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We Don’t Know What To Eat

Why can’t science solve our most basic question of survival?

Photo by Conrad Baker.

Growing up in Minnesota in the 1980s, my family’s kitchen was a scullery for healthy, common sense, midwestern eating. Children of a physician father and a nurse mother, my siblings and I were fed low-fat, low-salt, sensible portions of roast chicken and boiled potatoes, wild rice casserole, very well-cooked vegetables — and woefully deprived of fast food, Hostess snacks, and soft drinks (we called it ‘pop’).

And no butter for us; we ate margarine. Fleischmann’s margarine, to be precise. Every morning my dad would make a big stack of toast slathered with the stuff. And when I got home from school, I’d spread it on a stack of Carr’s table crackers as an after school snack. I’d guess we ate about a carton of margarine — 4 sticks — a week.

That carton was part of a massive amount of margarine consumed in the US. In 1983, Americans ate 2.3 billion pounds of margarine — twice as much as butter. We were all told it was better than butter — no saturated fats, no cholesterol. Much healthier.

It was all wrong.

Margarine of the day may not have had saturated fats, but it was packed with trans fats, an even more dangerous villain that packs the double whammy of raising LDL cholesterol (the bad stuff) and lowering HDL cholesterol (the good stuff). In the early 1990s, a wave of studies began to hint at the danger; trans fats were directly correlated with higher rates of heart disease and many cancers. A backlash ensued, and by 2006, the US required transfats labeling. In 2014 the Food and Drug Administration outlawed them altogether.

Today, we can’t believe how stupid we all were (except if you were in one of those cavalier families that stuck with butter all along).

The science over transfats marked a shift in the way Americans think about health and nutrition, and brought us into an era of regular contradictions and, often, confusion. Before transfats, a conventional wisdom emerged around nutrition and disease. Out of observational studies such as Framingham emerged an understanding that diets high in saturated fat and cholesterol and salt were associated with higher rates of high blood pressure and heart disease. The simple conclusion was to avoid foods high in these substances. In an era of square meals and four food groups, Americans tried to go along.

In the past 20 years, though, much of that conventional wisdom has gone out the window. Study after study found that things we thought were bad for us suddenly seem helpful, and seemingly benign foods — sugar, carbs, grains — are the new demons in the cupboard. The confusion has given rise to experts like Robert Lustig and Gary Taubes and — prince of all these — Michael Pollan, who promise to steer us through the chaos with their wisdom. But the science keeps on coming in contradictions. As much as you may be convinced you’ve found the truth, know that some amount of that truth is destined to be wrong, just as we were all wrong about margarine, and butter, and eggs, and fat, and salt, and on and on.

In many ways, it’s the simplest possible question: What should we eat?

But few questions have been so difficult question for science to answer with any certainty.

Vitamins, minerals, supplements, low gluten, low carbohydrates, low cholesterol — entire industries have been built on the inclusion and exclusion of certain substances in our diets. Avoiding disease is the general goal here; usually heart disease, with cancers a close second. But peer-reviewed science that connects these various inputs to specific outputs is surprisingly scarce.

Diets have been broadly linked with health for centuries, since Hippocrates apocryphally said “let food be thy medicine and medicine be thy food.” But only in the past century have verified associations between food and disease emerged. In recent years, science has linked various nutrition choices to arthritis, asthma, Alzheimer’s — and that’s just the A’s. These findings are largely statistical correlations, correlations borne out of observational studies.

The link between Alzheimer’s disease and Omega-3 acids, for instance, is largely a result of looking at populations with diets high in fish. Randomized control trials, considered the gold standard of research, have been less compelling. But in the popular imagination, the association has been processed into something much closer to outright cause and effect, complete with its own catchy diet — the MIND diet, short for Mediterranean-DASH Intervention for Neurodegenerative Delay diet (“DASH” being its own acronym from “Dietary Approaches to Stop Hypertension”). Of course there’s a book as well, offering an “eat this/not that” duality that appeals to our simple brains but is only modestly backed up by the science. We fall for these over simplifications because they cajole us into believing that science has solved the problem, that our industrialized food supply has hidden the true answer from us, that there is a pure diet — buried in history — that can indeed ward off disease and keep us forever healthy.

