To judge whether the energy shortage experienced by raw-foodists is biologically significant, we need to know whether raw-induced weight loss interferes with critical functions—ideally, for a population living under conditions similar to those in our evolutionary past. In the Giessen study, the more raw food that women ate, the lower their BMI and the more likely they were to have partial or total amenorrhea. Among women eating totally raw diets, about 50 percent entirely ceased to menstruate. A further proportion, about 10 percent, suffered irregular menstrual cycles that left them unlikely to conceive. These figures are far higher than for women eating cooked food. Healthy women on cooked diets rarely fail to menstruate, whether or not they are vegetarian. But ovarian function predictably declines in women suffering from extreme energy depletion, such as marathoners and anorexics.
Raw-foodist men sometimes also report an impact on their sexual functions. In
How to Do the Raw Food Diet with Joy for Awesome Health and Success,
the author, Christopher Westra, wrote: “In my own experience, starting on living foods brought about a change in sexuality that was dramatic and completely unexpected. In just a few weeks, the number of times per day I thought about sex decreased tremendously.” Westra believed that seminal emissions are designed to remove toxins from the body. After a few weeks of a raw diet, he said, the intake of toxins had fallen to the point where ejaculation was no longer necessary. In a similar way some raw-foodists regard menstruation as a mechanism for removing toxins and therefore regard its cessation as a sign of the health of their diets. Perhaps it is unnecessary to note that medical science finds no support for the idea that toxins are removed by seminal emissions or menstruation.
Reduced reproductive function means that in our evolutionary past, raw-foodism would have been much less successful than the habit of eating cooked food. A rate of infertility greater than 50 percent, such as was found in the Giessen Raw Food study, would be devastating in a natural population of foragers. And since the Giessen study was of urban people enjoying a life of middle-class ease, such dramatic effects on reproduction are mild compared to what would have happened if these German raw-foodists had been searching for food in the wild.
Most raw-foodists prepare their food elaborately in ways that increase their energy value. Techniques include mild heating, blending, grinding, and sprouting. Any system of reducing the size of food particles, such as grinding and crushing, leads to predictable increases in energy gain. The German raw-foodists also had the advantage of eating oils produced commercially by industrial processing. Koebnick’s team found that about 30 percent of the subjects’ calories came from these lipids, a valuable energy source that would not have been available to hunter-gatherers. Yet even with all these helpful conditions, at least half the German women eating raw foods obtained so little energy from their diet, they were physiologically unable to have babies.
The Giessen subjects had further advantages. There is no indication that they engaged in much exercise, unlike women in foraging populations. Anthropologist Elizabeth Marshall Thomas describes bushman women in Africa’s Kalahari Desert returning to camp at the end of their ordinary long day thoroughly exhausted, because for much of the day they have been squatting and digging and walking, and hefting large loads of food, wood, and children. Even in populations that cook, these natural activity levels are high enough to interfere with reproductive function. If we imagine the lives of our German raw-foodists made more difficult by a daily regime of foraging for food in the wild, their rate of energy expenditure would surely be substantially increased. As a result, many more than 50 percent of the women would be incapable of pregnancy.
Then add that the subjects of the Giessen Raw Food study obtained their diets from supermarkets. Their foods were the typical products of modern farming—fruits, seeds, and vegetables all selected to be as delicious as possible. “Delicious” means high energy, because what people like are foods with low levels of indigestible fiber and high levels of soluble carbohydrates, such as sugars. Agricultural improvements have rendered fruits in a supermarket, such as apples, bananas, and strawberries, far higher in quality than their wild ancestors. In our laboratory at Harvard, nutritional biochemist NancyLou Conklin-Brittain finds that carrots contain as much sugar as the average wild fruit eaten by a chimpanzee in Kibale National Park in Uganda. But even carrots are better quality than a typical wild tropical fruit, because they have less fiber and fewer toxic compounds. If the German raw-foodists had been eating wild foods, their energy balance and reproductive performance would have been much lower than found by Koebnick’s team.
