This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Over the holidays my husband has been experimenting with Japanese cooking, and as various broths simmered on the stove and our collection of soy-based pastes and sauces expanded, my love affair with MSG was rekindled. MSG (monosodium glutamate) is the sodium salt of glutamic acid, a naturally occurring amino acid that makes up proteins. Glutamic acid was identified in 1908 by Kikunae Ikeda as the molecule responsible for the deliciousness of dashi, a stock made from simmered seaweed and fermented fish that is the base for many Japanese dishes. Dashi isn't sweet, sour, salty, or bitter--the four tastes known before Professor Ikeda's experiments--but it has a difficult to describe fifth taste that Ikeda called umami, which is Japanese for "delicious." Umami adds savoriness to many dishes and "It stimulate[s] all surfaces of the tongue and oral cavity, producing a slight sensation of 'furriness' on the tongue, and a mild but lasting aftertaste." Glutamic acid is present in high concentrations in many delicious foods and sauces, from veal stock to yeast extract to tomatoes and parmesan cheese. After experimenting with many different salts of glutamic acid, commercial production of MSG as an external flavor additive began in 1909 and was marketed as AJI-NO-MOTO, meaning "the essence of taste."
Sixty years later, the world of delicious cooking was thrown into chaos after a letter to the editor in The New England Journal of Medicine by the Chinese-American doctor Robert Ho Man Kwok suggested a possible link between MSG and a set of symptoms he had experienced after eating at American Chinese restaurants including numbness, weakness, and palpitation. Though he suggested many other possible causes for the symptoms and hoped that more research would be done, the journal titled the letter "Chinese-Restaurant Syndrome" and a media-fueled anti-MSG frenzy was born. Many double-blind, placebo-controlled experiments later, no reproducible link has been found between MSG and any symptoms or negative health effects, but the stigma remains and even high-glutamic acid foods like miso paste are often misleadingly advertised as "No MSG added."
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MSG is an interesting molecule, the key to many tasty dishes and a case study for our complicated relationship with food science. I wish everyone a happy and delicious 2012, where the food is flavorful and correlation is never mistaken for causation!