A bulletin for the Australian Food Industry    February 1998

Contents: Maximum, safe food cooling times in food service situations | FDA approves irradiation of red meat | Monosodium glutamate revisited | Ochratoxin A in foods | AQIS Imported Food Inspection Program | Chlorine under challenge

Monosodium glutamate revisited

Monosodium glutamate (MSG) remains one of the most discussed and studied additives/ingredients in our food supply. In 1987 the Institute of Food Technologists' Expert Panel on Food Science and Nutrition described MSG as a 'safe, efficacious flavour enhancer for the vast majority of the population.' The Federation of American Societies for Experimental Biology (FASEB) in a review sponsored by the FDA in the United States concluded in 1995 that an effect of MSG will be seen only when large doses, 3g or more of MSG or other free glutamate, are consumed without food. However the report did recognize a cluster of symptoms in a small proportion of individuals which it termed MSG symptoms complex. This complex is similar to the range of symptoms commonly referred to as Chinese restaurant syndrome following a letter by Kwok to the New England Journal of Medicine in 1968.

A recent report in the Journal of Allergy and Clinical Immunology 99 (6 part 1) 1997 757-62 provides probably the strongest experimental evidence yet of the reality of this MSG symptom complex under the conditions studied.

The authors of the report (Yang et al.) note that the majority of earlier reports have been anecdotes or the methodology of experimental studies has been open to criticism and has been challenged by various parties. To address the issue of the validity of the symptoms described, the authors conducted a double-blind, placebo-controlled challenge study in self-identified MSG sensitive subjects in which the taste of MSG was disguised in a strongly citrus tasting beverage. They stress that the objective of the study was to examine the Chinese restaurant syndrome and not to assess other reported reactions to MSG such as anaphylaxis or asthma.

The results obtained suggest that sensitivity to MSG exists at least in the testing situation used and is characterized by numbness, tingling, headache, muscle tightness, general weakness and flushing.

In the study, the MSG was administered to self-identified sufferers in the liquid beverage on an empty stomach. A threshold dose of 2.5g MSG was identified and the frequency and severity of responses increased with increasing doses. This supports the FASEB conclusion cited above. The study has relevance to everyday situations because, as the authors say, large doses of MSG may be ingested at the beginning of a meal, akin somewhat to receiving MSG on an empty stomach and quite different from receiving MSG equally throughout the meal or most of the MSG toward the end of the meal.

The 1987 conclusion of the IFT Expert Panel remains valid however. People who wish to avoid MSG must study the ingredient listing of packaged foods - the additive code number for MSG is 621 - and avoid those eating out situations where uncertainty about the ingredients used in meal preparation exists.