Authors: Chris Kresser
Tags: #Health & Fitness / Diet & Nutrition / Diets, #Health & Fitness / Diet & Nutrition / Weight Loss
A long, healthy life followed by an easy, quick death. Don’t we all want that?
The Inuit are a group of hunter-gatherers who live in the Arctic regions of Alaska, Canada, and Greenland. They eat primarily fish, seals, whale, caribou, walrus, birds, and eggs: a diet very high in fat and protein, with very few vegetables or fruits. They live in a harsh environment that is marginal at best for human habitation. Yet early explorers, physicians, and scientists unanimously reported that the Inuit they encountered enjoyed excellent health and vitality.
Dr. John Simpson studied the Inuit in the mid-1850s. He noted that the Inuit were “robust, muscular and active, inclining rather to spareness, rather than corpulence, presenting a markedly healthy appearance. The expression of the countenance is one of habitual good humor. The physical constitution of both sexes is strong.” This is especially remarkable considering the inhospitable environment the Inuit lived in, and it’s a testament to the nutrient density of the animal foods that made up the majority of their diet.
Nearly a hundred years later, an American dentist named Weston A. Price noticed an alarming increase in tooth decay and other problems in his patients, and he set out to determine whether traditional peoples who had not adopted a Western diet suffered from the same problems. In 1933, he took a trip to the Arctic to visit the Inuit, one of many cultures he studied, and he was deeply impressed by what he found. He praised the Inuit’s “magnificent dental development” and “freedom from dental caries” (that is, they had no cavities).
It’s especially impressive that the Inuit enjoyed such robust good health when you consider that their diets were 80 to 85 percent fat, a percentage that would surely horrify the American Medical Association!
Aboriginal Australians, or Indigenous Australians, were the original inhabitants of the Australian continent and surrounding islands. They traditionally lived as hunter-gatherers, consuming mostly animal products—including land mammals, birds, reptiles, sea creatures, and insects—along with a variety of plants. The quality of their diet depended in large part on where they lived: the subtropical, coastal areas were lush and provided abundant food; the harsh desert interior offered less in terms of both diversity and amounts of food.
Nevertheless, numerous studies suggest that even those Aboriginal Australians living in marginal environments were free of modern diseases like obesity, diabetes, and heart disease. Weston Price described them as “a living museum preserved from the dawn of animal life on the earth.”
Even today, contemporary Aboriginal Australians who maintain a traditional lifestyle are lean and fit and show no evidence of obesity, insulin resistance, type 2 diabetes, or cardiovascular disease. A study published in 1991 found that this population had optimal blood pressure, fasting-glucose levels (high levels indicate diabetes), and cholesterol levels, with an average body mass index well below that of Australians living in urban environments.
Aboriginal Australians who make the transition from their traditional hunter-gatherer lifestyle to a Westernized lifestyle develop unusually high rates of diabetes, cardiovascular disease, and obesity, according to the same study, and Westernized Aboriginal Australians experience a dramatic improvement in metabolic and cardiovascular health when they return to their traditional ways.
These three groups of hunter-gatherers have enjoyed good health with their traditional lifestyles into the twenty-first century, although each eats a very different diet. This may indicate that what we don’t eat might be just as important as what we do.
Another way to evaluate whether traditional Paleolithic diets are healthier than modern diets is to look at cultures and groups that consume large amounts of grains. Are they more likely to have health problems? There’s a great deal of research that says yes. Whole grains, legumes, nuts, and seeds contain compounds called phytates that bind to minerals such as calcium, iron, zinc, and manganese, making them more difficult to absorb. If a food contains nutrients that you can’t absorb, you’re not going to reap their benefits.
Studies show that children on vegetarian macrobiotic diets—“healthy” diets composed of whole grains (especially brown rice), legumes, vegetables, and some fruits—are deficient in vitamins and minerals and are more likely to develop rickets than their meat-eating peers. Breast-fed babies of macrobiotic mothers may be getting lower levels of vitamin B
12
, calcium, and magnesium, according to some research, which may result in these babies having delayed physical and cognitive growth.
