Monosodium GlutamateMonosodium glutamate, often referred to as MSG, is a common flavor-enhancing additive in contemporary foods. The Japanese were the first to discover the compound’s unique flavorful property in 19081, but it did not reach American consumers until the middle of the 20th century, when the white powder was added en masse to (American) Chinese food. It is now ubiquitous in highly-processed cuisine, like ramen noodles, soup, and fast food.

One can isolate the chemical MSG from the fermentation of starches, molasses, sugar cane, or sugar beets. In solution, the Na+ ion will freely dissociate from the terminal carbonyl, rendering the functional substance glutamate. Glutamate is a non-essential amino acid, meaning that most humans need not obtain the compound exogenously; they can produce it themselves. As an amino acid, glutamate occurs naturally in protein-rich foods such as meats and dairy products, especially Parmesan cheese.2 Moreover, although it is not an additive, glutamate is a common component of soy sauce and Worcestershire sauce, arising from the fermentation processes used in their production. Although food producers are required to specifically indicate if monosodium glutamate is an ingredient, free glutamate may also appear under the less-assuming titles of “hydrolyzed soy protein” and “autolyzed yeast.”

The four classic tastes are sweet, salty, sour, and bitter. Enter umami, the fifth taste. In fact, “umami” is not exactly a taste, but more a general sensation of savoriness and vague satisfaction (”umami” means “savory” in Japanese). The umami receptor on the tongue — a G-protein-coupled receptor named T1R1+3 — binds selectively to L-glutamate and L-aspartate (another amino acid with a similar structure to glutamate).3 The “L” of L-glutamate indicates that only MSG in the levorotatory form will activate the umami receptor. All that means is that MSG can assume two chiral forms - D and L, but only one of them brings on the pleasance. As such, the additive MSG typically contains a higher ratio of L:D than naturally occurring glutamate-containing compounds.4

So, what of MSG? Of course, any chemical that makes people unnaturally satiated is reason for skepticism … and monodsodium glutamate is no exception:

IN 1968 a Chinese-American physician wrote a rather lighthearted letter to The New England Journal of Medicine. He had experienced numbness, palpitations and weakness after eating in Chinese restaurants in the United States, and wondered whether the monosodium glutamate used by cooks here (and then rarely used by cooks in China) might be to blame.5

What followed was a huge backlash of anti-MSG sentiment; a stigma that, although faded, has never disappeared. A new term was coined: “Chinese restaurant syndrome,” a.k.a. “monosodium glutamate symptom complex.” As the physician noted in his letter, MSG can elicit mild reactions in some individuals, which may include

  • “Headache, sometimes called MSG headache
  • Flushing
  • Sweating
  • Sense of facial pressure or tightness
  • Numbness, tingling or burning in or around the mouth
  • Rapid, fluttering heartbeats (heart palpitations)
  • Chest pain
  • Shortness of breath
  • Nausea
  • Weakness”6

Glutamate is a neurotransmitter with known links to exitotoxicity.7 At the time, there were rumors that MSG could cause/exacerbate brain lesions, Alzheimer’s disease, Huntington’s chorea, and amyotrophic lateral sclerosis. After being commissioned by the FDA, the Federation of American Societies for Experimental Biology (FASEB) released a conclusive report in 1995 that demonstrated no long-term effects from moderate consumption of MSG, although they did find that some people suffer the short-term repercussions previously listed. “In otherwise healthy MSG-intolerant people, the MSG symptom complex tends to occur within one hour after eating 3 grams or more of MSG on an empty stomach or without other food. A typical serving of glutamate-treated food contains less than 0.5 grams of MSG. A reaction is most likely if the MSG is eaten in a large quantity or in a liquid, such as a clear soup.”2 The study also found no discernible difference in the symptomatic effects of derived glutamate and naturally-occuring glutamate. A subsequent study in 1997 reproduced the FASEB finding that MSG-intolerant persons experience mild reactions to the chemical.8 However, no study has ever demonstrated a link between MSG and serious, long-term illness.

While you should not make ramen noodles a food group in your daily diet (the extreme sodium content is reason enough9), a little monosodium glutamate is probably all right. Yum(ami).

Further Reading:
(1) Encyclopaedia Britannica.
(2) U.S. Food and Drug Administration. 1995.
(3) The Receptors for Mammalian Sweet and Umami Taste. Cell. 2003.
(4) Evaluation of free D-glutamate in processed foods. Chirality. 1994.
(5) Yes, MSG, the Secret Behind the Savor. New York Times. 2008.
(6) Mayo Clinic. 2008.
(7) Delayed increase of Ca2+ influx elicited by glutamate: role in neuronal death. Molecular Pharmacology. 1989.
(8) The monosodium glutamate symptom complex:next term Assessment in a double-blind, placebo-controlled, randomized study. Journal of Allergy and Clinical Immunology. 1997.
(9) Ramen noodle nutrition facts.
(10) Safety Assessment Report on MSG from Food Standards Australia/New Zealand. 2003.