MSG, is added to food to increase its shelf life "preserve" it both before and after it is prepared. It also enhances flavor.
MSG is linked to high blood pressure (although not much research has been done to support this), it can make dry mouth worse similar to too much salt intake and is linked to migraine headaches.

MSG is also found on food labels as, "Hydrolized vegetable and/or animal protien." Even if MSG, or monosodium glutamate is not listed as an ingredient if one of the above is on the label you can be sure it is MSG.

Hope this helps.

Cheers,

Mike