More problems with the paleodiet

In my Anthropology of Food class we have spent the past two weeks talking about the technological, dietary, cultural and population health transitions from the late Paleolithic, through the origin of agriculture, to present-day industrial-scale food production, with much of the discussion focused on what constitutes “good food” and the “right” kind of food production. The conversations are fascinating because of the multitude of perspectives and approaches you can take to these questions. The conversations have also got me thinking again about evolutionary diet issues and the paleodiet.

Back in the summer I had a post on the problems with the paleodiet. One of my complaints was on the notion that there is a–emphasis on the singular–paleodiet. As Pat Shipman appropriately pointed out in the comments to a follow-up post on meat and the paleodiet, when in time is the “paleo” of paleodiet. Do we mean the tropical forest diet of our ape ancestors seven million years in the past? Do we mean the shift towards a higher proportion of high-quality food items with the transition from Australopithecus to Homo about two million years ago? Or do we mean the co-evolution of humans and domesticated food production over the past 10,000 years?

Conveniently, I picked and chose from all of these options over the weekend. After a morning run with my dogs on Sunday I had an orange (ape diet) and a bowl of cereal (agricultural human diet). Later in the day I made some pork tenderloin (Pleistocene Homo diet, pretending that domesticated pigs existed during the Pleistocene) for the family, with a side of pasta (agricultural human diet) and some grapes (ape diet) for desert. I do not think my menu was particularly unusual by American standards and was variously paleo depending on your point of view. This gets at another theme from the comments to those posts, which is what constitutes the real “paleodiet” today. Is it a high percentage of calories from lean-protein sources? Or is it the consumption of a greater fraction of unprocessed, or “natural” food items?

This is not an atheoretical issue, however. It is possible to approach the question of what we are supposed to eat from an evolutionary perspective (a related issue that I hope to get to in the near future is the question of whether we should approach this from an evolutionary perspective). The starting point for such a discussion begins by recognizing that individuals interested in optimizing their health through dietary changes are not really interested in the evolutionary question. Evolution has not operated to optimize human health. In the currency of evolution, survival to and through reproduction, health is merely a correlated threshold variable. You only need to be “healthy enough” to survive and have kids. The added benefits of being able to do that and, say, run a marathon in less than 3 hours, are likely marginal from an evolutionary perspective.

Human physiology is pretty good at “getting by,” evidenced by the broad range of environments, diets, and conditions in which humans survive and thrive today. Human cultural capabilities play a big role in adding to the plasticity of human experience. Thus, evolution will operate most effectively on aspects of diet, metabolism and related physiology on areas that directly impact reproductive health, early development and survival (Peter Ellison has a useful review of energetics and reproductive ecology in Paleoanthropology).

So if an evolutionary perspective on diet is focused on optimizing evolutionary fitness rather than human health, can we still theorize a maximally healthy evolutionary diet? This requires even further clarification of terms. Is optimal health evidenced by optimal performance (you can think of this as the cross-fit perspective), maximum longevity (the immortality perspective), or a balance of longevity and performance (the Golden Girls perspective?

Someone looking to lower their cholesterol might be aiming for a very different optima than someone looking to lose 20 pounds or someone hoping to avoid prostate cancer. In each case the “right” combination of foods is likely to vary based on the genetic/ancestral background they bring with them, the specifics of their own cultural and biological development, and the realities of their current life and activity level.

And here is where I return to one of my initial statements.

The best evolutionary advice I could provide on diet is to go with what works…Your body is a better judge of what diet is right for you than any book or diet you can buy.

Engaging evolution to achieve maximum health is co-opting a system designed for a related purpose (survival and reproduction) for a personalized result. Peak sensitivities in the adaptive landscape surrounding human diet are focused on issues only partially related to health. This means that there are likely many local optima in terms of dietary health depending on what aspects of health you seek to engage and your own individual background.