MSG is used commercially as a flavour enhancer and is (stereotypically) associated with food in Chinese restaurants.
MSG is a salt of glutamic acid, one of the amino-acid building blocks of
protein. Many foods naturally contain free glutamates - these include
fresh tomatoes, tomato paste and Parmesan cheese. In the traditional
cuisine of east Asia, glutamate-rich foods such as seaweeds and
mushrooms have long been used to add a deep savory flavor to soups and
Purified, crystalline MSG became available in 1909 and was patented and
marketed by a Japanese company. Shortly thereafter, Asian cooks began to
add it to their dishes. Glutamic acid and its salts, including MSG,
stimulate a particular taste receptor, the one responsible for the
so-called "fifth taste" (in addition to sweet, sour, salty, and
bitter). The official name for the receptor and taste is umami, a
Japanese word meaning "meaty" or "savory." The company that patented
MSG almost a century ago, Aji-No-Moto ("essence of taste"), built its
fortune on this compound. Aji-No-Moto-USA was established in 1958, when
pure MSG appeared in groceries here under the catchy brand name,
Extensive scientific research suggests MSG causes obesity in lab rats.
This compels me to theorize that MSG plays a role in the "obesity
epidemic" witnessed here at Digital Militia HQ.