Has fast-food culture turned a British staple into an agent of poisoning?

How ironic that the healthy, chlorophyll-packed lettuce should be tainted by the dreaded salmonella. With battery-farm eggs, dubious sausages or grease-packed burgers, such contamination comes as no great surprise. But lettuce has been a symbol of health and fertility since 4500BC, the era of the Middle Kingdom of Ancient Egypt.

How ironic that the healthy, chlorophyll-packed lettuce should be tainted by the dreaded salmonella. With battery-farm eggs, dubious sausages or grease-packed burgers, such contamination comes as no great surprise. But lettuce has been a symbol of health and fertility since 4500BC, the era of the Middle Kingdom of Ancient Egypt.

As Jane Grigson points out in her Vegetable Book, a very detailed relief of three tall, cos-style lettuces appears among the carvings at Karnak. They form the background to an image of Min, the god of fertility. The phallic shape and milky fluid of the lettuce may have caused it to be regarded as a promoter of potency.

During Greek times, the lettuce was regarded primarily as a medicinal plant but its application was utterly altered, since it was utilised as a narcotic. Few would claim lettuce as the most exciting of foodstuffs and, indeed, it has a mildly soporific effect when eaten. This is particularly pronounced in its stringy, wild form. Around 400BC, the great physician Hippocrates was advocating its consumption in his early diet book Regimen.

Intriguingly, our cos lettuce takes its name from the island of Kos in the Dodecanese, which also happens to be the birthplace of Hippocrates. Lettuce came to be widely cultivated by the Greeks and the Romans followed suit. In early Roman times, the leaves were eaten at the end of a meal to induce a mild doziness in the diner. In later years, it was eaten as a kind of hors d'oeuvre to tickle the palate. That indicates the increased domestication of the lettuce. As the strains were improved, they became less bitter and soporific in their effect.

When our supermarkets and restaurateurs crow about the range of salads they offer, it is worth bearing in mind that Pliny describes nine varieties of lettuce, including red and purple exotics, in the 1st century AD. Usually, the Romans ate it as a salad with dressing but the writer Apicius recommended lettuce purée with onions.

Though its fortunes wilted during the carnivorous Dark Ages, greenstuff enjoyed a revival in medieval times. An unfragrant character in Chaucer's Canterbury Tales is pithily described: "Well loved he garlic, onions and lettuce."

It seems the English peasantry chomped a wild form known as perennial lettuce. The domesticated strains we know today did not appear until the 15th century. It seems likely that they spread from Kos to Italy while the island was in Roman possession. From Italy, the fashionable new strains of greenery spread across Europe and even crossed the Channel.

The botanically-obsessed John Evelyn was the first to use the word "cos" in 1664, but lettuce seeds were exported from England to the new colony in North America as early as 1494. By the 17th century, more exotic strains were being grown. Lollo rosso may have become ubiquitous on British restaurant plates in the 1980s, but the great horticulturalist John Tradescant introduced a "red Roman lettuce" in 1629. Stripped of its outer leaves, one specimen weighed 17oz.

It was at this time that the lettuce established its long hegemony over the salad bowl. As John Evelyn put it, the lettuce "ever was and still continues the principal foundation of the universal Tribe of Salads; which is to cool and refresh." Not only did the lettuce offer invigorating nutrition, it also served a moral purpose in "upholding morals, temperance and chastity". Like a 17th-century version of our own Delia Smith, Mr Evelyn's directions for making salad are crisp, authoritative and dogmatic. "In the composture of a salad, every plant should come in to play its part, without being overpowered by some herb of a stronger taste ... like the notes in music, there should be nothing harsh or grating."

The idea that lettuce should be eaten before retiring for its physically calming properties seems to have faded away in modern times, except for one celebrated reference in the 19th century. That appeared in the best-read of all literary works with a horticultural theme - Beatrix Potter's Peter Rabbit. After consuming a surfeit of "shot" lettuces, the Flopsy Bunnies almost ended up in Mrs MacGregor's rabbit pie when they fell asleep because "the lettuces had been so soporific". Yet, it seems that Beatrix Potter was spot on in her knowledge of this unlikely psychotropic. "All the species of lettuce are narcotic to a greater or lesser extent," writes Tom Stobart in The Cook's Encyclopaedia. "Even the stems of bolted garden lettuces, if eaten in quantity, have been known to make people drowsy, even unconscious."

Though the species are unrelated, the smell of lettuce is rather like that of the opium poppy because they share certain alkaloids. Mr Stobart notes the milky latex from one species of lettuce is dried like opium and used as a raw material in drug manufacture.

