Authors: Chris Kresser
Tags: #Health & Fitness / Diet & Nutrition / Diets, #Health & Fitness / Diet & Nutrition / Weight Loss
I’ve helped hundreds of my patients and thousands of blog readers
and podcast listeners overcome chronic health problems using the knowledge and experience I gained over my own ten-year healing journey as well as in my formal education as a practitioner of integrative medicine. But there’s more work to be done. There are so many others out there still suffering from chronic illness or weight problems who haven’t been able to find help anywhere else. Maybe you’re one of them. If so, this book is for you. It will teach you how to heal yourself so your health won’t stand in the way of your fulfilling your dreams. The methods I share in this book have changed my life and the lives of thousands of others. It is my deepest wish that they will also change yours.
So let’s get started. In the next chapter, I’m going to give you a brief history lesson. (Don’t worry; there’s no pop quiz!) I’ll lay out the scientific argument that explains why you can live longer into the future by eating the way our ancestors did tens of thousands of years in the past.
Consider the following:
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Diabetes and obesity combined affect more than a billion people worldwide, including one hundred million Americans.
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More than half of Americans are overweight; a full third are clinically obese.
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Heart disease causes four out of every ten deaths in the United States.
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One-third of Americans have high blood pressure, which contributes to almost eight hundred thousand strokes every year—the leading cause of serious, long-term disability. Annually, there are 12.7 million strokes worldwide.
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More than thirty-six million people are now living with dementia.
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Depression is now the leading cause of disability, affecting more than 120 million people worldwide.
I could go on, but I think you get the point. We’re getting fatter and sicker every year.
Now imagine, for a moment, a world where:
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Modern, chronic diseases, like diabetes, obesity, some cancers, autoimmune disorders, and heart disease, are rare or nonexistent.
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The world population is naturally lean and fit.
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We all age gracefully with strong bones, sharp vision, and normal blood pressure.
While this might sound like pure fantasy today, anthropological evidence suggests that this is exactly how human beings lived for the vast majority of our species’ evolutionary history.
Today, most people accept disorders like obesity, diabetes, and heart disease as normal. But while these problems may be common now, they’re anything but normal. Our species evolved roughly two million years ago, and for more than sixty-six thousand generations, humans were free of the modern diseases that today kill millions of people each year and make countless others miserable. In fact, the world I asked you to imagine above was the natural state for humans’ history on this planet up until the agricultural revolution occurred, about eleven thousand years (366 generations) ago—less than 0.5 percent of the time recognizably human beings have been here. It’s a tiny blip on the evolutionary time scale.
What happened? What transformed healthy and vital people free of chronic diseases into sick, fat, and unhappy people?
In a word?
Mismatch.
Like it or not, we humans are animals. And like all animals, we have a species-appropriate diet and way of life.
When animals eat and live in accordance with the environment to which they’ve adapted, they thrive. Cats, with their sharp teeth and short intestinal tracts, evolved to be carnivores, so when we feed them grain-rich kibble, they develop kidney trouble and other woes. Cows
naturally graze on grass; when they eat too much grain, harmful bacteria proliferate and make them sick. We humans face a similar mismatch. Our biology and genes evolved in a particular environment. Then that environment changed far faster than humans could adapt, with a few important exceptions that I’ll cover later in this chapter. The result? The modern epidemic of chronic disease.
For the vast majority of existence, humans lived as Paleolithic hunter-gatherers, eating the meat they hunted, the fish they caught, and the vegetables, fruits, and tubers they picked while on the move. The agricultural revolution dramatically altered humans’ food supply and way of life. They learned to stay put, planting crops and domesticating cows, sheep, goats, and pigs. Early farmers consumed foods that their hunter-gatherer predecessors didn’t eat, such as cereal grains, milk and meat from domesticated animals, and legumes and other cultivated plants.
