prescriptive dietary pattern is definitively best for the health of all people.  But yes, we know with great confidence the general theme of healthful eating for all Homo sapiens, just as we tend to know with great confidence the general dietary requirements of species other than our own.  We, too, are a kind of animal, and we, too, have dietary adaptations and requirements that hide in plain sight.

More recently, but still some years ago, I wrote a column entitled “Toward a One Diet World.”  Here, I noted that many of the debates (and pseudo-debates) about diet and health failed to consider sustainability and environmental impact and were thus, in a word, obsolete.

Before we exhausted soil and aquifers; before we began razing rainforest to pasture cattle; before we massively overfished our overheated oceans; before 8 billion hungry Homo sapiens were clamoring for sustenance every day- we had more dietary options.  We were always bounded by the requirements of our own health, but a planet of seemingly inexhaustible resources permitted us to indulge.  The precarious state of planetary health induced by those indulgences has changed the equation.  Now, the only diet that may reasonably be considered “healthy” for people is one that is so for the planet, too.  We have some hope of being healthy, vital people on a healthy, vital planet- or we have no hope of being healthy, vital people.  Thus, the plight of the planet- of our own devising- constrains the options of genuinely healthful eating ever more stringently.  I concluded then, and maintain now, that this funneling culminates in very limited dietary choice on an ever more narrowly bounded theme.

Fortunately - and it is indeed fortuitous, for it need not have been so - the clear fundamentals of diet for our own health, and those for sustainability, for the safeguarding of aquifers and climate, imperiled ecosystems and biodiversity- are all but perfectly confluent.  Thus, the dual imperatives of human health, and planetary health, cry out in a shared voice the importance of honoring the same, basic dietary theme.

But while basic conclusions about the theme of optimal eating are the same over time; while the messages in defense of our own health and that of the planet are much the same - people are different. Our biology is shared, but our heritage, culture, upbringing, perspectives, and preferences diverge.  We are all bounded by the same ineluctable facts, yet each entitled to our own tastes.  Can optimal nutrition- the best diet for health- accommodate this dichotomy?

Yes.  Emphatically: yes!

The neglect of cultural diversity in the generation of dietary guidance long flew largely under the radar. In recent years, however, this deficiency has at last been appropriately called out.  The blinkered view that passed for the state of the field- the notion that one dietary pattern fits all- is no longer acceptable.  There were, of course, entities with a grander vision all along, rightly linking health with heritage, and generating invaluable resources in accordance with that fusion.  Others are now joining in the generation of materials to address the means to eating well across a multicultural expanse.

In my own work, thanks to the knowledge and skill, diligence and craft of my dietitian colleagues, we are able to stratify a wide array of dietary patterns into the same ten tiers of objectively measured quality.  In other words, we can reach the same threshold of “optimal nutrition” (the top decile of the Healthy Eating Index 2020) with a great variety of food assemblies, responsive to culture, upbringing, preferences, sensitivities, and personal dietary ideology.

There is no reason, for instance, why a Chinese, or Vietnamese, or Japanese - American whose native diet never included dairy, should have to eat dairy to manage high blood pressure (e.g., the DASH diet).  There is no reason why a vegan or Paleo adherent should have to eat dairy, either.  There is no reason why a vegetarian should have to eat fish.  A low-carb proponent need not eat grains.  Within the bounds of aggregated evidence, optimal nutrition readily allows for all such, and innumerable more, variations on a common theme.

A Mexican-American could readily manage hypertension with a diet meeting all the same nutrition standards as DASH, but with a dash (or more) of jalapeno in the mix.  A South Asian (Indian)-American could do the same, but with a splash or more of curry. Real food, not too much, mostly plants- diets made up mostly or wholly of vegetables, fruits, beans, lentils, whole grains, nuts and seeds, and water for thirst- come in many flavors.

What evidence says so?  Too much to summarize in fewer than hundreds of pages.

Some years back, I took part in a debate about the evidence, or lack, supporting plant-predominant diets.  My “opponent,” not formally trained in research methods, advised the audience that randomized controlled trials were the one, “true” form of evidence- and that I would be talking to them only about the “lesser,” observational evidence of the Blue Zones.