Except there’s not. If we wanted to go to a pure “original” diet akin to our early animal origins, it would be even more extreme than the paleo diet: all raw vegetables, occasional gorging on meat, and little or no processing of the food — no milling, no peeling, no blending, and most unsettling of all, no cooking. All we’d have is our teeth. In this raw form, we’d work harder to extract nutrients from our food — chewing and chewing and chewing — but we’d eat loads more fiber and far less sugar or starch. Of course such a diet likely sounds absurd, impossibly primitive. Without cooked food, we’d lose one of life’s great pleasures. Indeed, few things bring us more pleasure than food; it lights up our cortex like nothing else we consume on a daily basis.

This is why so few of us — less than two percent of Americans — choose to become vegetarians, despite ample evidence that a fully plant-based diet is our most effective, non-pharmacological tool to ward off diabetes, heart disease, stroke, and so many other diseases. It’s out there, with ample science to back it up. But going full vegan would require sacrifice beyond most of our capacity.

The pleasure we get from food, of course, is precisely why we consume so much bad stuff. Back when they were scarce, we craved sugar, fat and salt because our bodies needed them. Today, we’ve engineered a civilization exquisitely designed to serve us up that bad stuff in endless amounts (I’m looking at you, Ronald and Wendy and Colonel and Taco John). We may know it’s all bad for us, but we can’t help ourselves. Or we figure that one more scoop or slice won’t be so bad.

And it’s not just our biology, and the fast food industry, that is throwing contradictions at us. Food goes to the heart of the two landmines of human existence, religion and politics. There’s hardly a major faith that doesn’t stipulate what people should eat in one form or another, whether it avoiding certain meats or only eating fish on Fridays. Some religions even ask us to believe that certain foods are one in the same as God’s flesh. No wonder we’re confused.

Not to be outdone, politics have rendered food as controversial as climate change, and often closely related to it. At least six different agencies in the U.S. government are involved in food and nutrition — CDC, NIH, FDA, USDA, EPA, FTC — and each of these agencies is subject to various biases and influences, influences that have been visible in the USDA’s constantly shifting dietary guidelines from food groups to food pyramids and MyPlates.

What to eat according to the US Department of Agriculture, circa 2005.

The politics around food in the United States have made for several conspiracy theories — conspiracies which, alas, often turn out to be true, from how massive subsidies to Iowa corn farmers have created a glut of high fructose corn syrup to the corrupt corporate lobbying that influences those food pyramids. So much for expecting clarity and guidance from the government.

This, of course, is what science is for — to rationally cut through dogma and politics with empirical evidence.

Food surely seems like the sort of problem that science should be able to solve. After all, there are millions of test subjects and experiments going on every day. Why can’t we just measure what people do every day and run the numbers?

Because it turns out that science in humans is exceptionally messy. In other experiments in other organisms — rats, say— most every input can be controlled and calibrated, most every variable monitored and measured. Not so in homo sapiens, particularly with nutrition. A true controlled experiment — where people could be isolated and fed strict diets for years on end — is impossible. And when tracking humans in the wild, as much as nutrition scientists might try to isolate one input, sneaked snacks and unlogged calories can confound the results. Instead of randomized clinical trials, then, nutrition science often relies on observational or retrospective studies, where you start with a disease such as diabetes and try to work backwards to understand the causes and commonalities. Ultimately, the results of these studies can be suggestive, but almost never definitive.

The lack of definitive answers is especially frustrating because most of us know we’re doing it wrong. We’re eating too much or drinking too much and we see the problem, every day, in the mirror. But the solution — just how to change our diet for the better — continues to be elusive.

The answer, perhaps, may be staring back at us in those mirrors. Much of our health is ultimately a complex weaving of our diets upon our genetic lattice. This is why some people run marathons and never lose weight; it’s why others can eat horribly — like the guy who eats pizza every day — and still stay relatively healthy. Even more confounding that there may, in fact, be some microbial factor as well, such as the recent findings that some heart disease — long considered non-infectious and largely behavioral — may in fact have a significant bacterial component.

So it’s back to today’s conventional wisdom: Avoid processed foods. Eat more vegetables and less meat. And best to stop eating before you can’t eat another bite.

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