Over the course of the last few months I’ve received an education in the science of human nutrition from www.wholehealthsource.blogspot.com. It is written by Stephan Guyenet, a recently anointed Ph.D. in neurobiology and currently a researcher on neurodegenerative diseases. Since his blog has been the most important influence in transforming my view of nutrition and, after long consideration, my actual diet as well—I’ve decided to share an overview of it.
This guy runs one of the best nutrition sites out there. His philosophy is grounded in very simple historical and comparative observations of human health in different societies with different diets. To refine and supplement this anthropological/observational information, he independently analyzes contemporary scientific studies of human nutrition—with an emphasis on quality intervention studies (the only ones that count).
The human societies which consistently evince the best health outcomes are those which adhere to a hunter-gatherer (H-G) diet (called the “Paleo diet”). The archaeological record provides considerable evidence of this. There does not seem to be much dispute among the experts that human health declined, in a variety of ways, with the advent of agriculture. Additionally, in the last century, modern observation and testing of H-Gs who continued to follow traditional diets reinforced this historical evidence. The diseases of civilization, in particular cardiovascular disease and cancer (but also a number of less serious conditions), are much rarer among H-Gs than among westerners of the same age. This result holds regardless of the specific dietary composition of a given society, so long as they are hunter-gatherers. And the variation in diet between different H-G societies is extreme.
Remember, among all the groups I will mention in the ensuing examples, these diseases of civilization are virtually unheard of. Traditionally, Inuit relied upon animal food to provide 95% of their calories; and 70%+ came from animal fat. In contrast, the Kitavans, currently resident in the South Pacific, derive 70% of their calories from carbohydrates and 70% smoke cigarettes (but no heart attacks were found in the population). Traditional Masai, cow herders in southern Africa, lived on a diet of fermented whole raw milk, cow blood, meat and organs, and herbs—this amounts to 70% fat, 35% saturated fat, and, like the Inuit, 5% of calories from plant sources. The traditional Masai do not know what a heart attack is, do not recognize the symptoms, show no clinical signs of heart attacks. Fifty were autopsied recently, about a third of them over 50 years old, and, though those who were no longer following a strict traditional diet had atherosclerosis, not one had had a heart attack. Unlike the Kitavans the Tokelauans, another group in the south Pacific, consume a high fat diet: 50-60% fat, including 40-50% of all calories as saturated fat (from coconuts), the highest saturated fat consumption yet found in any traditional society. In 1982, all Tokelauan men aged 40-69 were given ECGs and none showed signs of prior heart attack—but 3.5% of Alabamans of the same age show signs of prior heart attack. I suppose it’s worth adding that the exercise levels in these groups vary greatly, from the Masai who do a lot of walking to the Kitavans, whose activity level is comparable to a modern European. In other words, there is good reason to believe that exercise is not the key factor. Diet is. A diet that has flown off the evolutionary rails causes diseases of civilization.
Stephan goes through the epidemiological studies from which the above data is derived. The point isn’t simply to advocate a high fat or a carnivorous diet, since groups like the Kitavans have relatively low fat and less carnivorous diets (though all known hunter-gatherer groups consume animal foods and the average intake among the 229 known groups analyzed by Loren Cordain is 50% of calories from animals and fish--although, it's well to note that most of these societies have veered away from a pure H-G lifestyle to some degree). The lesson to be drawn here, the element that all these healthy societies have in common, along with all known historical and current hunter-gatherers—is what they do not eat. Hunter-Gatherers do not eat grains, refined sugars, industrial vegetable oils, or food additives and chemicals. Instead, they eat, in greatly varying proportions, depending upon the availability in their environment: meat (always including organs), vegetables (esp. tubers and other root vegetables with high calorie counts), seafood, fruit, nuts, insects, herbs—on average, in that order from most to least calories.
The reason postulated for the apparent ill effects of the foods on the “do not eat” list is that humans have not evolved to eat them. Human evolution is a slow process of competitive adaptation to a constantly changing environment. Various forms of the hunter-gatherer diet have been followed by humans and our direct evolutionary ancestors for 2 million years--sufficient time to evolve optimal fitness for this diet. But, grains were only first domesticated 10,000 years ago. And the majority of humanity probably wasn’t eating them until 5,000 years ago. That is 5,000 years of evolutionary adaptation vs. 2 million years. Even the 10,000 Year Explosion of Cochran and Harpending does not nullify this argument, though it does somewhat attenuate it. Refined sugars are still more recent. As for industrial vegetable oils and food chemicals, they were the products of the 20th century—a circumstance that has permitted virtually no evolutionary adaptation. We are not adapted to these foods. In some cases this is obvious: for example, most of the world is lactose intolerant because they have not had sufficient time to adapt to cow milk. This example is also useful as an illustration that evolution, per Cochran and Harpending, does not stop: some humans evolved lactose tolerance in the last few thousand years. A further complication is that consuming pasteurized milk is different from fresh or fermented raw whole milk--also, consuming the latest breeds of wheat prepared by the food industry is different from consuming traditional einkorn wheat prepared in traditional ways. Those who consume foods developed in Neolithic times endanger their health to one degree or another. This is where Stephan starts; this is the first element of his nutritional philosophy, a clearly defined apprehension of what foods are presumptively safe and what foods are questionable.
From this epidemiological-evolutionary foundation, he then analyzes the scientific literature on nutrition. The simplest approach is to determine which of the hunter-gatherer dietary options might be healthiest and why. Also, this approach begs the question: why should we confine ourselves only to this set of options, the known range of H-G diets? This represents a shrewd humility in face of considerable scientific ignorance of human nutrition. Human physiology is an enormously complex system with a virtually infinite number of variables. Many of these variables are effectively unknown, as are their interactions. Scientists find it difficult to generate useful conclusions from such an irreducible chaos of information. Given the level of complexity and chaos, I would even venture that we will never develop a total understanding of human biology. We may instead, to achieve progress, eventually pursue simplification by means of transforming ourselves, piece by piece, into cyborgs. But, the point is, the most useful evidence we have to discover optimal nutrition is the signposts left by the evolutionary process. Evolution has done much of the work for us over thousands of generations of trial and error. Science, for now, remains a comparatively weak resource in this area and ought be seen, for practical purposes, as the handmaiden of evolutionary reasoning.
Another aspect he covers occasionally are the practical challenges of adopting a Paleo diet in 21st century America. It’s neither easy nor particularly cheap to do it right. Also, it can be difficult to decide which type of Paleo diet to pursue—though personal tastes, finances, convenience, digestive idiosyncrasies, and other factors tend to narrow it down quite a bit before arbitrary choices arise.
There are a great many blogs on the Paleo diet; and Stephan has many important predecessors (Weston Price being his acknowledged favorite) and competent contemporaries (Gary Taubes seems to be one of the most significant). I find the following blogs quite useful also (the first has an excellent twelve-step summary of how to follow a paleo diet--though many paleo advocates would argue that a higher intake of quality carbs is harmless):
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