Wednesday, 17 February 2016

Paleo is Illogical but Maybe it is Still Healthy

When I first heard about the paleo diet's motivating principle, I was several notches short of impressed. The idea that we should eat what our ancestor's ate because it allegedly worked so well for them seemed to me to be a great joke. Here are a few reasons.

First of all, life expectancy back in the good old dietary days was quite a bit shorter than today. It's not like they lived an optimal lifestyle and now, with the addition of bread, we can barely live to middle age; the life of our paleolithic ancestors was best described by Hobbes as "solitary, poor, nasty, brutish, and short" (though he was not exactly talking about nutrition). It is true: modern humans live in a globalised community, are on average far richer, have developed more pro-social behaviour and live substantially longer than our cave-dwelling ancestors. But, if you would rather go back then, go for it. Of course, I am under no illusion that paleo dieters want to actually live like cavemen, just eat like them. But still, they were hardly paradigm cases of longevity, granted they did eat healthier than the standard Western diet.

Even if they were extraordinarily healthy, are paleo dieters willing to go authentically paleo with their lifestyle? I can guarantee that paleolithic humans did not sit around counting calories, but I can also guarantee they burnt far more than almost anyone. There is quite a difference between scavenging and hunting for every morsel and scrap of food in their time and sneaking in a quick trip to the gym between bouts of sitting at a desk or on the couch. Maybe the paleo diet is the healthiest diet around if you spend almost all your waking hours walking, hunting, crawling and moving about.

So people do not live paleo lifestyles. Actually, they do not eat paleo diets, either. Apart from the more obvious cases (does anyone really think paleo muffins grow on treas?), the cartoonish version of paleo diets that is emulated by contemporary paleo dieters never really existed. Let me give an example from the first result I got when I searched for "Paleo Diet:"
Daily Sample Straight from Dr. Cordain’s The Paleo Answer:
  • Breakfast: Omega-3 or free ranging eggs scrambled in olive oil with chopped parsley. Grapefruit, or any fresh fruit in season, herbal tea
  • Snack: Sliced lean beef, fresh apricots or seasonal fruit
  • Lunch: Caesar salad with chicken (olive oil and lemon dressing), herbal tea
  • Snack: Apple slices, raw walnuts
  • Dinner: Tomato and avocado slices; grilled skinless turkey breast; steamed broccoli, carrots, and artichoke; bowl of fresh blueberries, raisins, and almonds; one glass white wine or mineral water. (Clearly, wine would never have been available to our ancestors, but the 85:15 rule allows you to consume three non-Paleo meals per week.)
Somehow, Dr Cordain seems to think that our ancestors got up, wandered over to their ancient stove and scrambled from their abundant stores of eggs (?) with their recently pressed olive oil (?) and parsley that happened to be on a nearby bush. Remember, the whole idea is that our diet went downhill when we started raising our own crops and animals. But it gets worse: practically every meal is a meat-lovers dream, indicating that our ancestors managed to find and kill a cow, a chicken (not before getting plenty of unfertilised eggs) and a turkey. Let's ignore that our ancestors probably couldn't have a cheat meal on the diet they were forced to eat by food availability.

In reality, we are entirely sure what they ate because they forgot to bequeath us any food logs. Our best bet is to guess from non-westernised populations that exist today and try and evaluate what remaining hunter-gatherer populations still survive. Of the ones that survive, it is crucial to remember that they survived. They were not wiped out by food shortage, a major feature of their lives which made agriculture so revolutionary.

Perhaps the closest population to paleolithic diets (in plural: their undoubtedly existed major variation regionally) is the Kitavan people. Whilst, as I said, their life expectancy is short (around 45 years of age), the ones that do live longer seem to enjoy a high quality of life into old age. But unlike Dr Cordain's suggestions, the Kitavans eat minimal (if any) land-based meat and around 70% carbohydrates coming from fruit and root vegetables primarily. They eat about 10% protein, a shockingly low amount compared to the above suggested "paleo" diet.

