WHAT could be better on a cold day than to be wrapped around a bowl of hot soup, with full, brothy flavours overwhelming one's palate? Chances are, though, those taste buds are being duped.
The culprit, monosodium glutamate (MSG), is a matter of taste - more accurately, of increasing our perception of the flavour of food. While this might seem a good thing, in fact MSG can cause unpleasant reactions and even be dangerous, at least for those who have an adverse reaction to the substance. And anyone seeking to avoid it may find this more difficult than simply reading the list of ingredients. Glutamate is an amino acid that exists naturally in our bodies and in protein-containing foods such as cheese, milk, mushrooms, meat, fish and many vegetables. When MSG, a synthetic derivative of glutamate, is added to foods in cooking, it functions as natural glutamate, enhancing the flavour of soups, stews, meat-based sauces and snack foods.
Monosodium glutamate, also known as €621, is used commercially in most powdered savoury foods such as soups (packaged stocks and bouillon) and sauces. It is also used in many low-fat meals to replace flavours lost in eschewing high-calorie and high-flavour ingredients. In its pure form, MSG is sold as a fine, white, crystal substance, similar in appearance to salt or sugar. The substance originated in Japan, where a nutritious sea-vegetable known as kombu has been used for centuries as a taste-enhancer. In 1908, a Dr Kikunae Ikeda isolated the taste-enhancing glutamate from kombu. He set up a company which marketed what later became MSG.
Today, MSG is produced by a process of fermentation using starch, sugar beet or cane, and molasses.
Food scientists agree taste can be categorised into four groups: sweet, sour, salty and bitter. It is thought MSG creates a fifth category, a distinctive taste known in Japan as umami. This word has no direct translation in Western culture but it is best described as savoury, broth-like or meaty.
MSG remains a prevalent ingredient in Oriental cuisine. The consumption of MSG in Taiwan, for example, is 21 grams a week - significantly higher than the UK consumption rate of 4 grams a week. Such is demand for the enhancer that during the 1998 elections in Cambodia, families were solicited for votes with bags of the substance delivered to their homes as gifts.
It has no nutritional value, or flavour - it does not affect the food to which it is added: rather, it functions by stimulating the taste buds, changing the way you taste the food. But for a small proportion of people, MSG has rather different effects. In 1968, Robert Ho Man Kwok, MD, described a collection of symptoms he experienced after eating Chinese food. He coined the phrase "Chinese Restaurant Syndrome" to describe sensations of numbness at the back of his neck and a feeling of pressure in the face and upper chest-muscles. A host of other symptoms were attributed to the MSG used in Chinese food. The affliction was later renamed "MSG symptom complex" in 1995.
Those allergic to, sensitive to, or intolerant of MSG have been estimated to be less than 1 per cent of the population by American state agencies and as much as 25 per cent by American biochemists. Reactions to it range from slight discomfort such as heart palpitations, nausea and tremors to side-effects such as vomiting, asthma attacks and, in rare circumstances, anaphylactic shock.
Scientific research was first drawn to the effects of MSG by an article in the New England Journal of Medicine written by Dr John W. Olney in 1968. He linked brain damage in laboratory animals to MSG ingestion. In the late 1980s a book called In Bad Taste: The MSG Syndrome by Dr George Schwartz cited case-studies of MSG-sensitive individuals and revealed how MSG can be hidden in the ingredients of other food additives.
Another source of glutamate in food is hydrolysed proteins. The process used in their manufacture breaks proteins down into amino acids, but the process yields a high concentration of free glutamic acid. This poses the same threat as MSG to those sensitive to the additive because MSG is composed of 99 per cent free glutamic acid.
In August, 1995 the US Truth in Labelling Campaign brought a case seeking full disclosure of MSG in foods to the Federal Court, but it did not win the desired changes. Under American Food and Drug Administration regulations, MSG must be identified on labels - but food manufacturers are not obliged to label MSG in hydrolysed proteins on their products and, in some circumstances, can even label these additives as "natural flavours" - reasoning that glutamate is taken from naturally occurring proteins.
It is, therefore, often extremely difficult to tell whether MSG is present in food you dish up yourself - never mind what you eat in restaurants. Few restaurant staff know whether there is MSG in the food they serve - or of its effect on a minority of people.
One Dublin restaurant, Trastevere in Temple Bar, carries a "100 per cent MSG free" label on its menu to allay customers' fears. The restaurant manager, Karen Potter, lays down the restaurant policy in unequivocal terms: "Our food is fresh and made from scratch. There are no enhancers in our food, it's honest to goodness . . . no cheating!"