Salt or the Only Rock We Eat

There is a small dish of salt on the table in front of me as I write this, and it is worth stopping to consider how strange that is. Everything else I might put in my mouth today was once alive: the bread was wheat, the cheese was milk, the oil was a fruit crushed on a hillside. Salt alone is a mineral. It is a rock. We dig it out of the ground or boil it out of the sea, and then we sprinkle it, without a second thought, onto nearly everything we eat. It is the only rock in the human diet — the single inorganic thing we crave, seek out, fight over, and cannot live without.

We cannot live without it literally. The body runs on a faint salinity, an inheritance from the ocean where life began; our blood is salt water at roughly a third the concentration of the sea, and every nerve impulse and muscle contraction depends on sodium moving across a membrane. A person entirely deprived of salt will, in time, die. For most of human history, getting enough of it was a genuine and pressing problem — which is precisely why salt, this cheap white stuff we now leave in open bowls and knock onto the floor without noticing, was for thousands of years one of the most valuable substances on earth.

The word itself is a fossil of that value. The Latin for salt is sal, and Roman soldiers were, according to a tradition at least as old as Pliny, given an allowance connected to it — a salarium, the salt-money — which is the direct ancestor of the English word salary. Whether the coins literally bought salt or the phrase was already a figure of speech by Pliny's day is disputed by scholars, and I am inclined to distrust any etymology this tidy. But the deeper point stands regardless of the details: salt and money and worth were so entangled in the ancient mind that the words grew into one another. To be "worth your salt" is to earn your salary, which is to earn your salt, and the whole knot of expressions comes from a time when salt genuinely was a form of wealth.

It made and unmade cities. Rome's oldest road, the Via Salaria, was the salt road — the route by which salt from the pans at the mouth of the Tiber was carried up into the Sabine hills, laid down before the Republic itself. Venice built its early fortune not on spices but on salt, cornering the trade around the northern Adriatic and using the profits to fund the fleet that would later carry everything else. The German towns whose names end in -halle or begin with Hall—Halle, Hallstatt, Hallein, Schwäbisch Hall—are salt towns, named from an ancient root for the stuff; Hallstatt in the Austrian Alps has been mining salt from the same mountain for something like seven thousand years, which makes it one of the oldest continuous industrial operations on the planet. Timbuktu grew rich because it sat where the salt caravans from the Sahara met the gold of the south, and there were long periods and places in West Africa where salt traded, weight for weight, against gold itself — a block of rock salt for its own mass in the most precious metal known.

The French monarchy taxed it, through the notorious gabelle, a salt tax so hated, so unequal from province to province, so aggressively enforced against the smugglers who ran salt across internal borders, that it became one of the standing grievances that fed into the Revolution. Gandhi, closer to our own time, understood the same thing in reverse: that a government's monopoly on so basic a substance was a lever of control, and that to walk to the sea and make salt in defiance of the British salt laws was to strike at the empire in a place everyone could feel. The Salt March of 1930 worked as protest precisely because everyone, of every caste and income, needed salt, and everyone understood at once what it meant to make your own.

For most of that long history, though, salt's supreme value was not as a seasoning at all. It was as the thing that kept food from rotting — the only reliable defence, before refrigeration, against the constant threat of the larder going bad.

This is the salt that built entire cuisines. Salt cod — bacalhau, baccalà, bacalao — was the protein that let Basque and Portuguese fishermen sail to the cod banks off Newfoundland and bring the catch home across an ocean without a scrap of ice; the fish was split, salted, and dried into boards that would keep for a year, and it fed Catholic Europe through every meatless Friday and every Lent for centuries. Portugal alone is said to have a different bacalhau recipe for every day of the year, all of them descended from that one act of preservation. Prosciutto, jamón, the whole glorious civilisation of dry-cured ham, is salt and time and nothing else — a pig's leg buried in salt, then hung in the air for a year or two or three while the salt draws out the water and holds off decay long enough for something extraordinary to happen instead. Sauerkraut, kimchi, olives, anchovies, feta in its brine, the salt-cured lemons of Morocco, the fish sauce that the Romans called garum and fermented in vats along this same Mediterranean coast — all of them are salt doing its ancient double work: killing what would spoil the food, and, almost incidentally, transforming it into something better than it was before.

