This case emerges in intriguing detail in the work of Gary Taubes, a science writer and historian. We recommend his book Good Calories, Bad Calories, which is far more comprehensive and important than the diet-book title might suggest. It is an exhaustive summary and builds a broad case about cholesterol, fat, and carbohydrates, but the story is best summarized by an old, peer-reviewed joke that Taubes uses and we repeat here. A guy walking down the street one night notices a drunk hunched over in a determined search under a lamppost. “What are you looking for?” “I lost my car keys.” “Well, I’ll help you look. Are you sure you dropped them here?” “Nah. I dropped ’em over there a ways, but the light’s better over here.”
The light that has focused our search on this matter for a couple of generations is the fact that doctors can easily measure cholesterol—which is one of hundreds of biochemicals vital to our system and yet somehow the one believed to reveal everything there is to know about heart disease. Cholesterol is technically a chemical form called a “lipid,” a category that includes fats, but cholesterol itself is a sterol. It is nonetheless essential to every single cell in your body. But when we talk about cholesterol, we generally talk about lipoproteins, which are specialized structures the body makes to transport fats (including cholesterol) and proteins in the bloodstream. There are a variety of lipoproteins, and cholesterol is contained and freighted in each. There is no good way to measure cholesterol itself, so we measure lipoproteins as a proxy.
The first cut of classification gives us low-density lipoproteins (LDL) and high-density lipoproteins (HDL), the “bad” and “good” cholesterol, respectively. Those two and a third, triglycerides, make up the three common numbers of the garden-variety lipid profile. The focus is mostly on LDL, the so-called bad cholesterol. But not so fast. LDL itself subdivides into two distinct structures, according to size, and only the very small ones are thought to lead to damage. When your doctor uses your lipid profile to prescribe a lifetime of statin drugs and possibly a lifetime of the muscle cramping that is the known side effect, she often hasn’t a clue which type of LDL particles dominate in your profile, despite evidence that says only one of these is associated with heart disease. Further, we have known about the two sizes of particles and their relative importance since cholesterol was first discovered early in the twentieth century, but mostly we ignore the distinction.
And further still, there is plenty of evidence that says heart disease is better predicted by triglyceride levels, and this number ramps up according to how much sugar you eat, not fat. And even further, a lipid profile that shows high triglycerides and low HDL is neatly predictive of the bad kind of LDL. This profile, and not high cholesterol or even high LDL, is far more strongly associated with heart disease.
The whole issue has become layered in misinformation and mythologies. For instance, there is the widespread belief that eating foods high in cholesterol will yield elevated cholesterol in your bloodstream. This is a straightforward enough assumption, but it’s probably wrong. Taubes reviewed the evidence through the years and concluded, “Dietary cholesterol, for instance, has an insignificant effect on blood cholesterol. It might elevate cholesterol levels in a small percentage of highly sensitive individuals, but for most of us, it’s clinically meaningless.”
At the same time, a diet high in carbohydrates is strongly associated with high triglycerides, low HDL, and the damaging particles of LDL, which is the killer profile. And none of this is new, although it has been borne out by new studies. Even before Keys began his mission, there was plenty of evidence to contradict his views. A whole generation of nutritionists have rested arguments on Keys’s famous Seven Countries Study, a piece of work he said proved his hypothesis about the connection between dietary fat and heart disease. The problem is, Keys analyzed data from twenty-two countries and deliberately assembled a list of the first seven that made his point and ignored the longer list of countries that contradicted it.
The irony here is that the misguided attack on all fats and cholesterol targeted high-cholesterol foods like eggs and butter and argued that we would be better off eating highly processed substitutes like Egg Beaters and margarine. Which brings us to the fats, and the refinement of the argument about fats. Those substitutes had in common a type of fat that is manufactured and has no precedent in evolutionary history: what we call “trans fats,” which is a truncation of their technical chemical name, trans-isomer fatty acids. These are also labeled “unsaturated fats,” but the better way to think of them is as not existing in nature. These are the fats that harm you, and together with sugar they are the foundation of the industrial foods system.
