Why Nutrition Can’t Be Completely Evidence Based and What to Do About It?

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Every single diet out there, every single approach to eating contains elements of philosophy, preconceptions, common sense or lack thereof, and beliefs. My own approach is no exception. It tries to get infomred by science as much as possible, but, as of today, it is simply impossible to have a completely scientifically based diet. And here is why:

  • there are thousands of different types of food out there and there haven’t been studies done testing each of them and their health effects
  • even if there were much less different types of food, their possible combinations and ratios would still be infinite, and it is impossible to scientifically test every single one of these combinations and ratios and how they affect health. There will always be some guy who will choose one particular combination, and base his approach around it, claiming that this approach is superior to all others – which is of course impossible to prove, and even if it was possible, the next day could arrive another guy, with even better combination.
  • Everyone needs to eat, even animals, which they do quite well, even without any science to teach them what to eat or how. Only relatively well-off people, whose most basic needs are met, can afford to spend time doing nutrition science (or any other science for that matter). But while in other sciences, we can sit and wait for the results, here we can’t: we must eat in order to survive, and we must eat even before the science tells us what to eat. Therefore we all, both on societal level, and on individual level have formed certain eating habits, and beliefs about food… well before we learned about any results from food science.
  • Therefore, once nutrition was born as a scientific discipline, it had to take into consideration what was already there, before she was born. What she found was a diverse set of ways of eating around the world, diverse eating habits, diverse cultural norms and customs around eating, etc. As modern nutrition was born in Western civilization, the first diets it scrutinized were various traditional and modern eating habits and beliefs about food found in western countries.
  • So it assumed that what most people do makes sense, and that it is normal – this was the starting point, the default diet that we all do, until we wait for the results of scientific studies. This actually does make sense: it was the best guess one could make at that time – if you see a way of eating that survived the test of the time, and is widely accepted among the population, your best guess is that such way of eating is fine.
  • At least that was the case until we saw epidemic of lifestyle diseases, such as obesity, diabetes, high blood pressure, metabolic syndrom, etc… When such diseases became so prevalent in population it became clear that something about the common way people eat is not right.
  • But then: we know something is not right, but we still don’t have all the scientific results about all the thousands types of foods and their effects… so what should we do? I think the answer is more than obvious, but I’ll write it anyway: of course we should look at our own traditional diets as they were before the onset of epidemic of such lifestyle diseases. This is our best guess right now – as this was the diet that stood the test of time, the diet that was widely employed by most of the population, and yet it didn’t cause all the diseases that our current diets cause. By “traditional diets” I’m not considering paleo or anything like that based on our modern speculations about what prehistoric people ate… which we can’t know with any certainty. I am considering ways of eating as they were the norm just around 100 years ago.
  • Of course, just because they were widely accepted by most of the population and generally didn’t make people sick, does not mean they were perfectbut they are our best guess until we get the results from science. This is a completely valid starting point, and this is, IMO, common sense.

So my starting nutritional recommendation, before science, and while we wait for all the scientific results and refinements – is: Base your eating habits around any of the numerous traditional ways of eating as they existed just before the onset of the epidemic of lifestyle diseases.

We can explain and refine it further:

I’m saying JUST BEFORE the onset of epidemic of lifestyle diseases, because these diets are most recent, we know most about them… they were here just 100 years ago and they are well documented. The further we go into the past the less we know about how people ate at those times. But we know very well how people ate 100 years ago, so it’s much easier to copy and re-do this, rather than to get more adventurous and go further in history, or like some do, in prehistory. IMO, there’s no need to go that far, because just around 100 or so years ago – we didn’t have such epidemic of lifestyle diseases that we are experiencing today.

I would also add: you can take any traditional way of eating as a good choice, but especially good choice for you would be one of these two:

  • traditional ways of eating from any region of the world that is well known for good health or longevity: this includes Mediterranean countries, East Asian countries and Nordic countries.
  • traditional ways of eating from your own country or your own culture – as this is something that probably resonates best with you in particular.

So, to sum up… how we should eat while we are waiting for what science has to say on countless nutritional open questions? My answer is:

We should eat just the way we ate before the epidemic of lifestyle diseases.

This is, IMO, common sesne, and wise approach. Of course, this is just a starting point, and as soon as we get certain results from science (which we already got a fair amount of them), we can modify our recommendations.

But guess what?! We still don’t have all the answers! There are so many unknowns in nutrition science!

And for this reason I advocate a conservative approach: don’t go wild until you know for sure what you’re doing! The further a certain diet deviates from traditional ways of eating (as they were before the epidemic of lifestyle diseases), the more it needs to give us solid, science backed evidence that it’s valid, the more burden of proof it has. Or as Carl Sagan said:

“Extraordinary claims require extraordinary evidence.”

The more a diet deviates from traditional ways of eating the more extraordinary it is – and therefore the higher quality scientific evidence it needs to be backed with before it can be accepted or recommended.

For this reason, one needs to be wary of any diets that are radically different from our traditional ways of eating, especially if they:

  • skip entire food groups or are based just on few types of food
  • recommend odd ratios of macronutrients, such as no carbs at all, or very high fat, or very low fat, or very high protein… or any other combination that is unusual
  • claim that certain groups of food are toxic or poison, in spite of people consuming them for centuries with no ill effects
  • advocate extreme amounts of certain types of food…

Now, we’ve been talking a lot about common sense and why big deviations from traditional ways of eating can be dangerous. But we didn’t talk much about the results that nutrition science has already given us. What to do with them? Easy: use them! These scientists haven’t been doing science in vain, but so that people can benefit from their results. Even though there are still countless unknowns in nutrition science, there are also, many, many knowns.

And for this reason, one should also be wary of any and all diets that ignore what science has already said. For example, any diet that recommends unrestricted consumption of red meat and saturated fats needs to be scrutinized. And I say scrutinized, not outright rejected. Because the evidence for damaging effects of red meat and saturated fats when consumed in large quantities exists, but it isn’t as rock solid as one might think. But it is still strong enough to merit recommending limiting these substances (red meat and saturated fat) in your diet. Not excluding them from your diet, just limiting their intake. And this is what I recommend too: limiting red meats and saturated fats.

To sum it all up:

Nutrition can’t be completely evidence based, becasue science hasn’t and can’t even in theory know it all. Without having scientific results our best guess is to base our diet on traditional ways of eating as they existed just before the arrival of the epidemic of lifestyle diseases, either from your own country, or from any region in the world known for good health or longevity. As soon as science, however, gives us some results, we need to incorporate them in our dietary recommendations – or in other words: we should not ignore good science.

Also: You should be wary of any diet that is radically different from traditional ways of eating. The weirder the diet is, the stronger scientific evidence it needs to have in order to be accepted.

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