Addictive Potential: Unknown
Emergency Room Visits Yearly: Unknown
Mandatory Minimum Sentence: None, Legal
Mechanism of Action: Rapidly Increases Glutamate
Monosodium glutamate, also known as 2-aminoglutaric acid, commonly known as MSG, Ajinomoto or Vetsin, is a sodium salt of glutamic acid. MSG is a food additive, popularly marketed as a “flavour enhancer”. It was discovered and patented in 1909 by Ajinomoto Corporation in Japan. In its pure form, it appears as a white crystalline powder; when dissolved in water (or saliva) it rapidly dissociates into free sodium and glutamate ions.
MSG stimulates specific receptors located in taste buds such as the amino acid receptor T1R1/T1R3 or other glutamate receptors like the metabotropic receptors (mGluR4 and mGluR1) which induce the taste known as umami, one of the five basic tastes (the word umami is a loanword from Japanese; it is also referred to as “savory” or “meaty”).
Studies have shown that the body uses glutamate, an amino acid, as a nerve impulse transmitter in the brain and that there are glutamate-responsive tissues in other parts of the body, as well. Abnormal function of glutamate receptors has been linked with certain neurological diseases, such as Alzheimer’s disease and Huntington’s chorea. Injections of glutamate in laboratory animals have resulted in damage to nerve cells in the brain.
About 1.5 million metric tons of MSG were sold in 2001, with 4% annual growth expected. MSG is used commercially as a flavour enhancer. Once stereotypically associated with food in Chinese restaurants, it is now more often found in many of the most common food products consumed in the US:
- most canned soups of the US food industry like Campbell’s (except the low sodium varieties)
- most beef and chicken stocks of the US food industry like Swansons (except the low sodium varieties)
- most flavored potato chip products of the US food industry
- many other snack foods
- many frozen dinners
- almost all US-originated fast foods
- instant meals such as the seasoning mixtures for instant noodles.
In 1959, the FDA classified MSG as a “generally recognized as safe”, or GRAS, substance. In 1986, FDA’s Advisory Committee on Hypersensitivity to Food Constituents concluded that MSG poses no threat to the general public but that reactions of brief duration might occur in some people.
Because MSG is absorbed very quickly (unlike glutamic acid-containing proteins in foods), MSG could spike blood plasma levels of glutamate. Glutamic acid is in a class of chemicals known as excitotoxins, high levels of which have been shown in animal studies to cause damage to areas of the brain unprotected by the blood-brain barrier and that a variety of chronic diseases can arise out of this neurotoxicity.
Many scientists feel that primates are susceptible to excitotoxic damage and that humans concentrate excitotoxins in the blood more than other animals. Based on these findings, they feel that humans are approximately 5-6 times more susceptible to the effects of excitotoxins than rodents are. While they agree that typical use of MSG does not spike glutamic acid to extremely high levels in adults, they are particularly concerned with potential effects in infants and young children and the potential long-term neurodegenerative effects of small-to-moderate spikes on plasma excitotoxin levels.