Have you heard of the Paleo Diet? It has been an increasingly popular diet/lifestyle "movement" for some time now, and recently it has come under some sustained fire in the press. A book, Paleofantasy: What Evolution Really Tells Us about Sex, Diet and How We Live by biologist Marlene Zuk, takes aim at the unorthodox approach to human health advocated by paleo enthusiasts. A post by Ferris Jabr at Scientific American provides context for the disagreement, and seconds Zuk's harsh critique. First, a bit about what Paleo is, according to Jabr:
Proponents of the Paleo diet follow a nutritional plan based on the eating habits of our ancestors in the Paleolithic period, between 2.5 million and 10,000 years ago. Before agriculture and industry, humans presumably lived as hunter–gatherers: picking berry after berry off of bushes; digging up tumescent tubers; chasing mammals to the point of exhaustion; scavenging meat, fat and organs from animals that larger predators had killed; and eventually learning to fish with lines and hooks and hunt with spears, nets, bows and arrows.
But the Paleo diet bans more than just highly processed junk foods—in its most traditional form, it prohibits any kind of food unavailable to stone age hunter–gatherers, including dairy rich in calcium, grains replete with fiber, and vitamins and legumes packed with protein. The rationale for such constraint — in fact the entire premise of the Paleo diet — is, at best, only half correct. Because the human body adapted to life in the stone age, Paleo dieters argue—and because our genetics and anatomy have changed very little since then, they say — we should emulate the diets of our Paleo predecessors as closely as possible in order to be healthy. Obesity, heart disease, diabetes, cancer and many other "modern" diseases, the reasoning goes, result primarily from the incompatibility of our stone age anatomy with our contemporary way of eating.
Most nutritionists consent that the Paleo diet gets at least one thing right: cutting down on processed foods that have been highly modified from their raw state through various methods of preservation. Examples include white bread and other refined flour products, artificial cheese, certain cold cuts and packaged meats, potato chips, and sugary cereals. Such processed foods often offer less protein, fiber and iron than their unprocessed equivalents, and some are packed with sodium and preservatives that may increase the risk of heart disease and certain cancers.
First off, let's acknowledge that the cocksure self-righteousness of many paleo advocates is off-putting. But doesn't that paragraph concede that they have a point? Whole, unprocessed foods are the backbone of a healthy diet. I think that at this point, that statement is barely controversial. So why does this debate stir up such strong feelings?
At it's worst, Paleo is a codified set of health advice based on the best guesses of the dietary and lifestyle habits of our ancestors. When taken this way, it is pretty silly. Even if we wanted to eat like our ancient forbears, we probably couldn't do so — our food sources have changed dramatically over time. And the idea that we can't adapt to novel food sources is absurd — the sheer number of environments in which humans have thrived, all with incredibly diverse sources of nutrition, indicates that we can do well under an amazing array of circumstances. Humans have lived on seal blubber, on a diet prodominantly made of roots and everywhere in between. Bread is probably public enemy #1 for many paleo-ites; never mind that it has been pretty much the staple food source for western civilization.
But paleo has "evolved" considerably since it's early advocates rigidly built a diet around lean meats, fruits and vegetables. It is not really a presciptive system for a one-size-fits-all optimal diet. Rather, what it offers is a context in which to view human health and a suggestion that maybe we should consider the history of our species when trying to decide on our current lifestyles.
We live in an environment, and our choices, health status and well-being are in large part determined by the fit between our individual selves and our social, physical and cultural environments. The paleo approach in large part seeks to draw attention to the fact that our optimal environments — the diet and lifestyle factors in which we engage — are likely highly contingent on the environments of our ancestors.
This can help generate hypotheses about what may and may not be ideal. Following the logic of paleo thinking does not lead, by itself, to any convincing answers — it merely points to useful questions. Might it be possible that the widespread adoption of grains as food sources with the advent of agriculture was something the human body was not equipped to handle? Maybe. It's a theory. And the measure of a good theory is not the answers it provides, but the testable questions it raises. In this particular case, the answers are mixed. Certainly, gluten, a protien found in wheat, does not universally affect people negatively. However, it also seems clear that more folks are sensetive to gluten than were previously thought. Here is a rundown on non-celiac gluten insensitivity by Chris Kresser. That post is a great example of the usefulness of using logic popularized by "paleo" combined with thoughtful analysis and detailed inquiry into the current state of scientific research.
Paleo-ites will point out that eating salted, processed meat out of a can, shelf-stable cheese, and sugar filled pastry-like toaster-bound breakfast items are very new. On this, as I mentioned above, they are not far out on a limb.
If we really want to use the logic of adaptation and change and apply it to our current lifestyles, however, I don't think we need to go back to the days of the hunter-gatherers. Instead, we might be better off looking back just a few hundred years. The lifestyle changes that western societies, and increasingly, the rest of the world, have undergone since the industrial revolution dwarf anything that occured in the preceding millenia. Certainly Pop-tarts and hot dogs did not have a place on Thomas Jefferson's dinner table.
While humans can adapt to a dizzying array of foodstuffs, it is conceivable that the concentrated reductions of sugar, salt and fat that our industrialized systems of food processing throw at us are more than our systems can handle. They may even be somewhat addictive, depending how you define addiction.
The conclusion here is to reiterate this point of convergence yet again: that real food, prepared in the kitchen rather than a factory, is optimal for human health. This is entirely consistent with a "paleo" approach, but it does not really take a paleo approach to get there. In fact, it may be more efficient and accurate to base our diets on habits that are more like 300 years old. So while it has it's virtues, instead of a "Paleo" diet, we could talk about the "Agrarian Solution."