MSG is a preservative I think. It is supposedly like salt or something that enhances flavor. It's in many processed foods like chips.
This is from Wikipedia
Health concerns
Main article: Glutamic acid (flavor)#Research into health effects
MSG as a food ingredient has been the subject of scientifically unsubstantiated health concerns. A report from the Federation of American Societies for Experimental Biology (FASEB) compiled in 1995 on behalf of the FDA concluded that MSG was safe for most people when "eaten at customary levels." However, it also said that, based on anecdotal reports, some people may have an MSG intolerance which causes "MSG symptom complex"—commonly referred to as Chinese restaurant syndrome—and/or a worsening of asthmatic symptoms.[7] Subsequent research found that while large doses of MSG given without food may elicit more symptoms than a placebo in individuals who believe that they react adversely to MSG, the frequency of the responses was low and the responses reported were inconsistent, not reproducible, and were not observed when MSG was given with food.[8] While many people believe that MSG is the cause of these symptoms, a statistical association has never been demonstrated under controlled conditions, even in studies with people who were convinced that they were sensitive to it.[9][10][8][11] Adequately controlling for experimental bias includes a placebo-controlled double-blinded experimental design and the application in capsules because of the strong and unique after-taste of glutamates.[9]
[edit] United States
Monosodium glutamate is one of several forms of glutamic acid found in foods, in large part because glutamic acid is pervasive in nature, being an amino acid. Glutamic acid and its salts can also be present in a wide variety of other additives, including hydrolyzed vegetable proteins, autolyzed yeast, hydrolyzed yeast, yeast extract, soy extracts, and protein isolate, any one of which may appear as "spices" or "natural flavorings." The food additives disodium inosinate and disodium guanylate are usually used along with monosodium glutamate-containing ingredients, and provide a likely indicator of the presence of monosodium glutamate in a product. For this reason, the FDA considers labels such as "No MSG" or "No Added MSG" to be misleading if the food contains ingredients that are sources of free glutamate, such as hydrolyzed protein.[12]
In 1993, the FDA proposed adding the phrase "(contains glutamate)" to the common or usual names of certain protein hydrolysates that contain substantial amounts of glutamate.[12]
[edit] Asia