While scientists have argued that these developments allowed our species to flourish socially and intellectually, the consequences of this shift from a Paleolithic to an agricultural diet and lifestyle were disastrous for human health. In evolutionary terms, eleven thousand years is the blink of an eye, not nearly long enough for humans to completely adapt to this new way of eating. This is why the influential scientist and author Jared Diamond called agriculture “the worst mistake in human history.” He argued that hunter-gatherers “practiced the most successful and longest-lasting lifestyle in human history” and were all but guaranteed a healthy diet because of the diversity and nutrient density of the foods they consumed. Once humans switched diets and became more sedentary, our species’ naturally robust health began to decline.
How do we know that agriculture has been so harmful to humanity? There are three main points of evidence:
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A decline in health among hunter-gatherer populations that adopted agriculture
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The robust health of contemporary hunter-gatherers
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The poor health of people who rely heavily on grains as a staple
Let’s look at each of these in more detail.
Studying bones gives scientists a window into the health of our distant ancestors and offers insight into what an optimal human diet might be. Some archaeologists and anthropologists today may have a better understanding of human nutrition than the average health-care practitioner!
So what have these scientists learned from examining the bones of humans who shifted from a Paleolithic hunter-gatherer lifestyle to an agricultural one? The fossil record shows a rapid and clear decline in health in places where agriculture was adopted. Tooth decay and anemia due to iron deficiency became widespread, average bone density decreased, and infant mortality increased. These changes resulted in large part from the nutritional stress of eating a diet inappropriate for our species.
We also shrank. Skeletal remains from Greece and Turkey indicate that the average height of hunter-gatherers at the end of the ice age was five nine for men and five five for women. After agriculture was adopted in these areas, the average height fell to a low of five three for men and five feet for women. Archaeologists have found similar shrinkage in skeletons all over the world when populations shifted to agriculture.
Early farmers lost more than inches from their skeletons; they lost years from their lives. Anthropologist George Armelagos studied the American Indians living in the Ohio River Valley in approximately AD 1150. His team compared the skeletons of hunter-gatherers that lived in the same area with those of the early farmers who followed them. The farmers had 50 percent more tooth-enamel defects (suggestive of malnutrition), four times as much iron-deficiency anemia, three times more bone lesions, and an overall increase in degenerative conditions of the spine. Their life expectancy at birth also dropped, from twenty-six years to nineteen years.
In their book
The 10,000 Year Explosion,
anthropologists Gregory Cochran and Henry Harpending argued that these dramatic declines in health were brought on by a major shift in the human diet. When hunter-gatherers switched to farmers’ diets, their average carbohydrate intake shot up while the amount of protein plummeted. The quality of that
protein also decreased, since almost any type of meat has a desirable amino acid balance, whereas most plants do not. Vitamin shortages were common because the new diet was based on a limited set of crops and was lower in more nutrient-dense animal products. Evidence suggests that these early farmers, who depended on one or two starchy crops, like wheat or corn, may have developed vitamin-deficiency diseases such as beriberi, pellagra, rickets, and scurvy. Their hunter-gatherer ancestors, who ate a wide variety of foods rich in vitamins and minerals, rarely suffered from these diseases.
Because of “plentiful protein, vitamin D, and sunlight in early childhood,” our Paleo ancestors were “extremely tall,” had very good teeth, and larger skulls and pelvises, according to one group of archaeologists. Their farming descendants, by contrast, suffered skull deformities because of iron-deficiency anemia, had more tooth decay, were more prone to infectious diseases, and were much shorter, “apparently because subsistence by this time is characterized by a heavy emphasis on a few starchy food crops.” Farming may have offered our ancestors a more stable and predictable food supply, but this stability came at a great price.
A common question I hear from Paleo skeptics is something along the lines of “Didn’t Stone Age people die before their thirtieth birthday?”
It’s true that, on average, our Paleo ancestors died younger than we do. However, these averages don’t factor in challenges largely absent from modern American lives: high infant mortality, violence and accidents, infectious diseases, and lack of medical care. Hunter-gatherer populations had infant-mortality rates about thirty times higher than those in the United States today; early-childhood-mortality rates were more than one hundred times higher. These
higher infant-and childhood-mortality rates were caused by accidents, trauma, exposure to the elements, violence, warfare, and untreated acute infectious diseases—issues that, fortunately, few of us in the developed world face. These untimely deaths had the net effect of dragging down average life expectancy. If, out of ten Paleo people, three died in infancy, two died during childhood from exposure to the elements, and two died as teenagers in warfare, then even if the remaining three lived long, healthy lives, the average life span in this hypothetical group would still be short.
