MSG (Monosodium glutamate) stimulates specific receptors located in taste buds which induce the taste known as umami, one of the five basic tastes.
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.
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 (glutamate is the anionic form of glutamic acid, a naturally occurring amino acid).
Issues surrounding these health implications of MSG consumption are the subject of much debate. A considerable body of anecdotal evidence exists suggesting negative health effects, but this has not yet been supported by recognised research. MSG has been shown to cause obesity in lab rats. Animal research compels some researchers to theorize that MSG has a role in the so-called "obesity epidemic". Though a similar effect has never been observed in humans, you would not know that from looking around in this office.