What’s Healthy and What’s Not?

As many fellow health buffs will no doubt attest to, it is often very difficult to get a consistent idea of what is healthy and what isn’t. Not only do laymen often disagree vehemently with one another — everyone has their own anecdote or folk remedy to swear by, science be damned — but it seems that not a month goes by without some study finding contradictory evidence about the healthiness of a particular food or beverage, often turning back years or even decades of nutrition science (e.g., the recent revelation that fat may not be so bad after all, that eggs and coffee are good for you, and that salt and sugar are far worse than previously believed).

The New York Times drives home this point with an article about a study that polled both nutritionists and a sample of the American public to compare their thoughts regarding some common nutrition battlegrounds. Unsurprisingly, the results showed a big gap between experts and everyone else, as well as revealing divisive views within each community, too. 

Here is a colorful breakdown of the results:

Nutritionist IVNutritionist IIINutritionist II

So we see quite a mixed bag of results: foods that both sides agree are healthy or unhealthy, and foods that both sides are either deeply divided on or uncertain about themselves. All this goes to show that while there are some clear ideas of what constitutes a healthy diet — most fruits and vegetables, most whole grains, lean meats — there are plenty of things that are still being worked out. I personally think it reflects just how new nutrition science is as an organized field of study (although observations regarding health and diet have been around for thousands of years, only since the 20th century did something akin to nutrition science emerge).

A couple of years ago, the Times had another piece that was exploring why nutrition research seems so inadequate. Much of it just comes down the complexity of both the human body and our ability to accurately observe it.

The 600,000 articles — along with several tens of thousands of diet books — are the noise generated by a dysfunctional research establishment. Because the nutrition research community has failed to establish reliable, unambiguous knowledge about the environmental triggers of obesity and diabetes, it has opened the door to a diversity of opinions on the subject, of hypotheses about cause, cure and prevention, many of which cannot be refuted by the existing evidence. Everyone has a theory. The evidence doesn’t exist to say unequivocally who’s wrong.

The situation is understandable; it’s a learning experience in the limits of science. The protocol of science is the process of hypothesis and test. This three-word phrase, though, does not do it justice. The philosopher Karl Popper did when he described “the method of science as the method of bold conjectures and ingenious and severe attempts to refute them.”

In nutrition, the hypotheses are speculations about what foods or dietary patterns help or hinder our pursuit of a long and healthy life. The ingenious and severe attempts to refute the hypotheses are the experimental tests — the clinical trials and, to be specific, randomized controlled trials. Because the hypotheses are ultimately about what happens to us over decades, meaningful trials are prohibitively expensive and exceedingly difficult.  It means convincing thousands of people to change what they eat for years to decades. Eventually enough heart attacks, cancers and deaths have to happen among the subjects so it can be established whether the dietary intervention was beneficial or detrimental.

Indeed, it is difficult to pinpoint what aspects of a person’s diet, if any, contributes to their health and wellness (or lack thereof). You can make the general observation that a group of people who eat a certain thing live comparatively longer, healthier lives, but finding a clear causal relation between the two factors is next to impossible. There are many correlations and associations, but little strong causation. Therein lies the crux of the matter: nutritionists must concede that there is still a lot we do not know, and emphasize the limits of any findings we do come across.

One lesson of science, though, is that if the best you can do isn’t good enough to establish reliable knowledge, first acknowledge it — relentless honesty about what can and cannot be extrapolated from data is another core principle of science — and then do more, or do something else. As it is, we have a field of sort-of-science in which hypotheses are treated as facts because they’re too hard or expensive to test, and there are so many hypotheses that what journalists like to call “leading authorities” disagree with one another daily.

It’s an unacceptable situation. Obesity and diabetes are epidemic, and yet the only relevant fact on which relatively unambiguous data exist to support a consensus is that most of us are surely eating too much of something. (My vote is sugars and refined grains; we all have our biases.) Making meaningful inroads against obesity and diabetes on a population level requires that we know how to treat and prevent it on an individual level. We’re going to have to stop believing we know the answer, and challenge ourselves to come up with trials that do a better job of testing our beliefs.

Again, none of this means that we need to be totally agnostic about certain questions regarding health; as the above data show, there are plenty of areas in which the evidence is clear (unless both nutritionists and society at large are wrong, which I suppose cannot be totally ruled out). I do think a certain degree of self experimentation is required as well. No one should treat themselves like a lab rat, but given the variability of each human body, it is important to pay attention to what seems to work for you and compare that to the standard science.

In any case, the fact is, for all the mounting health problems like obesity and diabetes, humans are on the whole much longer lived, much healthier, and much less prone to a host of once common diseases and conditions than ever before. It is unlikely that we will ever decline to pre-industrial levels of health; even in the developing world, malnutrition and its related health problems are largely in the declining, although that has as much to do with access to vaccines, clean drinking water, and medicine as anything else.

For all the uncertainties and frustrations we face in trying to eat and live optimally, we have still come a long way from our ancestors. Perhaps we should reflect on that next time we find ourselves struggling to choose between sushi and burgers.

What are your thoughts?


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