Recent research that has taken the high infant-mortality rates of our Paleolithic ancestors into account suggests that if our Stone Age forebears survived childhood, they had life spans roughly equivalent to those of people living in industrialized societies today, with a range from sixty-eight to seventy-eight years. Even more important, they reached these ages without any signs of the chronic inflammatory and degenerative diseases that we consider to be normal in developed countries, including obesity, type 2 diabetes, gout, hypertension, cardiovascular disease, and some cancers. Sure, those of us living in modern industrialized societies might live a little longer than hunter-gatherers, on average. But most of our elderly people now suffer from painful and debilitating diseases, take several medications a day, and have an unsatisfactory quality of life.
Fortunately, we don’t have to choose between eating like our ancestors and reaping the benefits of modern medicine. We can combine them to get the best of both worlds and enjoy long life spans without the degenerative diseases that are so common in the industrialized world.
Modern studies of contemporary hunter-gatherers—people who have had minimal exposure to industrial civilization and follow a traditional diet and lifestyle—suggest they are largely free of the chronic inflammatory diseases that have become epidemic in the industrialized world.
Anthropological and medical reports of these contemporary hunter-gatherers show they have far fewer modern illnesses, such as metabolic syndrome, cardiovascular disease, obesity, some cancers, and autoimmune disorders, than Westernized populations. In their study “The Western Diet and Lifestyle and Diseases of Civilization,” nutrition researcher Pedro Carrera-Bastos and his colleagues compared the health of traditional populations with the health of people living in industrialized societies. The contemporary hunter-gatherers were superior in every measure of health and physical fitness. They had:
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Lower blood pressure
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Excellent insulin sensitivity and lower fasting insulin levels (meaning they were less likely to develop type 2 diabetes)
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Lower fasting leptin levels (leptin is a hormone that regulates body fat)
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Lower body mass indexes and waist-to-height ratios (one way of measuring optimal weight)
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Greater maximum oxygen consumption (a measure of physical fitness)
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Better vision
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Stronger bones
Let’s look at some examples of contemporary hunter-gatherer populations around the world that, at least until a short time ago, followed the traditional diet and lifestyle.
Kitava is a small island in the Trobriand Islands archipelago in Papua New Guinea. Though not technically hunter-gatherers (they are horticulturalists), the Kitavans were, until recently, one of the last populations on earth still following a traditional diet similar in composition to Paleolithic diets. According to Dr. Staffan Lindeberg in his 1989 book
Food and Western Disease,
residents of Kitava subsisted “exclusively on root vegetables (yam, sweet potato, taro, tapioca), fruits (banana, papaya, pineapple, mango, guava, watermelon, pumpkin), vegetables, fish and coconuts.”
The Kitavans enjoyed excellent health. Dr. Lindeberg’s study of 2,300 Kitavans found that:
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None had ever experienced heart disease or a stroke (which was particularly remarkable because most Kitavans smoked, and smoking is one of the biggest risk factors for heart disease).
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They were very lean, with an average body mass index (BMI) of 20 in men and 18 in women. (By contrast, in 2010, the average BMI of Americans—both men and women—was 27, which is considered overweight and is only three points away from the obese category.)
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Compared to Westernized populations, Kitavans had very low levels of leptin and insulin, the hormones that regulate food intake and energy balance. Low levels of each are associated with leanness and overall metabolic health.
Most significant, Kitavans rarely suffered the diseases of aging that are so common in developed countries. Lindeberg noted, “The elderly residents of Kitava generally remain quite active up until the very end, when they begin to suffer fatigue for a few days and then die from what appears to be an infection or some type of rapid degeneration. Although this is seen in Western societies, it is relatively rare in elderly vital people. The quality of life among the oldest residents thus appeared to be good in the Trobriand Islands.”