Many years ago I was walking along Kilburn High Road with a sharp-eyed naturalist friend when he spotted an ear of domestic wheat growing in one of those squares of soil cut into the pavement for urban trees—forlorn scraps of earth that litter gets stuck in, cigarettes get put out in, and dogs (and the occasional drunk) like to defecate in. He practically whooped with joy, then spent a good five minutes crouched over it—much to the confusion of passers-by—while he lectured me, excitedly and at length, on the marvel of wheat and the natural history of our relationship with it. It was the first time I had ever really thought about just how dependent we are on a species of grass that was probably first domesticated over ten thousand years ago in what is now Turkey. For most of us urban dwellers, felt knowledge of our dependence on domesticated grass is rare, as rare as, well, finding an ear of wheat growing on Kilburn High Road.

The energy we eat as food comes from the sun. As we are unable to make use of the sun’s energy directly, we have to consume it via substitutes. Green plants such as grass—and their marine equivalents, phytoplankton—can draw energy directly from the sun which they use to synthesise water and carbon dioxide to produce sugars, a process called carbon fixing. It is this ability to draw on the sun’s energy that puts plants and phytoplankton on the first rung of the food chain. Although human beings have traditionally eaten the seeds of grass in the form of breads, pastas, and pastry, it is also a primary source of food for livestock. Our dairy produce, our beef cattle, and our poultry are all fed to a greater or lesser extent on domesticated grasses. As Michael Pollan points out in his book The Omnivore’s Dilemma, the Biblical phrase “we are as grass” is more than just a comment on our brevity and insignificance: it is, or at least has been for large numbers of us, almost literally true.

According to Pollan, what should be a straightforward relationship with food, going back, via brief steps to the grasses that fix the sun’s energy, has become a source of grave pathologies. America—and much of the world is following in its footsteps—has replaced simple, local food chains with what he calls a “military-industrial food complex,” a behemoth of almost inconceivable magnitude and complexity. Add to this the lack of a stable American food culture—a product, for Pollan of America’s migrant origins—and the conditions are ripe for what he calls America’s “national eating disorder:”  how did we ever get to a point where we need investigative journalists to tell us where our food comes from and nutritionists to determine the dinner menu.

Paradoxically, at the heart of all this complexity lies a single foodstuff, a single mutant grass: corn. Corn is the perfect industrial food product. It is fungible, tradeable, calorific, and almost infinitely processable. Here’s Pollan:

Corn is what feeds the steer that becomes the steak. Corn feeds the chicken and the pig, the turkey and the lamb, the catfish and the tilapia and, increasingly, even the salmon, a carnivore by nature that the fish farmers are reengineering to tolerate corn. The eggs are made of corn. The milk and cheese and yoghurt, which once came from dairy cows that grazed on grass, now typically come from Holsteins that spend their working lives indoors tethered to machines, eating corn.

Head over to the fast food outlet, and you hit more corn:

A chicken nugget…piles corn upon corn: what chicken it contains consists of corn of course, but so do most of a nugget’s other constituents, including the modified corn starch the glues the thing together, the corn flour in the batter that coats it, and the corn oil in which it gets fried.

And don’t forget the fizzy drink that goes with it—after water, corn sweetener is their principal ingredient. Americans are, quite literally, “processed corn walking.”

The one undeniable, all-conquering, critic-silencing, election-determining benefit of industrialised food production is, of course, the price at the till. The great yellow Mississippi of zea mays  flooding from America’s Corn Belt (an area the size of California) translates into a superabundance of cheap food in the supermarkets. And that too often is where the argument ends.

But other voices are being heard, and not just Pollan’s. As Jonathan Foley outlined earlier this year in Scientific American the price at the till does not reckon a host of other costs. And they are staggering: the depletion of waterways, the degradation of penned livestock, the devastation of landscape and wildlife, soil erosion, the impact of chemical run-off—including the blooming of a vast hypoxic “dead zone” the size of Connecticut in the Gulf of Mexico. And not forgetting the dubious nutritional quality of so much processed food, and the hand it has in the stratospheric levels of American obesity. According to Foley, vast agricultural monocultures are also scarily vulnerable to shocks: fluctuations in grain prices, novel pests, overseas competition. Over-reliance on corn represents a “systemic risk to America’s agriculture.”

But the news is not all bad. In The Omnivore’s Dilemma Pollan spends a week working at Polyface farm—self-described “beyond organic”—in the Shenandoah valley in Virginia. From a hundred acres of sustainable pasture spread among forest, it grows food of extraordinary diversity and quality. Through what Pollan calls an “intensive rotational dance” where half a dozen varieties of livestock are raised in symbiosis, the farm is one of the most productive in America. It is also one of the greenest. It feeds itself, fertilises itself and even de-bugs itself—chickens follow the cows and eat the parasites, they root through the rabbit mulch in search of earth worms, rendering their powerful urine innocuous. It is very difficult not to fall for such a pastoral idyll.

But there is a but. The food is expensive. It is sold to restaurants, to the affluent, or to those who take their food seriously. So the big question—the question that we need somehow to answer—is can it be scaled up? And this is where the real thinking needs to be done. The external costs of cheap food are horrific, and in the long run unsustainable. Our relationship with food, which both drives industrial  production and is driven by it, is damaging us. These are among our biggest contemporary public health and bioethical challenges. The gains of industrial food production have been extraordinary. According to Pollan, many more of us now suffer from the effects of over-eating rather than malnutrition. But those costs not carried to the till are going to overwhelm us. It seems we need to take another long look at those grains of grass, for the world we currently see in them is not working.

Julian Sheather is ethics manager, BMA. The views he expresses in his blog posts are entirely his own.