It might be objected that there are plenty of high-meat populations eating non-western diets, like the Maasai. This population seems to be polar opposite to the Kitavans (remember how I said that ancient diets would have been incredibly diverse?) with plenty of meat and milk (woops! Did they not get the memo that milk is non-paleo?). Even ignoring the crucial importance of non-paleo milk in their diet - mind you, their milk is unlike wimpy Western milk, with way more fat, cholesterol and protein, with less lactose - one important feature of the Maasai diet is that it contains barely any vegetables. Still not what today would pass for a paleo diet.

Perhaps a diet derived from our ancestors would have been basically vegetarian? I could go on with other populations that may be closer to the paleolithic times than us, but the point is that none of them ate what would today be considered a good paleo diet. Nor could we hope to emulate it in any practical sense today, since our food is not the same anyway. Just like the Maasai milk is not like our milk, our domesticated animals are not like paleolithic animals, our soils are not like the more nutrient rich paleolithic soils and our crops have been genetically modified by natural breeding for so long that we might not even recognise their paleolithic precursors - for instance, did you know that carrots were originally not orange?

At this point, paleo aficionados might be screeching that I am completely ignoring their main argument: nobody is saying to go back to the paleo diet just because, rather, the claim is that the paleo diet is better because we have evolved to eat it. This is problematic on all sorts of levels.

The first thought I had when I originally heard this claim was "so we must have evolved to love McDonald's" and I stand by that thought. Highly processed sugar and fat laden foods must be good for us, on this evolutionary view, because we evolved to want it so much. We never evolved to want dirt because dirt wasn't nutritious; our taste buds evolved to give us pleasure when we eat foods the body wants, and is at least neutral - if not disgusted - by foods we should avoid. The correlation between poisons and bitterness is not accidental, it is evolved. So given any possible food, this line of evolutionary thought would lead us to conclude that the standard Western diet is the best one, because only in the developed West with our panoply of culinary choice in supermarkets do we get close to being able to choose any possible food.

It is exactly this desire for the so-called unhealthy foods that led us to develop these foods, and at bottom, it is why the much maligned agricultural revolution took off. Granting the obviously true point that it is only now that we have been able to create these Frankenstein foods which mess with our in-built biology, agriculture cannot have led to a diet that kills us because we have been using agriculture for years without dying.

It is a trivially true evolutionary fact that the populations which developed agriculture out-competed the ones that did not. In other words, nature has cast her vote: agriculture beats non-agriculture in an evolutionary sense. However, even this is not an argument for agriculture being the best basis for a healthy diet because evolution is complicated and an enormous number of other variables exist.

It is crucial to understand how evolution works to see how misguided evolution-based arguments are for establishing nutritional facts. Evolution is slow - that is exactly the point raised - and it is so slow that it never reaches its end. Paleolithic humans were not built for whatever diet they ate, necessarily, since they evolved themselves from more primitive creates - ultimately, we all come from single-cell organisms! Natural selection works with what it gets and adaptations slowly add up to provide the best system given the circumstances.

One thing we learn from our evolutionary past is that, at bottom, humans are experts at making do with what we get. We are not built meat eaters, or vegans, or anything of the sort; we are scavengers. That is why so many varied diets seem to work. It is true that milk is not a staple of evolutionarily ancient diets, but we adapted to digesting lactose and some groups have managed to thrive from it. It is true that grains were not mainstays of ancestral diets, but most people can tolerate proteins like gluten just fine.

Paleo logic might work in cases like eating more fiber (because our digestive system would be adapted to "assuming" a high fiber intake), it successfully predicts that we might not have a limit on our sugar appetite (because sugar was scarce and all natural anyway back then) and it may imply that we are less likely to have defences for newer toxins than for older ones.

At the end of the day, the paleo diet may still be the healthiest diet. I am far from arguing against people eating the paleo diet. If what I say is true, in fact, you may do just fine on it. At bottom, whether or not the paleo diet works, it does so regardless of whether paleo logic is sound.

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