The Recipe Left Behind

Almost every plant has some way of getting its seeds into the ground: it drops them, flings them, floats them or gets an animal to carry them. Maize has none. Leave a field of it alone and it is finished. Each kernel is held tight to the cob, and the cob is wrapped in husks, so the seeds have no way out. If a ripe ear does fall to the ground, Paul Mangelsdorf, the American botanist who spent most of his career on the origins of maize, explained what happens next in Corn: Its Origin, Evolution and Improvement (1974):

Mangelsdorf was wrong about where maize came from, but right about this. The ear, he wrote, "is superbly constructed for producing grain under man's protection, but it has a low survival value in nature, for it lacks a mechanism for dispersal of its seeds." One of the great grains of the world cannot sow itself. Almost every maize plant alive is there because somebody shelled a cob and planted the kernels.

That is because people made it. About nine thousand years ago, in the Balsas River valley in the south-western highlands of Mexico, farmers began to tend a wild grass called teosinte. It looks nothing like maize. Teosinte is bushy and branched, and its "ears" are tiny things, more like a head of wheat, holding perhaps ten or a dozen kernels, each shut inside a hard, inedible case. When they ripen, the ears break apart and scatter. It is a fine wild plant and a terrible dinner.

Over thousands of years of choosing seed, the farmers changed it, flipping genetic switches they knew nothing about. A change in how one gene, teosinte branched1, is regulated helped turn the bush into a single tall stalk. A single change in another, tga1, took away the stony case. "So, the kernel ends up naked, uncovered and exposed on the surface of the corn cob, to be eaten," said John Doebley, the University of Wisconsin geneticist whose laboratory found both. A teosinte ear holds about a dozen kernels. A large maize cob can carry twelve hundred.

In the Popol Vuh, the sacred book of the K'iche' Maya of Guatemala, the gods try several times to make human beings and fail, until at last they make them out of maize. It is a lovely idea, and botanically it runs both ways. People were made of maize, and maize was made by people.

But the bargain had a second clause, and it is the one this story is about. Maize is a superb food in almost every way but one. The body needs niacin, vitamin B3, and gets it in two ways: ready-made from food, or by making it from tryptophan, one of the building blocks of protein. Maize fails on both counts. Like other cereals, it keeps most of its niacin chemically fastened to larger molecules, in a form the gut can make little use of; only about a quarter to a third of it is thought to be available. And its main protein is poor in tryptophan. A diet of little else but maize is a diet short of niacin, however much maize there is. The food has the vitamin and won't hand it over.

The people who made maize had solved that too, long before anyone knew there was a problem. When maize travelled the world, the solution stayed at home. What followed, for two hundred years and on two continents, was a disease that doctors blamed on germs, on poison, on insects, on heredity and on bad housekeeping. Its real cause was a recipe nobody had brought along.

Ash-water

In Nahuatl, the language of the Aztecs, the word is nixtamalli. It is built from nextli, "ash", and tamalli, maize dough. Dried kernels are soaked and simmered in water made alkaline with wood ash or lime, then left to steep, sometimes overnight. The skins slip off. The grain softens and can be ground on a stone into masa, a dough that holds together, as plain maize flour will not. From masa come tortillas and tamales.

Nobody knows how this was first worked out; one idea is that cooks boiling maize with hot stones, where the bedrock was limestone, found the stones did it for them. The earliest evidence for the practice comes from the southern coast of Guatemala, from between 1500 and 1200 BC. By about 900 AD it had spread north to the peoples of the Mississippi valley and the American south-east, as hominy.

The cooks were not taking a vitamin supplement. The ash-water made maize easier to peel and grind, better to eat, and able to make a dough. That the same pot made the grain more nourishing was, as far as anyone can tell, a happy side effect. Alongside it, in the same fields and on the same plates, went beans, which supply what maize protein lacks. Through three thousand years of eating this way, people rarely suffered from the disease this story is about. They had the plant and the recipe together, and the recipe was part of what maize was.

Turkey wheat

Then the plant crossed the Atlantic, and the recipe didn't.

