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Monosodium Glutamate, monosodium glutamate, MSG, Monosodium Glutamate, monosodium glutamate, MSG, Monosodium Glutamate, MSG
Basic Facts About Processed Free Glutamic Acid (MSG)

MSG-sensitivity is a sensitivity to free glutamic acid that occurs in food as a consequence of manufacture. All protein contains glutamic acid bound in it, but only when glutamic acid has been freed from protein before it is eaten do people have MSG-sensitivity reactions, provided that they ingest amounts that exceed their individual tolerance levels. Some unadulterated protein may have minute amounts of free glutamic acid associated with it, but MSG-sensitive people do not generally report adverse reactions following ingestion of unadulterated protein. Any free glutamic acid freed from protein during processing can cause MSG reactions. The source of the hydrolyzed protein (soy, corn, etc.) appears to be irrelevant.

MSG is manufactured through a process of protein hydrolysis, wherein glutamic acid is freed from protein through fermentation or use of chemicals or enzymes. MSG is also manufactured by what is referred to as a fermentation process wherein bacteria are grown aerobically in a liquid nutrient medium. The bacteria have the ability to excrete glutamic acid they synthesize outside of their cell membrane into the liquid nutrient medium in which they are grown. The glutamic acid is then separated from the fermentation broth by filtration, concentration, acidification, and crystallization, and converted to its monosodium salt.(1) With some exceptions, the FDA requires that ingredients -- MSG-containing ingredients included -- must be called by their common or usual names. The name "monosodium glutamate" is reserved for the ingredient that is a 99% pure combination of glutamic acid and sodium. The names of most other MSG-containing ingredients won't give consumers even a clue to the fact that the ingredients contain MSG. "Monosodium glutamate," "monopotassium glutamate," "autolyzed yeast," "hydrolyzed soy protein," and "sodium caseinate," are examples of ingredients that always contain MSG.

Under certain circumstances, hydrolyzed protein products may be used as ingredients in other products without even mention of the original hydrolyzed protein products. For example, "hydrolyzed soy protein," when used in "flavoring(s)," "natural flavoring(s)," and "natural flavor(s)," does not have to be mentioned on product labels when the food processor claims that the hydrolyzed protein is being used for purposes other than flavoring. In addition, MSG-containing products such as broth, bouillon, and stock, when used as ingredients in other products, do not have to disclose their MSG-containing components--not even by their common or usual names.

Use of MSG in food continues to grow. MSG is found in most soups, salad dressings, processed meats, frozen entrees, ice cream, and frozen yogurt; in some crackers, bread, canned tuna; and very often in "low fat" foods to make up for flavor lost when fat is reduced or eliminated.

In 1998, the U.S. Environmental Protection Agency approved spraying processed free glutamic acid (MSG) on crops as they grow. (See MSG is Sprayed on Growing Fruits, Grains, and Vegetables)

In 1969, Schaumburg et al. determined that approximately 30% of our population suffered adverse reactions when fed MSG in an ordinary diet.(2) Reif-Lehrer(3) and Kenney and Tidball(4) confirmed his findings. Those studies were challenged by Kerr et al. in a 1979 glutamate industry sponsored study.(5) Kerr et al. found that 43 per cent of respondents reported one or more unpleasant symptoms associated with eating, but concluded that only 1.8% of the population might be sensitive to MSG. To accomplish this, Kerr et al. decreed that the only true symptoms of MSG-sensitivity (called "Chinese restaurant syndrome"), were "burning, tightness, and numbness," experienced simultaneously, that commenced between 10 minutes and 2 hours after the start of a meal, and lasted 4 hours or less. Kerr et al. had to ignore all other reported symptoms, even migraine headache,(6) in order to come up with this 1.8% figure.

Given increased use of MSG since 1979, we would now expect more than 30% of the population to suffer adverse reactions to MSG from time to time.


1. Leung, A. and Foster, S. Encyclopedia of common natural ingredients used in food, drugs, and cosmetics. New York: Wiley, 1996.

2. Schaumburg, H.H., Byck, R., Gerstl, R., and Mashman, J.H. Monosodium L-glutamate: its pharmacology and role in the Chinese restaurant syndrome. Science 163: 826-828, 1969.

3. Reif-Lehrer, L. A questionnaire study of the prevalence of chinese restaurant syndrome. Fed Proc 36:1617-1623, 1977.

4. Kenney, R.A. and Tidball, C.S. Human susceptibility to oral monosodium L-glutamate. Am J Clin Nutr 25: 140-146, 1972.

5. Kerr, G.R., Wu-Lee, M., El-Lozy, M., McGandy, R., and Stare, F. Food-symptomatology questionnaires: risks of demand-bias questions and population-biased surveys. In: Glutamic Acid: Advances in Biochemistry and Physiology Filer, L. J., et al., Eds. New York: Raven Press, 1979.

6. Food and Drug Administration (FDA) Health Hazard Evaluation Board (Monitoring System). Report on all adverse reactions in the Adverse Reaction Monitoring System. Memorandum from Sean F. Altekruse, DVM, MPH, Acting Chief and Ms. Donna M. Gray, Technical Information
Specialist, Epidemiology Branch, FDA. 2/28/94.

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This page was last updated on June 7, 2004.