Supermarkets offer a year-round supply of the choicest foods, so the German raw-foodists had no seasonal shortages. Foragers, by contrast, cannot escape the tough times when sweet fruits, honey, or game meat become no more than occasional luxuries rather than daily pleasures. Even subsistence foods can then be hard to find. Anthropologist George Silberbauer reported that among the G/wi bushmen of the Central Kalahari, early summer was a time when all lost weight and everyone complained of hunger and thirst. In deserts like the Kalahari the result can be difficult indeed, but periodic shortages of energy like this are routine in all living hunter-gatherers, just as they are in rain-forest chimpanzees. Judging from studies of bones and teeth, which show in their fine structure the marks of nutritional stress, energy shortages were also universal in archaeological populations. Until the development of agriculture, it was the human fate to suffer regular periods of hunger—typically, it seems, for several weeks a year—even though they ate their food cooked.
Raw-foodism seems to be an increasingly popular habit, but if raw diets are so challenging, why do people like them? Raw-foodists are very enthusiastic about the health benefits, as described in books with such titles as
Self Healing Power! How to Tap Into the Great Power Within You.
They report a sense of well-being, better physical functioning, less bodily pain, more vitality, and improved emotional and social performance. There are claims of reductions in rheumatoid arthritis and fibromyalgia symptoms, less dental erosion, and improved antioxidant intake. Mostly such assertions have not been scientifically tested, but researchers have found improved serum cholesterol and triglyceride values.
Raw-foodists offer philosophical reasons too. “Natural nutrition is raw,” asserted Stephen Arlin, Fouad Dini, and David Wolfe in
Nature’s First Law
, a popular guide to raw-foodism. “It always has been. It always will be. . . . Cooked food is poison.” Many follow the pseudoscientific ideas of vegetarian Edward Howell, who theorized in a 1946 book that plants contain “living” or “active” enzymes, which, if eaten raw, operate for our benefit inside our bodies. His followers therefore prepare their foods below a certain temperature, normally about 45-48
o
C (113-118
o
F), above which the “life force” of the enzymes is supposedly destroyed. To scientists the idea that food enzymes contribute to digestion or cellular function in our bodies is nonsense because these molecules are themselves digested in our stomachs and small intestines. The “living enzyme” idea also ignores that even if food enzymes survived our digestive systems, their own specific metabolic functions are too specialized to allow them to do anything useful in our bodies. But while the idea of a “life force” in “living foods” is not accepted by physiologists, it persuades many raw-foodists to persist in their diet. By permitting some use of low heat, Howell’s philosophy also enables the “raw” food to be somewhat more palatable, easier to prepare, and more digestible than a truly unheated food would be.
Other raw-foodists are guided by moral principles. In 1813 the poet Percy Bysshe Shelley argued that meat eating was an appalling habit responsible for many of society’s ills and was obviously unnatural, given that humans lack claws, have blunt teeth, and dislike raw meat. Since he concluded that the invention of cooking was responsible for meat eating, and hence for such problems as “tyranny, superstition, commerce, and inequality,” he decided that humans were better off without cooking.
Instinctotherapists, a minority group among raw-foodists, believe that because we are closely related to apes we should model our eating behavior on theirs. In 2003 I had lunch with Roman Devivo and Antje Spors, whose book
Genefit Nutrition
argues that cooked food provides an unhealthy diet to which we are not adapted. They were lean and healthy. They were clear about their preference, which was to eat all their food not merely raw but without any preparation at all. They politely declined a salad because its ingredients had been chopped and mixed. The natural way, they explained, is to do what chimpanzees do. Just as those apes find only one kind of fruit when eating in a given tree, so we should eat only one kind of food in any meal.
To illustrate their habit, Devivo, Spors, and a friend had brought a basket containing a selection of organic foods. They sniffed at several fruits, one at a time, to allow their bodies to decide what would suit them best (“by instinct,” they said). One chose apples; another chose a pineapple. Each ate only his or her first choice. The third decided on a protein-rich food. He had brought frozen buffalo steaks and pieces of buffalo femur. Today was a marrow day. The femur chunks were the size of golf balls. Inside each was a cold pink mush that looked like strawberry ice cream. He cleaned out several pieces of bone with a teaspoon.
