Diet: How Can We Seem So Clueless?

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For those in haste, I will put the bottom line here at the top: we are not, in my opinion, even remotely clueless about the (basic care and) feeding of Homo sapiens. We know full well what the evidence-based, consensus-based fundamentals of a health-promoting dietary pattern are.  Indeed, we know enough about those basic truths to apply them, in the context of several other basic truths about healthy living, to prevent some 80% of all major chronic disease in the world today, and to slash our personal, lifetime risk by as much.

  We know enough to add years to life, and life to years. 

We are not clueless, and it would be utterly bizarre if we were.  After all, we know what to feed cats and dogs; chickens and horses; tropical fish and African rock lizards; lions, and tigers, and bears.  Oh, my, how odd it would be if we knew what to feed every species on the planet but our own! It’s not so.

But as I write this, an intense argument is playing out over the report of the 2015 Dietary Guidelines Advisory Committee, the scientific report that underlies the updated Dietary Guidelines for Americans.  My position on the DGAC report is a matter of record. We have recent word that the alleged controversy is fueled by, what a surprise, money, and motivated by profit. We also have early indications that irreparable damage has already been done. The less the support and respect for the work of actual nutrition scientists, the more readily the lobbyists and politicians make mincemeat out of the report, and replace evidence-based dietary guidance with self-interest.

That process is now on-going, and looking on is more nauseating than watching the proverbial sausages being made.

Here and now, however, I leave all that aside to offer what I hope will be a few more generalizable considerations about research, and its translation into understanding. Given the tomes of research related to diet and human health, how is it possible for us even to seem clueless?

Given the volume of study to date, how can fundamentals appear controversial at all? And, importantly, given these counter-intuitive dilemmas: what is the remedy?

There are, of course, other good sources on this topic, some quite new. My intent, therefore, is not to be comprehensive- but memorable. I will attempt to distill the cause of, and cure for, pseudo-confusion about diet into the handling of four easily remembered questions that relate to the processes of science in general. 

1) What paddle?

Science is incremental. Each new thing we learn is added to what we knew before, and understood only in context. New information may reaffirm what we thought we knew; challenge it; or modify it.  But it virtually never replaces it. Thus, if we think of the scientific process as a paddle, it is a canoe paddle, not a Ping Pong paddle!  In Ping Pong, the action goes this way, then that, in a constant, dizzying state of reversal. Those who profit from dietary confusion- and alas, that’s a sizable group of industries- may prefer that we treat science like Ping Pong, our attention forever diverted by a sequence of conflicting, hyperbolic headlines.

  Science is like a canoe paddle, however, forever dipping into the same basic waters of truth, and applied to move us toward the source of deep understanding. Progress is incremental, and additive. Sometimes we go backward, sometimes sideways. Sometimes the waters are placid, sometimes churning. But those are details. The process is what matters. Slow, steady, progress, with each new advance toward the destination, each stroke of the paddle, contingent on all that have come before- not an alternative to them.

So, the answer: canoe, not Ping Pong!

2) Compared to what?

The current DGAC report advises us to stop worrying about our intake of dietary cholesterol, and I agree. However, I have heard from colleagues, notably vegan colleagues, who disagree. This would seem to suggest confusion and discord, but that’s not really the case. The DGAC is providing population-level guidelines. The starting point for the changes in diet that would advance public health is the diet that currently prevails, the so-called “typical American diet.” The DGAC is in accord with the evidence, as best I can tell, to say that dietary cholesterol does not play a significant role in elevating blood cholesterol levels, or cardiovascular risk, in the current dietary context. I believe my vegan colleagues are also correct that against the backdrop of an optimal, plant-based dietary pattern, the addition of dietary cholesterol is apt to have much more discernible effects. We are therefore not confused, and there is not even any real disagreement. Rather, the effects of dietary cholesterol on health are, unsurprisingly, related to the pattern and quality of the baseline diet.

So, the answer: the baseline matters!

3) Instead of what?

The now notorious meta-analysis so often invoked to tell us that saturated fat is “good” for us now showed no such thing. It actually showed that across a narrow range of saturated fat intake, there was no meaningful change in rates of heart disease; they were high at both ends of a small spectrum. But leaving that aside, there is an obvious question we should be inclined to ask whenever we hear about what a food or nutrient will do for health: instead of what? Beans, for instance, are terrific for us- but we could demonstrate an absence of clear benefit if we compared them to lentils, which are equally terrific. Trans fat is terrible for us, but we could make it look good if we compared it to…botulinum toxin. The example is willfully silly, but makes the point just the same.

A newer study out of Harvard addressed the “instead of what?” question for saturated fat, and produced very predictable results, in accord with prior science and intuition alike. When saturated fat calories were replaced by added sugars and refined starches, health outcomes were comparably bad both times.  When replaced by whole grains, or unsaturated oils (from nuts, seeds, olives, avocado, and to a lesser extent, fish)- health outcomes improved markedly.

Thus, the same body of evidence could be used to argue that saturated fat is “good” now, or that it’s every bit as bad as sugar. This looks a lot like confusion, but it’s about a rather common sense question: instead of what?  When “this” replaces “that” the effects are dependent on both.

So, the answer:  this AND that both matter!

4) What prize?

Finally, if we are told that some food or nutrient is the means to an end, we need to know: what end?  Returning to that infamous meta-analysis about dietary fats, headlines misleadingly suggested that “butter was back.”  To what end?  As noted above, the study actually showed that health outcomes were, essentially, THE SAME, at the narrowly differentiated high and low end of the spectrum for saturated fat intake.  So, simply confronting this study with a question about the prize would have clarified: there is no prize. Eat more saturated fat, or less, and your health is apt to stay about the same.  Contrast this with the prize associated with a genuinely optimal dietary pattern, as practiced in the world’s Blue Zones: vitality and longevity; more years in life, and more life in years; virtual immunity to the scourges of modern epidemiology: heart disease, cancer, diabetes, stroke, dementia, and more.  Now we’re talking!  A longer, better life is a helluva prize.

Two different ways to get the same bad outcome don’t serve up much of a prize. The opportunity to live long and prosper from vitality all those years is, conversely, as good as it gets.  Don’t forget to ask what ends attach to the means being promoted.

So, the answer: it’s all just noise if there is no prize!

We are not clueless about the basic care and feeding of Homo sapiens. The fundamentals of healthful eating are evidence-based, consensus-based, science-based, and sense-based. They are good for the people, and good for the planet. The pseudo-confusion and feigned controversy now propagating is much about profit, not at all about public health. It derives from a clear and omnipresent peril in the interpretation of research: an answer is never better than the question. At the bedrock of understanding, one finds good questions.

Ask the right questions, and the answers start to make a whole lot more sense.

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