edible Garden outside bruce german’s office at UC Davis

Bruce German fixes dinner, part I


Rethinking nutrition

This is the first in a series of Medium posts. 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 I: The problem:

Why do we have so much trouble with nutrition? Our knowledge of nutrition fills libraries, and grows every year, and yet it remains incredibly difficult for people to lose weight, even when they are fully committed to the project. Cognitive behavioral therapy seems to work, but it’s unaffordable for most. Bariatric surgery is dangerous and expensive. The pharmaceuticals on the market don’t work very well and have troubling side effects. Why can’t we just put the science into practice and fix this? The answer to this question, according to Bruce German, a food chemist at University of California, Davis, is that our libraries full of nutrition data are miniscule compared to the gaps in our knowledge.

“What people are beginning to realize to their horror,” German told me, “is that we actually don’t know much about diet and health.”

German is a slight, energetic man of 61 years. He exudes a childlike enthusiasm for the mysteries he studies, and is given to gleefully expressing his scientific revelations in the most startling way possible (“I’d throw diet book writers in jail—every calorie restriction diet works, but it’s the last thing in the world that you should do.”)[1] When I visited he had a bad limp—an ice-hockey injury. He’s Canadian. There’s a big illustration of a hockey goalie above his desk and a wooden mountie holding up his iPhone charger. And though I didn’t see him use it, he had a Razor scooter in his office.

German has the rare ability to work on the tiniest details of science while still thinking creatively about how they might fit into grand overarching theories. He and his colleagues have hit upon an utterly new way of studying human nutrition, a method that might teach us once and for all how to eat, and which has already revealed that much of we thought we understood if flatly wrong.

For nearly two centuries nutrition scientists have been saying just the opposite: That we’ve figured out everything we need to know about nutrition. Michael Pollan has acidly etched this history of scientific arrogance in his book In Defense of Food, starting with Justus von Liebig who, in 1842, proposed that humans only needed potassium, phosphorus, and nitrogen to thrive—along with fat, protein, and carbohydrates. Liebig was obviously missing a few things (vitamins, for example), but no one knew that at the time and many doctors suggested that babies should be exclusively fed on Leibig’s formula—which, they presumed, was superior to breast milk.[2] It was assumed that Liebig had closed the book on nutrition.

In the 1950s, German said, conventional wisdom yet again held that scientists had solved the problem of diet. This overconfidence sprang from a decision to approach nutrition not as the study of foods, but as the study of their molecules. Going molecular was wonderfully enabling: Scientists were able to see what happened when they removed one chemical at a time from the kibble they were feeding to rats. If that nutrient was important, the animals would get sick. Methodically, researchers worked their way down the list of chemicals.

“In about 40 years, scientists were able to identify every single nutrient molecule that animals need to survive and reproduce,” German said. “There was the feeling that all the work was done. We assumed that all we needed to do was fortify the heck out of the food supply with essential nutrients. It was a great idea, but we will probably end up looking back at it as one of the greatest scientific goofs of all time.

The view at the molecular level fostered confidence by exposing the details of a small vista with perfect clarity—but it also left vast areas shrouded in darkness. The rapid accumulation of this sort of microscopic knowledge, German said, left three crippling assumptions embedded deep within nutrition science. First, the pinhole-focus on minutiae left the impression that the big picture, the food itself, was unimportant. Under this assumption, it shouldn’t matter whether sugars were latticed through a slice of bread or molded into a lollypop. Second, the cataloging of essential nutrients didn’t account for human diversity, and nutrition science treated everyone—Inuits, Bushmen, distance runners, and couch potatoes—as if they required the same diet. Third, given the focus on deficiencies, the best solution seemed to be the supplementation of nutrients to the national food supply. This final assumption had the consequence of putting large institutions, rather than individuals, in control of nutrition, because it was easy for governments and corporations to simply fortify salt, bread, and milk, with more than enough essential nutrients to everyone.

“We didn’t teach people what iodine is,” German said (it’s an element, commonly found in seawater and soil, necessary to make hormones in the thyroid). “We just iodized salt.”

As a result we are profoundly ignorant about diet and health. What little information did filter down into schools—like the food pyramid—was simplified to the point of nonsensicality.

These three assumptions—that molecules matter while the food itself is irrelevant, that everyone is the same, and that institutions rather than individuals should be trusted to control nutrition—are to a large extent responsible for the epidemics in heart disease, obesity, type 2 diabetes, and osteoporosis around the world, German said. More than a third of U.S. citizens are clinically obese. Demographers estimate that one of every three children who were born in the year 2000 will develop type 2 diabetes during their lives. Today’s children are expected to be the first generation in 200 years to die younger than their parents. It’s not an exaggeration to call this one of the greatest scientific errors (or goofs as German put it) of all time.

The problem with doing science that attempts to look, not just through the microscope, but also at the big picture, is that the work becomes exponentially more complex each time you zoom out. In a lab you can control variables so that only one element changes at a time: When you take all the salt out of the kibble and the rats sicken, it’s fairly safe to infer that they needed salt. If you’ve done the experiment carefully there shouldn’t be any other causes—no confounding factors, as they are known in science—to muddle the results. But if you want to ask how diet affects people’s health in a larger context, then you must wade through truckloads of confounding factors: Was it the fat that caused my (hypothetical) heart disease, or the sugar? Or could it be the fact that my grandmother passed me a susceptible gene, or that I didn’t exercise, or could it be because that my sleep was interrupted several times each night by police sirens? Nutrition research had been, all too often, focused on a field either so broad as to render the results nearly meaningless, or so specific that it was hard to find applicability outside the lab. The challenge for researchers was to find some new angle from which to study their subject, some new way of seeing that could break open the scientific logjam by providing microscopic accuracy and macroscopic applicability. That’s exactly what German did.

Part II: A better model for nutrition science


[1] The point is, in addition to fat, you lose muscle and bone mass, but what you gain back in the yo-yo is generally all fat.

[2] Liebig, though a brilliant chemist, wasn’t so good when it came to food: He also claimed that searing a piece of meat seals its juices inside, but this actually does just the opposite, drying and caramelizing the outer layer, and to this day cooks sacrifice steaks to Liebig’s confusion. Harold McGee has pointed out that you can achieve the same effect without drying out the meat by searing it at the end of the cooking process rather than the beginning.