« Reading List: Path of the Assassin | Main | Reading List: American Assassin »

Monday, December 20, 2010

Reading List: The Paleo Diet

Cordain, Loren. The Paleo Diet. Hoboken, NJ: John Wiley & Sons, 2002. ISBN 978-0-470-91302-4.
As the author of a diet book, I don't read many self-described “diet books”. First of all, I'm satisfied with the approach to weight management described in my own book; second, I don't need to lose weight; and third, I find most “diet books” built around gimmicks with little justification in biology and prone to prescribe regimes that few people are likely to stick with long enough to achieve their goal. What motivated me to read this book was a talk by Michael Rose at the First Personalized Life Extension Conference in which he mentioned the concept and this book not in conjunction with weight reduction but rather the extension of healthy lifespan in humans. Rose's argument, which is grounded in evolutionary biology and paleoanthropology, is somewhat subtle and well summarised in this article.

At the core of Rose's argument and that of the present book is the observation that while the human genome is barely different from that of human hunter-gatherers a million years ago, our present-day population has had at most 200 to 500 generations to adapt to the very different diet which emerged with the introduction of agriculture and animal husbandry. From an evolutionary standpoint, this is a relatively short time for adaptation and, here is the key thing (argued by Rose, but not in this book), even if modern humans had evolved adaptations to the agricultural diet (as in some cases they clearly have, lactose tolerance persisting into adulthood being one obvious example), those adaptations will not, from the simple mechanism of evolution, select out diseases caused by the new diet which only manifest themselves after the age of last reproduction in the population. So, if eating the agricultural diet (not to mention the horrors we've invented in the last century) were the cause of late-onset diseases such as cancer, cardiovascular problems, and type 2 diabetes, then evolution would have done nothing to select out the genes responsible for them, since these diseases strike most people after the age at which they've already passed on their genes to their children. Consequently, while it may be fine for young people to eat grain, dairy products, and other agricultural era innovations, folks over the age of forty may be asking for trouble by consuming foods which evolution hasn't had the chance to mold their genomes to tolerate. People whose ancestors shifted to the agricultural lifestyle much more recently, including many of African and aboriginal descent, have little or no adaptation to the agricultural diet, and may experience problems even earlier in life.

In this book, the author doesn't make these fine distinctions but rather argues that everybody can benefit from a diet resembling that which the vast majority of our ancestors—hunter-gatherers predating the advent of sedentary agriculture—ate, and to which evolution has molded our genome over that long expanse of time. This is not a “diet book” in the sense of a rigid plan for losing weight. Instead, it is a manual for adopting a lifestyle, based entirely upon non-exotic foods readily available at the supermarket, which approximates the mix of nutrients consumed by our distant ancestors. There are the usual meal plans and recipes, but the bulk of the book is a thorough survey, with extensive citations to the scientific literature, of what hunter-gatherers actually ate, the links scientists have found between the composition of the modern diet and the emergence of “diseases of civilisation” among populations that have transitioned to it in historical times, and the evidence for specific deleterious effects of major components of the modern diet such as grains and dairy products.

Not to over-simplify, but you can go a long way toward the ancestral diet simply by going to the store with an “anti-shopping list” of things not to buy, principally:

  • Grain, or anything derived from grains (bread, pasta, rice, corn)
  • Dairy products (milk, cheese, butter)
  • Fatty meats (bacon, marbled beef)
  • Starchy tuber crops (potatoes, sweet potatoes)
  • Salt or processed foods with added salt
  • Refined sugar or processed foods with added sugar
  • Oils with a high omega 6 to omega 3 ratio (safflower, peanut)

And basically, that's it! Apart from the list above you can buy whatever you want, eat it whenever you like in whatever quantity you wish, and the author asserts that if you're overweight you'll soon see your weight dropping toward your optimal weight, a variety of digestive and other problems will begin to clear up, you'll have more energy and a more consistent energy level throughout the day, and that you'll sleep better. Oh, and your chances of contracting cancer, diabetes, or cardiovascular disease will be dramatically reduced.

In practise, this means eating a lot of lean meat, seafood, fresh fruit and fresh vegetables, and nuts. As the author points out, even if you have a mound of cooked boneless chicken breasts, broccoli, and apples on the table before you, you're far less likely to pig out on them compared to, say, a pile of doughnuts, because the natural foods don't give you the immediate blood sugar hit the highly glycemic processed food does. And even if you do overindulge, the caloric density in the natural foods is so much lower your jaw will get tired chewing or your gut will bust before you can go way over your calorie requirements.

Now, if even if the science is sound (there are hundreds of citations of peer reviewed publications in the bibliography, but then nutritionists are forever publishing contradictory “studies” on any topic you can imagine, and in any case epidemiology cannot establish causation) and the benefits from adopting this diet are as immediate, dramatic, and important for long-term health, a lot of people are going to have trouble with what is recommended here. Food is a lot more to humans and other species (as anybody who's had a “picky eater” cat can testify) than just molecular fuel and construction material for our bodies. Our meals nourish the soul as well as the body, and among humans shared meals are a fundamental part of our social interaction which evolution has doubtless had time to write into our genes. If you go back and look at that list of things not to eat, you'll probably discover that just about any “comfort food” you cherish probably runs afoul of one or more of the forbidden ingredients. This means that contemplating the adoption of this diet as a permanent lifestyle change can look pretty grim, unless or until you find suitable replacements that thread among the constraints. The recipes presented here are interesting, but still come across to me (not having tried them) as pretty Spartan. And recall that even Spartans lived a pretty sybaritic lifestyle compared to your average hunter-gatherer band. But, hey, peach fuzz is entirely cool!

The view of the mechanics of weight loss and gain and the interaction between exercise and weight reduction presented here is essentially 100% compatible with my own in The Hacker's Diet.

This was intriguing enough that I decided to give it a try starting a couple of weeks ago. (I have been adhering, more or less, to the food selection guidelines, but not the detailed meal plans.) The results so far are intriguing but, at this early date, inconclusive. The most dramatic effect was an almost immediate (within the first three days) crash in my always-pesky high blood pressure. This may be due entirely to putting away the salt shaker (an implement of which I have been inordinately fond since childhood), but whatever the cause, it's taken about 20 points off the systolic and 10 off the diastolic, throughout the day. Second, I've seen a consistent downward bias in my weight. Now, as I said, I didn't try this diet to lose weight (although I could drop a few kilos and still be within the target band for my height and build, and wouldn't mind doing so). In any case, these are short-term results and may include transient adaptation effects. I haven't been hungry for a moment nor have I experienced any specific cravings (except the second-order kind for popcorn with a movie). It remains to be seen what will happen when I next attend a Swiss party and have to explain that I don't eat cheese.

This is a very interesting nutritional thesis, backed by a wealth of impressive research of which I was previously unaware. It flies in the face of much of the conventional wisdom on diet and nutrition, and yet viewed from the standpoint of evolution, it makes a lot of sense. You will find the case persuasively put here and perhaps be tempted to give it a try.

Posted at December 20, 2010 22:30