The damage began with Crisco. Procter & Gamble used a process called hydrogenization—a way to turn oils into solid fats—to invent and introduce Crisco, billed as a lard substitute, in 1911. The same process has since spawned a string of fat substitutes, all based in vegetable oil—especially oil that derives from processing corn and soybeans. It was, for the food industry, a way to spin what was then a waste product of our farm surplus production into a marketable product, and marketing was the key. The early campaigns to sell the public on shortening and margarine were the prototypes for today’s sea of hype and cynicism that is the processed foods system. These are the roots of fast food.
The problem with trans fats is that hydrogenation created a set of fatty acid molecules unprecedented in our digestive systems. We are not evolved to handle them. As often as not, foreign molecules in the body rightly trigger an immune response, including inflammation. Inflammation, in turn, is every bit as important as, if not more important than, cholesterol in the genesis of arteriosclerosis and the resulting heart disease. That is, there is a pretty direct and logical link between heart disease and the margarine once marketed as the heart-healthy substitute for butter. By the 1950s, nutritionists were beginning to suspect that link. Epidemiologists now estimate that every 2 percent increase in consumption of trans fats increases the collective risk of heart disease by 23 percent. The National Academy of Sciences says that no level of trans fats in our food is safe. None. Because they are so tied up with heart disease, this, of course, strikes straight at the core of one of our most important diseases of civilization—but there are also linkages here that one might not expect. For instance, a study in 2011 showed that eating trans fats greatly increases the risk of clinical depression, which—as you will recall—is identified as a rapidly growing problem worldwide and, we argue, a disease of civilization.
In the case of trans fats, a measured dose of fat-o-phobia may well be in order, and one should avoid them like the plague. Unfortunately, the bad advice on other fats that began with Ancel Keys tarred some of our healthiest foods with the same brush, and this needs to be corrected, especially in the case of omega-3s. That’s a term you have heard and may well have heard in nutritional advice like this. Step one: Avoid fats. Step two: Be sure to get a good supply of omega-3s. This is not so much advice as it is a hangover of fat-o-phobia. Omega-3s are fats—fats that are in critically short supply in our diets. This shortage may well be a factor in widespread depression but also in high cholesterol, heart disease, inflammation, and compromised brain development.
The clue to the importance of all of this is the name of the category that includes omega-3s, which is essential fatty acids. They are labeled “essential” because without them we could not survive. Literally. We get omega-3s from a variety of sources, but mostly from free-range meats, especially cold-water fish. Vegetarians get them from the few plant sources that contain them, such as walnuts or flax oil.
Their counterparts are omega-6 fats, also present in meat, and although omega-6s are seeing some bad press lately, they are also essential fatty acids. The problem is one of balance—and again, this is rooted in our industrial system of agriculture. Cows evolved to eat grass, but mostly we no longer feed them grass; we feed them the corn and soybeans that are the prime products of our industrial agriculture system. The practice creates beef high i
n omega-6 fats and low in omega-3s. The practice of fattening beef in feedlots and the preponderance of factory beef in the fast-food system passes this omega-3 shortage into our bodies.
But this is also why eating red meat itself has gotten a bad rap, with endless strings of studies linking it to heart disease and a variety of other issues. The beef that is the basis of these conclusions is factory beef, and no wonder.
Meanwhile, the shortage of omega-3s undoubtedly shows up in areas we might not suspect, and one example from the literature demonstrates just how far-reaching this effect might be. One researcher in education—not in nutrition—performed a meta-analysis of all peer-reviewed research on proven methods to increase a child’s intelligence (that is, boost academic performance). The conclusion: “Supplementing infants with long-chain polyunsaturated fatty acids [specifically omega-3s], enrolling children in early educational interventions, reading to children in an interactive manner, and sending children to preschool all raise the intelligence of young children.”
(We think there is enough evidence to add exercise to the list, but the point stands.)
