One of the more pernicious influences of our biases is that they tend to cause us to perceive biases in others, whether or not they are there. So, for instance, my colleagues who contend that vegan eating is unrivaled for health tend to think I am biased against it -- because my conclusion is far more tempered. My colleagues who advocate for Paleo eating seem to find me biased against that when I point out that mammoth is hard to find these days, and there were no Stone Age salamis.
Actually, though, my particular bias is not in favor of any given dietary pattern; it's in favor of epidemiology. I don't care that much about advocating for any given diet, but I do care about the weight of evidence, and advocating for the "truth," as best we know it. This principle applies not only to my food for thought, but my food as well. When the available evidence (or prevailing interpretation of it) inveighed against dietary fat and eggs, for instance, my diet was very low-fat and egg-free. As that thinking has evolved, I have added the occasional (free-range, organic) egg and healthy oils back into my diet.
So, to the extent a human being can be bias-free about diet, I try to be. Certainly, I favor epidemiology over ideology, and try diligently to base my conclusions and recommendations on the weight of evidence.
On that basis, I contend that a diet of diverse, mostly whole and wholesome plant foods represents that theme of optimal eating for health. There is plenty of room for variation on that theme -- which among other things, provides you and your family the latitude required to choose what you like, and love the food that loves you back. Note that even a Paleo diet, applied with reasonable fidelity, is a diet of diverse, mostly whole and wholesome plant foods. Paleoanthropologists suggest that some 50 percent of our Stone Age ancestors' calories came from plants. Given that animal foods are generally much more energy dense than plant foods, a diet of 50 percent plant calories is, by volume, still a diet of mostly plants.
If I do have a bias about healthful eating, it's that our health cannot and should not be achieved at the expense of the Earth. Whatever the arguments for mostly meat-based diets, for instance, they start to fall apart rather quickly in a world of over 7 billion of us. Leaving aside the important nutritional distinctions between antelope and bacon cheeseburgers, we may simply focus on the profound distinction between roaming, isolated bands of hunter-gatherers surrounded by vast and pristine spaces -- and the modern world.
Even if Homo sapiens were constitutional carnivores, which we clearly are not, we would be obligated to adapt to a population density that no longer allows for that practice. Given we are constitutional omnivores, there is no biological barrier to embracing diets of food, not too much, mostly plants.
We all have common reason to do just that. Namely, the common ground of our home planet. The environmental, ecological, and ethical costs of preferential meat consumption are all very high for a population of more than 7 billion. The water expenditure alone makes the practice dubious, if not disastrous, in an increasingly thirsty world.
I concede without reluctance that an authentically "Paleo" diet (ideally, in conjunction with other elements of a Paleo lifestyle) figures among contenders for best diet laurels. I am not convinced that is true of certain other carnivorously inclined platforms, but perhaps you are. My point today, on Earth Day, is that it doesn't matter if meat-based eating is good or even best for human health. It doesn't work in modern context. We can't have our population in excess of 7 billion, and eat our daily side of beef, too.
I know -- the libertarians are protesting. I hear you: "What I eat for dinner is my own damn business!" And right you are. But then again, my inalienable right to swing a stick ends where your nose begins, and much the same may pertain when the dinner bell tolls. If 7 billion rugged individualists eat whatever they like, the result may well be no water for Californians, let alone the Sudanese. I didn't make these rules -- I'm just paying attention, and my cup of water is half empty at best.
The basic care and feeding of Homo sapiens, a perennially and excessively contentious issue, requires adjudication in context. The context of modern living on a rather crowded planet imposes ineluctable constraints on the dietary patterns that are both salutary, and sustainable. Call it bias if you like, but I would like my grandchildren to be able to see a forest, let alone a tree -- and to get a glass of water when thirsty.
It's Earth Day, with corresponding food for thought on the menu. We are all invited to chew on it accordingly.
Dr. David L. Katz has authored three editions of a leading nutrition textbook. He iseditor-in-chief of the peer-reviewed journal, Childhood Obesity, and President of the American College of Lifestyle Medicine. He is the author of Disease Proof, and most recently, of the epic novel, reVision.