The truth about lettuce and salad leaves

Bags of pre-washed mixed salad leaves are a staple of chefs and home cooks, but Joanna Blythman investigates what eating these greens really means…

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Older generations can still remember the typical 1950s salad that consisted of a couple of flaccid leaves of lettuce topped with boiled egg and tomato, temptingly garnished with that peculiar British condiment known as salad cream.
It felt like progress when the American iceberg lettuce arrived in the 1970s. We overlooked its almost total lack of flavour because it delivered a juicy crunch. The cabbage-like iceberg could be kept in the fridge, apparently fresh, for weeks on end. For a nation that ate green salad infrequently, more out of a sense of duty than anything else, the omnipresent iceberg was just the job.
 
British roots
Throughout the 1980s and 1990s, restaurants began to showcase more exciting salad leaves such as curly endive and oak leaf lettuce, stimulating consumer demand for what we took to be foreign varieties. In reality this was only reacquainting us with our long-lost salad tradition.
In 1699, the English gardener and diarist John Evelyn’s book, Acetaria, catalogued an astonishing diversity of plants that could be used for “sallet”. He even recommended “a particular Composition of certain Crude and fresh herbs, such as usually are, or may safely be eaten with some Acetous Juice, Oyl, Salt, &c. to give them a grateful Gust and Vehicle” that now sounds like what we know as a French dressing or vinaigrette.
Looking around at the profusion of lettuces and leaves now on offer, you can see how salad has rocketed – excuse the pun – up the UK culinary agenda. Many restaurants rely on a tangle of leaves to bulk out and add interest to their dishes. On the domestic front, the puffy pillow packs of pre-washed salad leaves have overtaken frozen peas as an effortless vegetable add-on for home cooks.
Munching much more leafy salad than ever before ought to be good for us. Though they are often dismissed as being mainly water, salad leaves have valuable levels of vitamins, minerals and antioxidants that we particularly benefit from because we eat them raw. However, research suggests that bagged salads have fewer nutrients than the freshly cut equivalent. Why is this? It could be the effect of the nitrogen and carbon dioxide that keeps the leaves looking fresh and green beyond their natural shelf-life, or because the leaves may be older than the whole, unprocessed sort by the time we eat them.
Torn leaves, of the type found in these packs, quickly lose their vitamin C and folate content. The leaves are also often washed in water treated with chlorine, an oxidising disinfectant, at up to 20 times the concentration you would find in a swimming pool, according to some sources. This could also interfere with the nutrient levels. Some retailers now have their salad leaves washed in more benign spring or ozonated water instead, to improve the taste and reduce the chance of chlorine by-products lingering on the leaves; but unless your salad bag label says otherwise, assume that chlorinated water has been used.
 
Pesticide fears
Due to their open, leafy shape, lettuces and salad leaves are particularly prone to trapping pesticides and, since 1994, government testing of UK-grown salad leaves has revealed an ongoing problem with pesticide residues; so much so that the government now checks them on a quarterly basis. Of 34 lettuces tested in 2008, 30 had residues, although not at levels that, according to UK pesticide monitoring authorities, would harm human health. The residue problem particularly relates to winter lettuces grown this way, because they endure heavy fungicide treatments to cope with the damp conditions.
Lettuces and salad leaves were traditionally grown outdoors in open fields; nowadays many are now cultivated in polytunnels or glasshouses to provide an all-year supply. This protected environment creates a perfect climate for the development of rot and carry-over of disease from one harvest to the next.
 
The quest for freshness
If all this talk of chemical residues and lost nutrients is turning you off eating lettuce, do not despair. There is still a profusion of wonderful leaves to be had in Britain, but it might just take a little more effort to locate it. If you buy fresh whole lettuces and leaves that have not been packed in modified air, you can assess the freshness more easily and then wash them yourself. Puffy packs of salad leaves may look good when you buy them, but often flop dramatically when exposed to air, and many believe that they just don’t have the natural vitality of freshly picked leaves. If you feel daunted or bored at the thought of getting through a whole head of lettuce, check out the fresh mixed leaves selections on farmers’ markets stalls, from box schemes and farm shops, which usually offer an interesting array of salads.
All manner of salad leaves are ours for the tasting. Fascinating newcomers from as far afield as Japan now complement neglected native varieties, and this diverse selection is now in small-scale commercial production around the UK. Our salad bowls have perked up no end.
 
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