However strange it may be to think that we should eat to conserve living enzymes, or to reduce violence, or in the manner of apes, such concepts are helpful to raw-foodists because they bolster a strong commitment to principle. Eating raw intrudes into social life, demands a lot of time in the kitchen, and requires a strong will to resist the thought of cooked food. It can create personal problems, such as annoyingly frequent urination, and for meat eaters it increases the risk of eating toxins or pathogens that would be destroyed by cooking. There are other health risks too. Recent studies indicate that low bone mass in the backs and hips of raw-foodists was caused by their raw diet. Raw diets are also associated with low levels of vitamin B12, low levels of HDL cholesterol (the “good” cholesterol), and elevated levels of homocysteine (a suspected risk factor for cardiovascular disease).
In theory the precarious energy budgets experienced by the Giessen study subjects could be misleading. Maybe modern raw-foodists are so far removed from nutritional wisdom that they are just not choosing the right combination of foods. What about reliance on raw food in nonindustrialized cultures? This has often been reported. At the end of the nineteenth century, anthropologist William McGee, president of the National Geographical Society and cofounder of the American Anthropological Association, claimed that the Seri hunter-gatherers of northwestern Mexico ate meat and carrion largely raw. Four thousand years ago Sumerians in the Third Dynasty of Ur said that the bedouin of the western desert ate their food raw. As late as 2007, pygmies in Uganda’s Ruwenzori Mountains were reported in a national Ugandan newspaper to be living off raw food. Writers from Plutarch to colonial sailors of the nineteenth century made similar claims, but all have proved illusory, often colored by a racist tinge. “Only savages can be satisfied with the pure products of nature, eaten without seasoning and as nature provides them,” sniffed the entry in an eighteenth-century encyclopedia. In 1870 anthropologist Edward Tylor examined all such accounts and found no evidence of any being real. He concluded that cooking was practiced by every known human society. Similarly, all around the world are societies that tell of their ancestors having lived without fire. When anthropologist James Frazer examined reports of prehistoric firelessness, he found them equally full of fantasy, such as fire being brought by a cockatoo or being tamed after it was discovered in a woman’s genitals. The control of fire and the practice of cooking are human universals.
Still, in theory, societies could exist where cooked food is only a small part of the diet. The quirky nutritionist Howell thought so. In the 1940s he stated as part of his theory of the benefits of raw foods that the traditional Inuit (or Eskimo) diet was dominated by raw foods. His claim about the Inuit eating most of their food raw has been an important main-stay of the raw-foodist movement ever since.
But again it has proved exaggerated. The most detailed studies of un-Westernized Inuit diets were by Vilhjalmur Stefansson during a series of expeditions to the Copper Inuit beginning in 1906. Their diet was virtually plant-free, dominated by seal and caribou meat, supplemented by large salmonlike fish and occasional whale meat. Stefansson found that cooking was the nightly norm.
Every wife was expected to have a substantial meal ready for her husband when he got back from the hunt. In winter a husband came home at a predictably early time and would find the smell of boiling seal meat and steaming broth as soon as he entered the igloo. The long days of summer made the time of a husband’s return home less predictable, so wives often went to bed before he came back. Anthropologist Diamond Jenness accompanied Stefansson, and described what happened if a wife failed to leave cooked meat for her husband: “Woe betide the wife who keeps him waiting after a day spent in fishing or hunting! . . . Her husband will probably beat her, or stamp her in the snow, and may even end by throwing her household goods after her and bidding her begone forever from his house.”
Arctic cooking was difficult because of the shortage of fuel. In summer women made small twig fires, whereas in winter they cooked over burning seal oil or blubber in stone pots. After the snow had melted to water, the process of boiling meat took a further hour. Despite the difficulties, the meat was well cooked. “I have never seen Eskimo eat partly cooked meat so bloody as many steaks I have seen devoured in cities—when they cook, they usually cook well,” Stefansson wrote in 1910.