This is the forth in a series of Medium posts. They start here. Excerpted from All Natural: A Skeptic's Quest to Discover If the Natural Approach to Diet, Childbirth, Healing, and the Environment Really Keeps Us Healthier and Happier, from Rodale, which comes out January 29th.
Part IV: Human variety
Assumption 2: Everyone is the same
There’s a page from Sports Illustrated magazine that German sometimes uses in lectures with photographs of Olympic athletes in their underwear: some bulge like comic book characters; some are planed down to willowy smoothness; some are birdlike, gracile; some hulk as if they’d been wrapped for shipping. It’s ridiculous to suggest that each of these people would be better off eating the same diet. And yet for years the nutritionists have advised just that.
Mother’s milk, on the other hand, is personalized for each infant. It contains antibodies specialized to protect against local germs. Its balance of fats and sugars shifts depending on the baby’s size, hunger, and energy expenditure. When a baby is more active and burning more calories, its movements—butting and jiggling the breast—causes the fat content of the milk to increase. And—at least among rhesus macaques, which produce milk similar human milk—the breast produces different mix of nutrients depending on whether the baby is male or female (the boys get fattier milk, while the girls get a greater volume of thinner milk—the upshot is that males feed less frequently and explore more, while females feed more often and perhaps learn more from their mothers). Milk changes continuously, providing age-appropriate levels of nutrients for different stages of development.
The major components of milk, however, remain the same, even as their amounts shift relative to one another. The way that fats are assembled, in particular, are consistent. “The most well-conserved gene set across all mammals is the set that creates fats in milk,” German told me. “It’s one of the great treasures in the genome.” This is interesting because it hints at further overconfidence when the nutritional witch hunt turned to fats. The bulk of the fats in breast milk are saturated, which are suspect under the nutritional orthodoxy because they are associated with cholesterol. If breast milk were sold in grocery stores, it would be considered a dangerously high-cholesterol food. Yet researchers found that cholesterol levels in breast milk couldn’t be budged by putting mothers on diets. Scientists also noticed that the more cholesterol neonates drank in their milk, the less they produced in their livers, which led to the hypothesis that mothers were programming their babies—tuning their bodies to produce no more and no less cholesterol than they uniquely needed. This discovery contributed to science showing that people can have high cholesterol for different reasons: Some are eating too much of it, some are producing too much, and some aren’t efficiently eliminating it from the bloodstream. The study of milk, in other words, has suggested that the meaning of “high cholesterol” depends utterly on context.
“The thing that bothers me most about the industrial, authoritarian model of nutrition,” German said, “is that it is in diametric opposition with human evolution.”
Homo sapiens has evolved a remarkable elasticity when it comes to diet: We have both shearing teeth and grinding molars, and our digestive system is that of a generalist. If you look deeper, beyond the tissue and bone, it becomes clear that the human genome contains multitudes: Most people in the world—aside from those with ancestors from the Eurasian cow belt, and a few cattle-rich spots in Africa—lack the genetic mutation required to digest dairy after infancy. Similarly, descendants of grain-growing cultures have genetics to manufacture more salivary amylase—an enzyme that breaks down starches—than hunter-gatherers. Furthermore, people routinely overcome these genetic predispositions, recruiting gut bacteria to help them digest lactose, for instance.
“We are at the platinum level of freedom,” German continued, “and yet nutritional dogma says we are all supposed to eat the same way?”
Humans have been molded to eat diets as diverse as humanity itself. To cater to the wondrous diversity of humankind, German thinks that nutrition science must follow the example of milk, and tailor recommendations for each individual. Which brings us to his third point.
 It’s possible to zero in on these issues by looking at different molecules in the blood: one (phytosterol) can show you are taking too much cholesterol in, another (mevalonate) can reveal if your liver is the problem, and a third (7-α-hydroxy-4-cholesten-3-one) can indicate that you aren’t eliminating enough cholesterol by converting it to bile. Each condition demands a different treatment. But these tests aren’t routinely performed before doctors make a prescription to control cholesterol.
Excerpted from All Natural: A Skeptic's Quest to Discover If the Natural Approach to Diet, Childbirth, Healing, and the Environment Really Keeps Us Healthier and Happier, from Rodale, which comes out January 29th.