I am going to go out on a limb- as in the photo- and contend that pretty much everything we’ve heard about “personalized nutrition” is just the kind of tree that makes it hard to see the forest.

Writing on the topic of sorting out one’s nutrition the day after Thanksgiving is perhaps a dubious proposition. But then again, when better to reflect on the customized routes to optimal eating than right after a culture-wide exercise in communal debauchery? On this, the morning after, I confess to writing in loose-fitting sweat pants!

Anyway, back to that forest through the trees.

Imagine you had a family history of, say, stroke- and accordingly you wanted to optimize the management of your blood pressure, the most important risk factor. This being the age of personalized everything, and you being uniquely you- we may presume you would not want generic blood pressure management. You would want personalized blood pressure management, just right for you. Customized, and precise.

Given that, what’s the first bit of actionable information you would seek? Would it be the distribution of bacterial colonies in your gastrointestinal tract? Would it be some assembly of single nucleotide polymorphisms (SNPs)? Something to do with your epigenetic settings? Circulating cytokines, enzymatic activity, or some especially esoteric measure of biochemical balance?

Or, would it be- and, as noted, I am going out on a limb- your blood pressure?

There is an expression from the business world that pertains as readily to medicine: we generally only manage what we measure. We may inform our understanding of why blood pressure is what it is, and the best ways to optimize it, with an array of ancillary measures- those above, and others. But the whole enterprise begins by measuring blood pressure itself.

This is the general rule of measurement and management: if we tend only to manage what we measure, we need to measure what matters. To manage blood pressure, we start by measuring it.

That’s necessary, but not sufficient. There is little point in knowing what the measure of something is, absent a clear idea of what its measure ought to be. Measures in medicine- blood pressure, heart rate, temperature, LDL, blood glucose, CRP, etc.- are always in comparison to a reference standard deemed “normal.” The concept of normal in such use is not a subjective judgment, but an objective range of values associated with the best health outcomes in individuals and populations. The “ideal” blood pressure is not contrived; it’s in a range that amply perfuses all vital organs without any excessive force damaging heart and blood vessels. Ideal is as ideal does. What ideal values in medicine “do” is contribute maximally to years in life, and life in years.

Nutrition is no different. If we want to optimize our own dietary intake, the first and most crucial information required is: what is our dietary intake now?  That general measure must in turn be operationally defined, just as “blood pressure” translates into specific components, namely diastolic pressure, systolic pressure, and the at times appended mean arterial pressure. For diet, the key components are ostensibly dietary pattern and type, intake levels of various foods and food groups, nutrient intake levels, and overall diet quality measured objectively. 

That final entry- an objective measure of diet quality- leads full circle back to the health outcomes that matter most, since diet quality is as diet quality does. Measures of diet quality- such as the Healthy Eating Index- are validated directly against the overall risk of premature death from any cause and the rates of all major chronic diseases in large populations. Dietary patterns subtending the best in both longevity and vitality are deemed best- not because of any ideology, but based on the dispassionate adjudication of epidemiology.

The personalization of diet for optimal health outcomes has suffered historically from three key liabilities. First, we have failed to measure diet routinely because the tools for doing so have been some combination of onerous and unreliable- tedious, time-consuming, expensive, and memory dependent. I am proud to report that the venture to which this phase of my career is devoted, Diet ID, has solved that problem. My team has developed an entirely new way to assess diet easily and comprehensively in mere seconds. Diet ID is to diet what the blood pressure cuff is to blood pressure. 

Second, we have tended to put the personalized diet cart out ahead of the horse. For all measures that matter, there is a range that is reasonable for us all, as a common species, prerequisite to any specific, personalized ideal. For some people, the ideal blood pressure might be 90mm Hg over 60mm Hg; for others, 120 over 80. But the ideal blood pressure for a human- any human- is never 50 over 20, or 250 over 200. The customized ideal falls- always- within the range of the communal ideal. So, too, for body mass index, heart rate, respiratory rate, and every relevant measure in biology. 

So, too, for diet. The personal dietary optimum falls within the range of optimum for our species in general. This is perfectly obvious to us when we think of any kind of animal- horses, dolphins, lions, koalas- other than ourselves. We are a kind of animal, too. The prevailing dialogue on precision nutrition tends to ignore the fundamentals that would make diet better for any human as the common bedrock on which to build up any personalized variant.

Third, we have been seduced by the new and shiny- nutrigenomics, for instance - into overlooking the tried and true. Nutrigenomics is not yet ready for prime time. Even when multi-omic platforms are, however, they are still secondary information sources. No matter what else we might measure to gauge the ideal blood pressure for an individual, we start by measuring blood pressure and knowing the range of reasonable target values.

All the same is true of diet. As the single most important predictor of health outcomes in modern countries, diet deserves to be a vital sign. At Diet ID, we are committed to making it so. Stop by to learn more. Just like the forest, we are easy to find- unless a whole lot of trees get in the way.

Dr. David L. Katz; Founder & President, True Health Initiative; founder/CEO, Diet ID; 2019 James Beard Foundation Award nominee in health journalism.