Whole economies of taste, in other words, exist only because salt exists. Take it away and you do not merely have blander food; you have no ham, no cheese that lasts, no preserved fish, no way for a northern winter or a long sea voyage to be survived. Salt is the reason a great deal of the food we think of as luxurious and traditional exists at all.

And then, in the space of a single century, the whole picture inverted.

Refrigeration arrived, and salt's great preservative job largely vanished — we no longer need it to survive the winter, because the winter now lives in a white box in the kitchen. At almost the same moment, salt became, for the first time in human history, absurdly cheap and effortlessly abundant. The substance men had died for, taxed empires with, and hauled across deserts on the backs of camels could now be bought for pennies in a cardboard cylinder. Something that had been precious for ten thousand years became, overnight, one of the cheapest things in the shop.

The trouble is that our bodies and our tastes were shaped by all those millennia of scarcity. We evolved to love salt, to seek it out, because for our ancestors the danger was always getting too little. Almost nobody, in the whole long human story, had the problem we now have: getting far, far too much. The salt is no longer mostly in the bowl on the table, where we can see it and control it. It is hidden, in industrial quantities, inside the bread and the sauce and the soup and the crisps and the cured everything — the processed food that now makes up the bulk of what many people eat, and that carries a load of sodium our salt-hungry instincts never evolved any brake against.

Here I have to put down the celebration for a moment, because it would be dishonest not to. Too much salt, sustained over years, does real harm. The clearest link is to blood pressure: a diet heavy in sodium tends, in a great many people, to push blood pressure up, and high blood pressure is one of the quiet, patient drivers of heart disease and stroke — dangerous precisely because it does its damage without symptoms, for years, until it doesn't. This is not food-scold fussiness; it is about as well-established as anything in nutrition gets. The mineral that kept our ancestors alive is, in the abundance of the modern diet, shortening a good many lives.

And so I want to spare a genuine, sympathetic thought for the people who have been told they must give it up — the ones with hypertension, or heart trouble, or kidneys that can no longer manage the load, who have sat across a desk from a doctor and been instructed to take the salt away. It is a harder sentence than it sounds. Salt does not have a flavour of its own so much as it unlocks the flavour of everything else; it is the switch that turns a dish from flat to alive, and food without it can taste, at first, like a photograph of a meal rather than the meal. To be handed a plate of unsalted food after a lifetime of the seasoned kind is to feel that some essential brightness has been drained out of the world. I have cooked for people on strict low-salt diets, and the effort it takes — the lemon and the vinegar and the herbs and the toasted spices all drafted in to do the job that one pinch used to do — gives you a sharp new respect for how much work salt was quietly performing all along. If you are one of those people, reading this: I am sorry, and I see you, and I promise the acid and the herbs really can carry more of the load than you'd think, even if they never quite carry all of it.

Which returns me, in the end, to the small dish on my table, and to the peculiar privilege it represents.

I can leave salt sitting out in an open bowl, uncovered, unguarded, because it is worth almost nothing — and it is worth almost nothing only because, for the first time in ten thousand years, it is everywhere. Every previous generation of human beings would have found that dish astonishing: a fortune's worth of preservation and seasoning and, once, literal money, left carelessly open to the air as though it were sand. They fought wars over less than what I will knock onto the floor and sweep away this week.

So I try, now and then, to take the pinch deliberately — to lift it between finger and thumb the way you'd handle something that mattered, and scatter it over the tomatoes, and taste what it does. Because it is a genuinely marvellous thing, this only rock we eat: the mineral that carries the memory of the sea in our blood, that built roads and cities and cured the ham and salted the cod and paid the soldiers, and that still, in the right small amount, makes an ordinary tomato taste briefly like the best thing in the world. Worth its salt, as they used to say — back when that meant something, and, if you stop to think about it, still does.