For anyone accustomed to the vast range of salads and mescluns now available in our supermarkets, it would come as a nasty surprise if they were to be suddenly transported back to the Fifties. People may have been more polite, the streets safer, our atmosphere less polluted, but the salads were a disaster. Aside from watercress (very much a seasonal item in those days), the only greenstuff was a flaccid lettuce with the evocative name of butterhead. Invariably partnered by tinned salmon, this languid leaf had all the crunch of a Kleenex tissue - and about as much flavour. In order to render it palatable, people used to drench butterhead leaves in large globs of salad cream. The result was possibly as unappetising a salad as has ever been devised in the history of the world.

Despite the salmonella scare, this is a golden age for salad and lettuce in particular. From the handsome oak leaf lettuce to lamb's tongues, there is a wonderful range to choose from. The cos lettuce (known as romaine in the US) never tastes better than when anointed with a home-made Caesar salad dressing. A crisp lettuce such as iceberg makes the best of all salads when combined with eggs, tuna, tomatoes, olives and anchovies in what is called a Salade Niçoise. (Though the purist Jacques Medecin excludes lettuce entirely from the recipe for this classic in his book Cuisine Niçoise.)

I harbour reservations about the trattoria favourite of lollo rosso. For all its beauty, this gaudy leaf has as much flavour as a glass of Evian. Occasionally in dark restaurants, its resemblance to a rasher of bacon can provoke deep disappointment.

But the salad is by no means the sole culinary application of lettuce. The Larousse Gastronomique declares that "lettuce was eaten as a hot dish" until the mid-18th century. (Incidentally, this culinary Bible also believes that the English fondness for raw lettuce was entirely due to a French nobleman called the Chevalier d'Albignac.) Lettuce is certainly much underrated and underused as a hot vegetable.

Though food lovers might have known about lettuce soup and braised lettuce, this versatile greenstuff also plays a key role in Paul Heathcote's fillet of cod with lettuce, Jennifer Paterson's steamed salmon in lettuce leaves with egg and lemon sauce and Hugh Fearnley-Whittingstall's lettuce risotto. Not that the lettuce salad is without its adherents. The ever gutsy Fergus Henderson suggests you can enliven oak leaf lettuce with braised snails: "You can pick the snails yourself ... though it is quite emotional."

Yet the fortunes of this admirable, interesting and healthy greenstuff are now threatened, it appears by some gruesome goings-on in fast food joints in the Midlands and elsewhere. How come this country shows a unique propensity for taking a fine, wholesome comestible and transforming it into some kind of poison by carelessness, greed or lack of hygiene?

The fact is that lettuce isn't bad for us but the dubious specks of salad accompanying fast food might be. The lesson of this latest scare should be: carry on with the lettuce, but dump the doner.

FROM CRADLE OF CIVILISATION TO GRAVE OF HUMOUR

Lettuce was first cultivated by the Sumerians, who populated the southern part of present-day Iraq almost 6,000 years ago.

The ancient Greeks and Romans believed lettuce to be a sedative. Emperor Domitian would serve it before feasts, hoping to torture fellow diners by forcing them to stay awake in his presence.

Augustus Caesar is said to have commissioned a statue of a Romaine lettuce, believing the leaf had cured him of a grave illness. However, the "Caesar salad" was named after Italian immigrant Caesar Cardini, who tossed the first version of the dish in Tijuana, Mexico, in 1924.

Lettuce was introduced to Britain by the Romans. The word "lettuce" derives from its Latin equivalent, "lactuca", which refers to the vegetable's milky juice.

US President Thomas Jefferson grew 19 varieties of lettuce in his garden after he retired to Monticello, Virginia.

Shakespeare's Iago has a fascination with plants, and mentions lettuce in Othello: "Our bodies are our gardens, to which our wills are gardeners; so that if we will plant nettles or sow lettuce, set hyssop and weed up thyme . . . the power and corrigible authority of this lies in our wills" (Act 1, Scene 3).

Lettuce is the second most popular vegetable in the US, after potatoes. The average American eats about 30 pounds of lettuce per year.

Lettuce, a member of the sunflower family, is made up of 95.9 per cent water. The remaining 4.1 per cent includes fibre, sugar, carbohydrate, protein, nitrogen and 0.4 per cent fat.

There are four main lettuce groups: butterhead, crisphead, looseleaf and the romaine or cos. Iceberg lettuce is a crisphead variety that was shipped covered with heaps of ice during the 1920s.

Well-loved lettuce jokes include:

"Knock Knock?" "Who's there?" "Lettuce." "Lettuce Who?" "Lettuce in and we'll tell you."

AND...

A man goes to the doctor and says "Doctor, doctor! There's a piece of lettuce sticking out of my nose."

"It's okay, sir, I'll just apply a dressing."

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