MSG is the sodium salt of glutamic acid, one of the most common amino acids found in nature.
 Glutamic acid is produced abundantly in our bodies and is found in many foods we eat every day, including meat, fish, eggs and dairy products, as well as tomatoes, corn and nuts. When a protein containing glutamic acid is broken down, for example through fermentation, it becomes glutamate.
 Glutamate activates our taste receptors, causing a delicious savory taste known as umami.