Cultures that are heavily dependent on grains often show signs of severe vitamin A and protein deficiencies, which make them more susceptible to infectious diseases. Dr. Edward Mellanby, the discoverer of vitamin D, compared the agricultural Kikuyu tribe with the pastoralist (livestock-raising) Masai tribe, who consume primarily the milk, blood, and flesh of the cows they raise. Dr. Mellanby discovered that the Kikuyu, who lived mainly on cereals, had a far higher incidence of bronchitis, pneumonia, tropical ulcers, and tuberculosis.
We’ve been raised to believe that healthy whole grains are nutritional marvels, but cereal grains like corn, wheat, and rice don’t deserve the label
healthy.
They’re inferior to animal products as a source of protein because they’re incomplete, meaning that they are missing one or more essential amino acids. (Essential amino acids are those that we can’t synthesize and therefore have to get from our diets.) They’re also lower in vitamins and minerals compared to meat and the variety of wild fruits and vegetables consumed by our ancestors.
The evidence suggests that when we eat grains at the expense of more nutritious foods—especially when those grains are not properly prepared to reduce phytates and toxins—our health suffers.
Eating meat and cooking food is quite literally what made us human. The transition from a raw, exclusively plant-based diet to one that included meat and cooked food (as well as starchy tubers) is what enabled the brains of our pre-human ancestors to grow so rapidly.
Humans have exceptionally large, neuron-rich brains relative to body size compared to nonhuman primates. For example, gorillas have bodies that are three times larger than ours, but they have smaller brains with only about a third the number of neurons that we have. So why is it that the largest primates don’t also have the largest brains?
The answer is that the brain competes with other organs for resources in the body. Gorillas require a large, metabolically expensive digestive tract to process the high-fiber, low-calorie plant matter they consume. This doesn’t leave enough resources for larger, higher-performance brains (like ours). The human brain is an expensive metabolic tissue: it consumes 20 percent of total body energy even though it represents only 2 percent of body mass.
The larger you are, the more you need to eat. The more you need to eat, the more time you have to spend feeding yourself. Gorillas, who are vegetarians, already spend as much as 9.6 hours of a twelve-hour day eating, in part because the fibrous plant matter they consume takes so long for their bodies to break down and absorb. In order to provide enough energy for a human-like brain, a gorilla would have to eat for an extra two hours a day! Likewise, early humans eating only raw vegetation would have needed to eat for more than nine hours a day to get enough calories to support their large brains.
Gathering food was both dangerous and time-consuming, so it is unlikely that our ancestors had a completely vegetarian raw diet. When they cooked their meat, it became easier for them to chew and therefore to digest and absorb, which increased both the calories available and the nutritional density of their diet.
As you’ll see in
chapter 3
(which focuses on nutrient density), meat provides an ideal mix of amino acids, fats, and vitamins and minerals for brain growth and maintenance. Vitamin B
12
—available only in animal foods—is particularly important for developing brains.
It’s possible to survive on these vegan or vegetarian diets today, but they’re far from optimal or normal for our species. People choose not to eat meat for many reasons, including concerns about the ethical treatment of animals, the amount of resources depleted in raising animals for consumption, and religious beliefs. Those are complex issues beyond the scope of this book. My point is simply that we may not have become the humans we are without this nutritious food source.
The agricultural revolution began humans’ transition away from sixty-six thousand generations of good health. But this shift wasn’t really complete until about six generations ago, when humans reached another milestone: the Industrial Revolution, which ushered in a new age of mass production, transportation, urbanization, and economic development.
Although the beginning of the Industrial Revolution dates back to the eighteenth century, its dietary effects didn’t become evident until the late 1800s. Improved transportation meant greater access to food for more people. Mass-production methods meant that items like white flour, table sugar, vegetable oil, dairy products, and alcohol could become fixtures at every table. White flour, for example, became widespread in the United States after 1850, but it didn’t reach the saturation point until the 1890s. People living in England in the mid-Victorian period, between 1850 and 1890, generally enjoyed great health and still ate a fairly preindustrial diet. With falling prices and improved transportation, however, by around 1900, modern foods made up about 70 percent of the total calories the average person consumed each day—a remarkable change when you consider that none of them was available for the vast majority of human history.
