China's barber shops are about the last place you might expect to find a food ingredient. None the less, this is where the food industry obtains a good proportion of the raw material - human hair - for one of its favorite additives. It is commonly seen on packaged food ingredient lists as L - cysteine, or L - cysteine Hydrochloride (HCL). The additive can be produced in two ways: synthetically, from non-organic bases such as petroleum, or directly from human hair. It can be much cheaper to use human hair, which contains up to 8 per cent of the natural amino acid cysteine.

Cysteine is used as a flavoring and a dough enhancer, but by the time it reaches our pizzas and snacks the hair has been thoroughly processed and reduced to its chemical constituents. Still, it is extraordinary to think that the body can be recycled and re-enter the food chain so abruptly. More extraordinary, perhaps, is the journey it makes from the the Far East to our food. Why the food - additives industry should favor hair from this particular region is clear: its homogenous abundance - China has a head count of one billion - and according to the food - ingredient expert Dr John Meyer, because "it's easy to collect nice, clean, tied - up bales of human hair there". The hair is collected, cleaned, processed and then chemically converted into L - cysteine in Far East factories.

"There are very few renewable human resources, but cysteine is one of them," says Dr Meyer, who is responsible for sourcing kosher foods for the Jewish Orthodox Union of America. "You often find it in yeast flavors and you might find it in a savory flavor for almost anything." Muslims are also aware of its presence in food. According to Koranic law, Muslims are forbidden to eat anything containing L - cysteine because it may be derived from human hair. America is ahead in keeping track of all the added ingredients in processed food - kosher food marked with a "U" on the ingredients means it is free of L - cysteine, but elsewhere in the world there is no standard method of identifying foods containing L - cysteine.

"L - cysteine may be present in a number of foods, but it is not always listed on the ingredients," says Richard Ratcliffe, the executive secretary of the British Food Additives and Ingredients Association. "Additives regulations in Europe require manufacturers to list additives and class them as a coloring, for example. But L - cysteine is not regarded as a food additive. It is seen as a processing aid. The food processors decide whether or not to list something like L - cysteine depending on the amounts used. "Nor, of course, do the manufacturers have to state if the L - cysteine used is hair-derived or otherwise."

"The chemical process of converting hair to food additive has been known for a hundred years and couldn't be simpler," says Professor Derek Burke, the former chairman of the Advisory Committee on Novel Foods and Processes. For those of us who do feel queasy about hair chemicals in food, not only may the use of cysteine seem cannibalistic, but there are also chilling associations with Auschwitz, where it was produced in a hair - chemicals plant. But if cysteine's provenance appears somewhat stomach-turning, then consider the chemical's benefits. Health - supplement fans rave about it. According to a health-products retailer, cysteine is one of the body's most effective anti-oxidants and destroyers of the metabolism's toxic waste products, that are said to accelerate aging. Cysteine is also naturally produced in sulphur-containing foods such as egg yolks, red peppers, garlic, onions, broccoli and Brussels sprouts.

The Government's of America and Europe believe cysteine, human hair-derived or otherwise, as a perfectly safe. In fact, the view is that it is just one of several additives regarded as essential if we are to continue to enjoy safe, cheap food with a long shelf life. And, say its champions, since cysteine is hairy by nature, it can help prevent hair loss and stimulate its growth.

Ya want fries with that?