MSG is a flavor enhancer which has been used effectively for nearly a century to bring out the best flavor of foods.
Its principal component is an amino acid called glutamic acid or glutamate. Glutamate is found naturally in protein-containing foods such as meat, vegetables, poultry and milk. The human body also produces glutamate naturally in large amounts. The muscles, brain and other body organs contain about four pounds of glutamate, and human milk is rich in glutamate, compared to cow's milk, for example.
Glutamate is found in two forms: "bound" glutamate (linked to other amino acids forming a protein molecule) and "free" glutamate (not linked to protein). Only free glutamate is effective in enhancing the flavor of food. Foods often used for their flavoring qualities, such as tomatoes and mushrooms, have high levels of naturally occurring free glutamate.
The glutamate added to foods for flavor in the form of MSG represents only a small fraction of the total amount of glutamate consumed in the average daily diet. The average person consumes around 10 grams of bound glutamate and up to one gram of free glutamate daily. The human body creates about 50 grams of free glutamate daily. In contrast, the added intake of free glutamate through MSG amounts to approximately one-half gram per person, or 1/10 teaspoon, daily.
But some say its toxic, others say its safe, and on and on.
This is a good website to check things out
http://www.msgfacts.net/
Source:
http://answers.yahoo.com/question/index?qid=20090202114757AASvopC
