WE all know how important taste and flavour are to our enjoyment of foods. Think of tasty fried rice, mouth watering Peking Duck, succulent sukiyaki or yummy pad thai.

All of these dishes have a factor in common - the presence of glutamate - that helps to impart that delicious taste. Many traditional Asian seasonings, such as fish sauce (nam pla) and soy sauce, also contain glutamate.

Glutamate, an amino acid, can be found naturally in foods or added as seasoning in the form of monosodium glutamate (MSG). Used in foods since the early 1900s, MSG is used to impart extra flavour to a variety of foods and dishes including soups, sauces and restaurant foods.

What is MSG

MSG is the sodium salt of glutamic acid (glutamate) - it's simply glutamate, water and sodium. Glutamate is an amino acid that is found naturally in many foods including breastmilk, dairy products, meat, mushrooms, seaweed, tomatoes, nuts, legumes and vegetables.

Glutamate is also produced by the body and is needed for metabolism and brain function. The body metabolises the glutamate added to foods (as MSG) in the same way as naturally occurring glutamate.

How is MSG produced

In the early 1900s, MSG was extracted from seaweed and other plant sources. Today, MSG is produced commercially by the fermentation of starch, sugar beets, sugar cane or molasses.

Why is MSG added to foods

MSG is added to foods as a flavour enhancer. It's used to season savoury dishes such as soups, snack foods, sauces and prepared meals. In restaurant dishes or home cooking, MSG can be added before or during cooking. It imparts a unique taste called "unami" which is a savoury or broth-like flavour.

How safe is MSG

There is a long history of use of MSG in foods dating back to the early 1900s. In 1958, the US Food and Drug Administration (FDA) classified MSG as a "generally recognised as safe" (GRAS) ingredient, placing it in the same category as vinegar, baking powder and salt. Since that time there have been several extensive scientific reviews on MSG.

1987: The Joint Expert Committee on Food Additives (JECFA), the scientific advisory body on food additives to the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) of the United Nations, placed MSG in the safest category of food additives.

1991: The European Commission Scientific Committee on Foods reviewed the safety of MSG and agreed with the JECFA classification.

1992: The American Medical Association Council on Scientific Affairs reviewed MSG and stated that MSG was generally safe.

1995: The Food and Drug Administration (USA) asked the Federation of the American Society for Experimental Biology (FASEB) to conduct another review of MSG. FASEB reported that MSG was generally safe.

2003: The Australian Food Standards Agency. Reaffirmed the safety of MSG.

2006: Consensus meeting on MSG, Germany. A group of experts met to update the safety review of MSG and concluded MSG can be "regarded as harmless for the whole population"

Are some people sensitive to MSG

There have been reports of "MSG sensitivity" over the years. However scientific studies have largely failed to support these claims.

"Chinese Restaurant Syndrome" (CRS) is the name given to a condition which causes a range of temporary symptoms such as headache, numbness/tingling and flushing. The term "CRS" was given to the condition because it occurred after sufferers ate food prepared in Chinese restaurants.

The Australian FSA Report (2003) found that "the studies conducted to date on CRS have largely failed to demonstrate a causal association with MSG" so it is unclear exactly what causes the condition which is thought to affect 1-2% of the population.

There have also been anecdotal claims about MSG and asthma. The most recent reviews on MSG and asthma (FSA 2003) state that MSG does not appear to be a significant trigger for asthma.

Although MSG is not believed to be an allergen, there may be a small percentage of people who may be sensitive to it. If large doses of MSG (in the absence of food), are given to subjects in a laboratory setting, a small number of people have been reported to suffer mild and temporary CRS-type symptoms.

If you feel you are sensitive to any foods or food additives, you should check with a qualified dietitian who can refer you for assessment. The normal diet contains a vast complex of various food components and ingredients and it can be very difficult to identify the actual cause of any sensitivity.

Can pregnant and breastfeeding women take MSG

Yes. Studies show that MSG can safely be taken by pregnant and lactating women. Glutamate, even at very high levels, is unable to cross the placental barrier. In a review of the effects of food and environmental agents on breastfeeding (American Academy of Pediatrics, 1993), MSG was found to have no effect on lactation and posed no risk to the infant.

Is MSG safe for children

Yes. Studies show that children as young as 12 months can metabolise glutamate as effectively as adults.

Is MSG high in sodium

No. MSG only contains about one third of the sodium found in table salt.

References:

1. Institute of Food Technologist Expert panel on Food Safety and Nutrition. Monosodium Glutamate. Food Technology, 41 (5):143-145, 1987

2. Federation of American Societies for Experimental Biology (FASEB). Analysis of Adverse reactions to monosodium glutamate (MSG). Prepared by the Life Sciences Research Office, FASEB, for the Center for Food safety and Applied Nutrition, US Food and Drug Administration, Bethesda, Maryland: FASEB, 1995

3. Joint FAO/WHO Expert Committee on Food Additives.L-glutamic acid and its ammonium, calcium, monosodium and potassium salts. In toxicological Evaluation of Certain food Additives and Contaminants, WHO Food Additive Series No.22. New York: Cambridge University Press, pp.97-161, 1988

4. American Academy of Pediatrics' Committee on Drugs. The transfer of drugs and other chemicals into human milk. Pediatrics, 93:137-150, 1994

5. Monosodium glutamate - a safety assessment. Technical report Series No. 20. Food Standards Australia New Zealand, June 2003.

6. Beyreuther HK, Biesalski JD, Fernstrom JD, Grimm P, Hammess WP , Heinemann U, Kempski O, Stehle P, Steinhart H and Walker R. Consensus Meeting: Monosodium Glutamate - an update. European J Clin Nutr, 61:304-14, 2007

• For more information visit the Asian Food Information Centre website www.afic.org. The Asian Food Information Center is a Singapore registered not-for-profit organisation. Its mission is to effectively communicate science-base information on food safety, nutrition and health information to media, regulators, food/health professionals, and consumers in the Asia region.

This story was first published in The Star on Feb 24, 2008.