The grain travelled beautifully. It was growing in Spain within a few decades of Columbus, and soon in Italy, West Africa and the Philippines. It gave more food from a field than the old grains, which mattered to the poor. The English called it Turkey wheat. José de Acosta, the Spanish Jesuit who wrote one of the first natural histories of the Americas, ranked it in 1590 with something close to theological precision:

To conclude, God hath imparted to ev'ry region what is needefull. To this continent he hath given wheate, which is the chiefe nourishment of man; and to the Indians he hath given Mays, which hath the second place to wheate, for the nourishment of men and beasts.

José de Acosta, Historia natural y moral de las Indias (1590), in Edward Grimston's English translation of 1604

Second place, and shared with the animals. That was roughly how Europe treated it, which may help explain why nobody thought to bring the cooking. Seeds are easy to carry. A kitchen practice is not: it lived in the hands of the cooks, and to a European eye it looked like a lot of trouble over a cheap food. Even in North America, where settlers could watch it being done, they rarely took it up; they thought it unnecessary, and they did not like the taste. So maize arrived in Europe as a grain to be ground and boiled like any other. By the eighteenth century it was the chief food of the poor in southern France and northern Italy, eaten as polenta, often with very little else.

In 1735 Gaspar Casal, a doctor in Oviedo in northern Spain, described a disease among the poor peasants of Asturias, who lived mostly on maize and rarely ate meat. It started with the skin: a red, rough rash on the backs of the hands and feet, wherever the sun touched. He called it mal de la rosa, the rose sickness; the band of rash round the neck is still called Casal's collar. In 1771 Francesco Frapolli, a doctor in Milan, gave it the name that stuck, from the Lombard for rough skin: pellagra.

The rash was only the beginning. Doctors later learnt to recognise the disease by four Ds: dermatitis, diarrhoea, dementia and death. In Lombardy, the region around Milan, some 39,000 cases were recorded in 1862 alone, among two and a half million people. By the 1880s there were more than 100,000 pellagrins in Italy.

Everyone could see that pellagra followed maize. The question was how. Cesare Lombroso, the Italian doctor better known for his theory of the born criminal, was the most famous of those who decided that the grain must be spoiled, carrying a fungus or a poison. Others blamed an infection, perhaps spread by insects. Lombroso was half right, the most frustrating way to be right. It was the maize. It was not maize gone bad. It was maize that had never been cooked the way its makers cooked it.

Meat, meal and molasses

The disease reached the American South last. The diet was already there, waiting. Mary James, interviewed in Baltimore in the 1930s about her childhood enslaved on a plantation on the James River in Virginia, remembered the rations:

After emancipation, for a great many poor Southerners, Black and white, sharecroppers and mill hands, those first three things were most of what there was. They had a name: the three Ms, meat, meal and molasses. The meat was fatback; the meal was plain ground maize. Cotton was planted right up to the cabin door, leaving no room for a garden or a cow. Nobody was starving. There were plenty of calories. They were simply the wrong ones.

From 1906 pellagra spread across the South as an epidemic. Between then and 1940 there were about three million cases in the United States, and something like 100,000 deaths. Most doctors thought it was an infection. A privately funded survey of 1912, the Thompson-McFadden report, found that pellagra clustered where sewers were bad, and that the best predictor of catching it was having neighbours who had it. That is exactly what an infectious disease looks like. It is also exactly what poverty looks like.

In 1914 Rupert Blue, the US Surgeon General, sent Joseph Goldberger to look into it. Goldberger, a doctor in the US Public Health Service, had been born in 1874 in a small town in the Kingdom of Hungary, now Giraltovce in Slovakia, and grew up on the Lower East Side of Manhattan. He had spent his career chasing infectious diseases, including yellow fever and typhus, and pellagra did not behave like one. His first clue came from the orphanages and asylums. They had hundreds of cases among the inmates and none among the doctors and nurses, who were with the patients every day. A germ does not check who is on the staff. The staff, however, ate different food.