My opponent was wrong- in both practice, and principle.  I cited roughly two dozen randomized controlled trials first, illustrating the bounty of evidence underlying the basic theme of healthful, sustainable eating.  But I am formally trained in clinical research methodology - and accordingly, I know the limitations as well as strengths of any given study design.   It is because I have conducted and published RCTs; conducted and published systematic reviews and meta-analyses  - that I consider the Blue Zones the best of evidence.

The aim of any clinical study is to approximate what is true for people not subject to the tight constraints of a randomized clinical trial, but living in the real world.  The Blue Zones offers up such evidence directly- showing us all, across five (thus far) distinct cultures and four continents- how variations on the theme of optimal diet (and lifestyle) can serve up the same great outcomes: a bounty of years in life (longevity), and a bounty of life in years (vitality).

As we think about optimizing nutrition for all, and honoring our diversity, a great analogy from biology suggests itself.  Antibodies are complex protein molecules that must be able to bind with antigens to enable the robust defenses of our immune system.  The trouble is that antigens- foreign materials representing a potential threat, borne, for example, by bacteria, viruses, parasites, or toxins- come in near infinite, if not actually infinite variety.  The immune system addresses this challenge in the most elegant manner: it builds proteins with both “fixed” and “hypervariable” regions.  The fixed region is constant, and houses all of the core mechanics an antibody requires.  The hypervariable region is the clasp, and is designed to correspond with any given antigen.  The same, fundamental functions can thus be targeted to an infinite variety of provocations.

In much that way, we can fix the fundamentals of optimal nutrition for people and planet alike- and allow for hyper-variation of herbs and spices; sauces and seasonings; flavors and preparations.  We can eat for the love of health, and love the food, too. The work I am doing now delivers on that very promise.

While trusting entirely in that value proposition, I would very much like to see it formally validated- so a quick shout-out to any of my nutrition research colleagues who happen to be reading this.  While Food-as-Medicine, and Lifestyle-as-Medicine interventions have considerable support in the scientific literature, extending to economic benefit- there are too many studies in these domains with underwhelming results.  The primary explanation for most of these is “too little, too late” or what I have called “the parable of the tiny parachute.”  A study of parachutes the size of postage stamps might conclude that parachutes don’t work, but it would be wrong.  Adequate parachutes work beautifully; inadequate parachutes are…inadequate.  The same is true, of course, for Food-as-Medicine.

To achieve an “adequate” dietary effect requires that study participants actually eat the assigned food, and therein lies a second problem.  Historically, dietary intervention studies have been of a “one size fits all” approach; everyone in the intervention group receives the same diet.  But with new means now at our disposal, we could instead assign a fixed diet quality, and associated ranges/doses for select foods and nutrients, while allowing the dietary pattern or style to vary, in accommodation of diverse palates and preferences.  Dietary interventions could resemble antibodies- built to be fixed and constant in the key, functional components (to which the “intervention effects” could be attributed), yet highly adaptive in other ways.  I anticipate unprecedented adherence, satisfaction, and outcomes when dietary intervention studies begin to honor the crucial consideration of personal choice.  So, calling all colleagues: if this is of interest, let’s talk!

For everyone else, time to conclude.  If there really were just one “best diet”- as every fad diet author of the past half century has maintained- and if it didn’t happen to be a diet we were willing to eat, or perhaps not even a diet we were biologically capable of eating (e.g., a dairy-containing diet for a lactose intolerant population) - then we would be flat out of luck.  Fortunately, the fad diet formula, however effective at selling books, is a load of reheated hooey, served up again and again.  The best diet for health can readily satisfy a diversity of palates; and that most noxious of food additives, dogma, appears nowhere on the menu.

Diet quality is the single leading predictor of mortality and disease risk in the modern world.  Food-as-Medicine, accordingly, has tremendous potential to add years to lives, add life to years, and save money doing it.  That potential will be best fulfilled by those who respect that the fundamentals of optimal nutrition come in many flavors.

-fin

David L. Katz, MD, MPH is a specialist in Preventive Medicine and Public Health.  He is the founder of Diet ID, Inc, Chief Medical Officer for Tangelo, and past president of the American College of Lifestyle Medicine.