And it is a problem that can be easily solved by eating grass-finished beef, now widely available thanks to increased awareness and demand, but also wild-caught fish, free-range eggs, and even walnuts. This is a corrective to generations’ worth of bad assumptions about fats. And yes, our bloodstreams are full of fat as a result of the industrial diet and processed food, but this is not all fat’s fault. Remember the insulin response and the insulin resistance generated by excess carbohydrate consumption. Remember that insulin immediately shuts off the body’s use of fat; it sends signals to keep it in storage and at the same time signals muscles to cease burning fat and start burning glucose. This alone goes a long way toward explaining why fatty acids jam up in our bloodstream, especially as triglycerides. It’s not because we are eating fats; people always have. It is because excessive carbohydrates, especially sugar, are preventing us from burning them. Cut out the carbs, and the fat problem takes care of itself, as long as you eat the right kinds of fats.
But in his book, Taubes takes on this issue from another direction, a convincing capstone of an argument. There is no doubt that obesity is increasing in a number of countries around the world. In the United States, we can plot that increase on a graph over the last fifty or so years. And we can plot, alongside that, three other graphs, for per capita consumption of protein, fats, and carbohydrates (including sugars). The first two graphs show flat lines with no real increase in per capita consumption of either protein or fats. In sharp distinction, per capita consumption of carbohydrates in the United States has risen steadily in marked and obvious parallel to obesity.
This is not a new trend. Annual per capita sugar consumption in the United States was 5 pounds per person in 1700, 23 pounds in 1800, 70 pounds in 1900, and 152 pounds today. This is why we talk about sugar when we begin talking about what ails us. Want to go wild? Here’s how. Don’t eat sugar, not in any form. Not sucrose, not pure cane sugar, not high-fructose corn syrup, not honey, not in all those other polysyllabic chemical names that reveal industrial processes rooted in corn: maltodextrin, dextrose, sorbitol, mannitol. Not apple juice. John thinks this is one of the hidden causes of childhood obesity, even in households where there is very good parenting.
Don’t eat dense packages of carbohydrates, particularly refined flour. No bread, no pasta, no bagels, certainly no cookies. No grain, period, not even whole grain. Don’t eat trans fats. Period. And you may have figured out the derivative rule by now. Trans fats and sugars are the foundation of processed food. Do not eat processed food.
You will notice that in this prescription, we have remained silent on the topic of dairy products, and not because the topic is irrelevant. Dairy is, in fact, interesting both for what it tells us about evolution and also in the ways it resonates through your health and well-being.
To begin with, dairy is one of the more outstanding—if not the outstanding—exceptions to the rule that the basic human design has not changed in fifty thousand years. The fact is, about a third of humanity has evolved the ability to digest lactose, the sugar in milk, as adults. All children make the enzyme lactase (the gene product that digests lactose) for the obvious reason that baby mammals have to digest milk to survive. But in deep evolutionary time, all adults lost that ability as we matured, which was not a problem in our ancestral homeland in Africa, near the equator, with ample sunlight. But as humans migrated north, winters brought shorter days, less sun, and a vitamin D deficiency, which was a serious problem. (And as we shall see, it still is a serious problem.) We get vitamin D from the sun, but also from milk.
In evolution, necessity does indeed mother invention, and it was in Eurasia that a mutation occurred that allowed adults to digest lactose. To this day, that ability tracks in populations with roots in Eurasia, the third of us who can tolerate lactose into adulthood.
But interestingly, there was a parallel step in cultural, not biological, evolution that solved the same problem. Around the Mediterranean and on the Asian steppes, there is widespread lactose intolerance in the populations, yet these people eat dairy products like cheeses and yogurt and have for a very long time. They have adopted a cultural practice that outsources the job of digesting lactose: fermentation. Fermentation uses bacteria to digest lactose, meaning that people with lactose intolerance can still get nutrition and vitamin D from fermented dairy products. They are using an external microbiome, an ingenious bit of outsourcing.
We have remained silent on dairy in our prescription because this evolutionary history outlines some individual solutions. Do what works for you.