So he changed the food. In a few orphanages and asylums with high rates of pellagra, he added fresh meat, milk, eggs, peas and beans. The cases stopped, and some asylum patients recovered so far that they were sent home. Then he set out to cause it. In 1915, with the agreement of Mississippi's governor, Earl Brewer, eleven healthy volunteers at the Rankin State Prison Farm, who had been promised pardons, were put on a diet of grits, mush, biscuits, syrup, sweet potatoes, cabbage and rice. At first they were delighted with all the biscuits they could eat. Within months they were weak and miserable, and six of them had the rash. "I have been through a thousand hells," one said. When the doors opened at the end, Goldberger said, they fled "like scared rabbits."

His opponents still insisted on a germ. So in the spring of 1916 Goldberger held what have come to be called his filth parties. Sixteen volunteers, most of them doctors and one of them his wife, Mary, swallowed pills of flour mixed with the scabs, urine and faeces of pellagra patients, or took their blood by injection. "If anyone ever got pellagra that way, we . . . should certainly have it good and hard!" Goldberger said afterwards. "We just feasted on filth." Nobody caught anything.

It did not settle the matter. To many Southern doctors and politicians, Goldberger was a New York Yankee blaming the South's disease on the South's poverty. One newspaper declared that pellagra "should be a stigma on any housewife". Goldberger's despair has a modern ring to it: "I'm only a bum doctor. What can I do about the economic conditions of the South?"

What he could do was find something cheap. A few cents' worth of brewer's yeast prevented the disease, and after the great Mississippi flood of 1927, yeast in the refugee camps' food helped to control an outbreak. He died in 1929, sure that a nutrient was missing, before anyone found it. In 1937 Conrad Elvehjem, a biochemist at the University of Wisconsin, extracted nicotinic acid from liver and showed that it cured black tongue, the canine form of pellagra, in dogs. Other doctors soon showed that it cured people too.

Then there was a small problem with the name. Nicotinic acid had first been made, in the nineteenth century, by breaking down nicotine. To keep the nutrient at a safe distance from the drug in tobacco, it was given a new name, made from nicotinic acid vitamin: niacin. During the Second World War, federal and state laws required it to be added to bread. Pellagra all but disappeared from the United States.

Why the ash works, and an honest doubt

Here the story gets less tidy. Everyone agrees that maize cooked the old way does not cause pellagra the way plain maize does. What nobody has quite agreed on is why.

The usual explanation is that the alkali breaks the chains that bind maize's niacin and sets it free. A 2022 review in the journal Nutrients still describes alkali treatment as substantially improving the availability of the bound forms. But in 1992 the Food and Agriculture Organization of the United Nations, in its review Maize in Human Nutrition, called the question "extensively debated" and leaned the other way. The experiments it gathered suggested that lime mainly improves the balance of the protein, so the body can make more of its own niacin. Plain boiling, one study found, did much the same as lime. And in the most elegant test, researchers used cats, which cannot make niacin from tryptophan at all, and found that the cats took up the niacin from raw and limed maize equally well. If the lime were simply unlocking niacin, the cats should have noticed.

So the mechanism is contested; the recipe is not. Ash-water and a plate of beans did what Goldberger's yeast did, for three thousand years before anybody had a word for a vitamin.

The terms still apply

Pellagra is not a disease of the past. In 1990, among Mozambican refugees who had fled the war into Malawi, the ration of groundnuts, their main source of niacin, stopped for months. The rest of the ration was largely maize. Between February and October, 17,878 cases of pellagra were reported among about 286,000 refugees. The US Centers for Disease Control called it "the most extensive reported in the world since World War II". The plant had not changed its terms.

That, in the end, is the oddity at the centre of the story. Maize cannot sow its own seed, and it turns out that it depends on us twice. Once in the field, where someone must shell the cob and space the kernels. And once in the kitchen, where someone must cook it in ash. Europe took the first half of that bargain gladly, because the seeds were in its hands. The second half was in the hands of cooks on the other side of the ocean, and nobody thought it was worth asking for.