MONOSODIUM glutamate or MSG, is a popular flavour enhancer used in many processed foods.

Known locally as “vetsin” and “Chinese salt”, it is considered an important ingredient to many popular Chinese dishes.

MSG is also widely used in restaurants and finds its way into home-cooked meals via condiments and prepared seasonings available in supermarkets.

However, in the last two decades, its use has become controversial because of reports of adverse reactions in some people after consuming MSG.

Research on the role of a glutamate in the nervous system has also raised questions about the safety of using MSG in food.

Every few years, the questions pops up again as a result of some study or research, only to be greeted by assertions of its safety for use in food backed by some other study or research.

The information overload could confuse anyone who wants to eat healthy and avoid additives unless they have the facts.

Glutamate refers to a group of chemicals that includes MSG.

MSG is the sodium salt of an amino acid known as glutamic acid and a form of glutamate that is packaged and sold as a fine white crystal substance, similar in appearance to salt.

It does not have a distinct taste of its own and scientists do not fully understand how it adds flavour to other foods.

However, they believe that MSG stimulates glutamate receptors on the tongue to boost meat flavours and meat-like flavours.

In Asia, a seaweed broth was originally used to obtain the flavour -- enhancing effects of MSG, but today MSG is made by fermenting starch, sugar-beets, sugar-cane or molasses.

The chemical glutamate is found naturally in many living things: human bodies, animals, plants and in protein-containing foods, such as cheese, milk, meat, peas and mushrooms.

Some glutamate exists in foods in a “free” form.

It is only in this free form that glutamate can enhance a food’s flavour.

Part of the flavour-enhancing effect of tomatoes, certain cheeses, and fermented or hydrolysed protein products such as soy sauce (seow) and teriyaki sauce is due to the presence of free glutamate.

Several studies have shown that the body can use glutamate as an amino acid and a nerve impulse transmitter in the brain. There is also glutamate-responsive tissue in other parts of the body.

Some researchers believe that abnormalities in the function of glutamate receptors might be a factor in certain neurological diseases like Alzheimer’s disease and Huntington’s chorea.

Direct injections of glutamate in laboratory animals have resulted in damage to nerve cells in the brain, but consumption of glutamate in food does not seem to cause this effect.

Studies also show that people normally consume dietary glutamate in large amounts and the body can metabolise glutamate efficiently, but the results of animal studies conducted in the 1980s raised a significant question: Can the consumption of MSG harm the nervous system?

In 1995, a report from the Federation of American Societies for Experimental Biology (FASEB), an independent body of US-based scientists, reaffirmed previously published reports from the US Food and Drug Administration (USFDA) stating that MSG is a safe food ingredient for most people when eaten at customary levels.

However, he FASEB report identified two groups of people who may develop a condition known as “MSG symptom complex.”

One group is those who may be intolerant to MSG when eaten in a large quantity.

The second group is people with severe untreated asthma.

These people, in addition to being prone to MSG symptom complex, may suffer temporary worsening of asthmatic symptoms after consuming MSG.

Although the USFDA has not fully analysed the FASEB report, they believe that it provides the basis for adequate glutamate labelling.

FDA is proposing that foods containing significant amounts of free glutamate (i.e. glutamate not bound up with protein along with other amino acids) declare the presence of the substance on the label, which would allow consumers to distinguish between foods with insignificant MSG levels and those that might contribute to a reaction.

Meanwhile, other health-conscious groups and individuals have called for an outright ban on the use of packaged MSG in processed foods and in restaurants.