WHY VARIETY
Close readers will notice by now that our argument appears to have painted us into a corner, and it is precisely the same predicament that traps most diet nags, an argument that we become ill and fat by eating this or that food. Because we are not just talking about quantity here; we are talking about restricting a whole class of foods, and humanity’s most important foods at that. This contention runs smack up against the evolutionary foundation of humanity that we laid out in the beginning: we humans are the ultimate generalists, the Swiss Army knives of not just movement but nutrition, too. The foundation of our success as a species is our ability to adapt to a wide range of conditions, environments, and foods—the very ability that allowed us to occupy the entire planet, unlike any other species. In fact, we are not going to shy away from this apparent contradiction. Not only did evolution equip us so we can eat a wide variety of foods, but it made variety a necessary condition of our well-being. We not only can but must have variety to be healthy. Remember, this was George Armelagos’s second and more important rule, a fact so often missed in books that attempt to adapt evolutionary understanding to prescriptions.
“I think variety is the key to all of it,” he says.
Even our argument that you should not eat sugar does not violate this rule; restricting sugar enables the body’s responses that support variety. Remember homeostasis, the complex array of thermostats that allow our bodies to roll with the punches? Homeostasis underscores much of what we have to say. These thermostats let us weather variation and return to a sustainable state. Insulin’s response to sugar in the bloodstream is homeostasis at work. But insulin resistance is the signal that we have swamped that system, so much so that our internal thermostats cease to function and therefore cease to enable us to navigate the world of diversity and variety.
This is the negative side of the argument, and the positive side is more intriguing still. The enormous energetic demands of our brains mean, as we have seen, that we could not be at all casual about nutrition. The demand for energetically dense foods dictated that we eat meat, which meant hunting, which in turn required a great deal of intelligence. But it also meant gathering plants, which in turn required detailed knowledge of plants, seasons, and even subtle clues like what sort of leaf pattern in what sort of state of wilt signaled that a succulen
t tuber was hidden a few feet under the ground, ready for harvest. Our attention to color, our empathy for animals, our recognition of patterns, even our ability to communicate with one another—all are rooted in this fundamental need to feed our brains, and at the same time, our brains return the favor by allowing it all, a sort of positive feedback loop that drives development. We revel in all of this and take pleasure in it, still enjoying a primal rush of pleasure on walking through a bustling farmer’s market on a sunny afternoon.
But the whole array of demands gets ratcheted up to another level still when we add to this what has come to be called the omnivore’s dilemma, a dilemma caused by conflicting interests. Because we are omnivores and because we range over the entire planet, it is in our interests to exploit as many food sources as possible. This means that an important characteristic of omnivores is bred to the bone in humans: we are neophiliacs. We have to be. We have an innate love of novelty, of variety, a need to sample new things. And at the same time, some of those bright and shiny new things, some of those foods on offer in the wild, are poisonous—a lot more than you might think. Not acutely so, like sugar, but lethal poisons that drop you dead on the spot. Thus, it is equally in our interests to be neophobes, to fear new things, thereby causing a conflict at the center of the human condition.
Throughout the course of our evolutionary history, we have negotiated this dilemma with cuisine, sharing cultural information about what is good to eat and not good to eat. We depend on others—elders, mothers, and fathers—to hold this information specific to place and teach it to those who need it. It is the very essence of culture, one more way in which we depend on one another for survival. And there is nothing perfect about this solution; if it were perfect, a given culture long adapted to a given place would make use of all the nutritious plants and animals and leave all the poisonous ones alone. Not the case. For instance, in one of his papers on this topic, Armelagos reports that the !Kung people of the Kalahari Desert eat a total of 105 species of plants and 260 species of animals from the desert savanna environment—a total of 365 species of plants and animals. But modern biologists have determined that the same place holds at least 500 edible species. The gap is a measure of the cultural negotiation of the omnivore’s dilemma on the safe side. Still, the undeniable push in humanity is toward variety.
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