Another significant change that came with the Industrial Revolution was a decrease in the diversity of the human diet around the world. Paleolithic hunter-gatherers consumed a large variety of plant species, primarily fruits, tubers, and vegetables, as do their modern counterparts. (For example, the Alyawarra tribe in Central Australia consume ninety-two different plant species, and the Tlokwa tribe in Botswana a hundred and twenty-six.) Thanks to improved railways, roads, and canals, a limited number of crops could be grown and shipped cheaply to every corner of the planet. Today, 80 percent of the world’s population lives on only
four
principal staple plants: wheat, rice, corn, and potatoes.
The food introduced on a large scale by the Industrial Revolution (and grown with newly invented pesticides containing toxins) may be cheaper for us, but it isn’t better. A hundred grams of sweet potato (about
half a potato) contains only about 90 calories, and a hundred grams (one small serving) of wild-game meat contains about 150 calories, but both of these foods contain a wide spectrum of beneficial micronutrients. By contrast, a hundred grams (less than a cup) of refined wheat flour contains 361 calories, the same amount of sugar contains 387 calories, and both have virtually no beneficial nutrients. A hundred grams of corn oil (about seven tablespoons), a staple of modern diets, contains a whopping 881 calories and has essentially no nutritional value.
Even worse, industrialization completely changed the way humans lived. In 1800, 90 to 95 percent of Americans lived in rural areas or in small villages. In 1900, about half the population resided in nonurban environments. Today, less than 16 percent of all Americans live in rural areas. People who moved to cities to work became more sedentary. Longer work hours meant less time in the sun and less sleep. Stress—chronic, unrelenting—became a fixture in everyday life. While the Industrial Revolution undoubtedly improved human health in many ways (e.g., greater protection against infectious disease and better emergency medical care), these benefits did not come without significant cost. We have the Industrial Revolution to thank for new diseases of civilization that were rare or virtually nonexistent in preindustrial cultures:
•
In the early 1950s in Uganda, only 0.7 percent of people above the age of forty showed evidence of having had heart attacks, according to an autopsy study. Today in Uganda, a country where the Western-style diet has taken hold, heart disease is the fourth-leading cause of death.
•
In Papua New Guinea, heart attacks were unknown prior to urbanization. Today, the rate of heart attacks is skyrocketing, with upward of 400,000 heart attacks a year in a population of 5.4 million people.
•
Among the Pima Indians in Arizona, the first confirmed case of diabetes was reported in 1908. Thirty years later, there were twenty-one cases, and by 1967, the number had risen to five hundred. Today, half of all adult Pima Indians have diabetes.
•
When some of the South Pacific people of Tokelau migrated to nearby New Zealand and switched to a Western diet, they developed diabetes at three times the rate of those who had remained in Tokelau.
As study after study shows, the more Westernized a traditional culture becomes, the more disease it experiences. Today obesity, diabetes, heart disease, and other chronic degenerative conditions affect well over a billion people worldwide and kill millions of people each year. It may be nearly impossible for you to imagine life without these disorders. Yet they’ve been common for only the past two hundred or so years, a tiny fraction of the time humans have existed on the planet.
I’ve argued that humans are mismatched with an agricultural diet because the environment changed faster than our species’ genes and biology could adapt. But this doesn’t mean that we haven’t developed
any
adaptations to agriculture or that human evolution stopped in the Paleolithic era.
In fact, the pace of genetic change in humans has actually increased during the past few thousand years. Evolutionary biologist Scott Williamson suggests that evolution is occurring one hundred times faster than its previous average over the six million years of hominid evolution and that as much as 10 percent of the genome shows evidence of recent evolution in European Americans, African Americans, and Chinese.