A Thumbs Down Book Review
Nutrition and Evolution
By Michael Crawford and David Marsh
Review by Sally Fallon
We hate to give this book a Thumbs Down as it contains a fascinating and important discussion of the essential role that animal foods play in human diets. The fact that the authors end up by condemning butter and recommending commercial vegetable oils shows how political correctness can lure modern writers down the wrong path, forcing them into conclusions that completely contradict the major premises of their argument.
The thesis of Crawford and Marsh is that exposure to the appropriate chemistry allows the various species to develop. Animals could not develop on the earth until plants had produced enough oxygen for them to survive.
A major difference between the carnivore and the herbivore is the design of the eye–a difference that is explained by the availability of nutrients to the two categories of animals. Carnivores like cats and owls–and humans–are amazingly efficient in dealing with different degrees of light. Our eyes can see a small light on a dark night miles away and also adjust to see clearly in a bright light. Why is it that animals that are preyed upon, like antelope and mice, do not have this range of vision, even though it would be to their evolutionary advantage?
The answer comes from the availability of vitamin A in the diets. The first sign of a vitamin A deficiency is failing night vision. Crawford and Marsh point out that this was discovered after the First World War in Denmark, when the country exported all of its butter to earn foreign exchange, using margarine for home consumption. Many Danish children developed blindness, a tragic occurrence that led to the fortification of margarine with vitamin A. (Even consumpton of fortified margarine can lead to poor eyesight, because margarine lacks very long-chain omega-3 fatty acids and the trans fats it contains can interfere with visual development.) Herbivores make some vitamin A from carotenes in the plants that they eat, but predators get preformed vitamin A from the organ meats of their prey, which they eat preferentially. In fact, cats, the ultimate predators, cannot make vitamin A from carotenes at all.
There is a limit, say the authors, to the level of organization that any particular animal can achieve and also to what it can pass on through its genes. Many genes are required for an animal to be able to make vitamin A. If a cat had to synthesize its own vitamin A, it would take up a significant amount of “disk space,” to use terminology from the realm of computers. Instead, cats delegate the complex vitamin-A-conversion process to their prey. “At one meal, they can take in the whole supply of vitamin A that their victim has accumulated over a lifetime, and do so at low cost to their own organization.”
It is delegation of this kind that has allowed the whole hierarchy of animal life to build up. Like cats, humans must rely on lower orders of animals for vitamin A, for complete protein, and for essential fatty acids and their elongated forms. We need these components in our diet today as much as we did in the past, because our genetic makeup has not changed.
Obviously, new components in the diet, like sugar and white flour, are a prime contributor to disease. But Crawford and Marsh mention these in passing, preferring to dwell on the dubious differences between wild and domestic animals. They wrongly assert that the meat of wild animals is low in saturated fat and high in polyunsaturates, and that wild animals do not accumulate body fat. Formerly butter was a food for the rich, they say (after noting that butter was a common food in Denmark), and not part of the diet of the common man.
So along with sugar and white flour in modern diets, the authors finger saturated fats as something new and detrimental. In fact, it is the polyunsaturated vegetable oils they recommend that are new and detrimental, not stable saturated fats. They claim that saturated fats (and sugars and carbohydrates which are converted to saturated fats) “swamp the essential fats. . . and then reduce their amounts” resulting in “vascular, nervous and immune system disorders.” In fact, saturated fats support the body’s use of the essential fatty acids and facilitate their conversion into the elongated forms. Furthermore, saturated fats like butter contain vitamin A, which humans can make only with great difficulty.
Nowhere is the schizophrenic logic of this book more evident than in the discussion of Weston Price. The fine dental health and bone structure of primitive peoples–including those consuming butter and domesticated meat–is described in detail, and Price’s emphasis on the high human requirements for vitamin A duly noted. This is followed by a lament for the increased levels of fat “from milk, meat, butter and margarine” in the Japanese diet, which the authors assert is the cause of the “changes in body and facial shape” in Japan. Crawford and Marsh seem oblivious to the fact that the decline in health and degeneration in facial form in America has occurred during the same period in which we have substituted margarine and vegetable oil for butter, lard and other nutrient-dense animal fats.
What can give man hope, say the authors, “is that he alone can look back and see what made him, and look forward to gauge what that knowledge implies for his future.” Let us look back with the discerning eye of well nourished carnivores, and not with the confused vision of those brought up on vegetable oils.
This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly magazine of the Weston A. Price Foundation, Summer 2002.