MSG is Monosodium Glutamate, a sodium salt of glutamic acid (an amino acid). It was traditionally extracted from seaweed in Asian cultures, but is now mostly manufactured from the fermentation of sugars. Like regular table salt, MSG is a flavor enhancer and preservative.
Also like regular table salt, MSG is a source of sodium. High sodium intake is linked to hypertension and high blood pressure, heart disease, fluid retention (edema) and kidney stones. But MSG is like salt’s wicked stepsister. There is evidence of MSG causing retinal degeneration, brain cell death (leading to behavioral disorders and learning disabilities), reproductive problems, obesity, irritable bowel, heart irregularities, asthma, and migraine headaches.
To be fair, most evidence of MSG’s negative health effects is anecdotal or the product of small-scale research. There have been no major investigations into the effects of MSG to date. Advocates say that studies are not needed because it is not dangerous. Opponents say that major studies are being prevented by the food industry because MSG is so widely used. You decide who you want to listen to.
By the way, in researching your question I found out that MSG can be hidden on food labels in a lot of different ways. Its aliases include: autolyzed yeast (extract), sodium caseinate, calcium caseinate, carrageenan, any kind of hydrolyzed protein, any kind of protein isolate, modified food starch, textured protein, and yeast extract. What’s even better is that any or all of these can be listed on a food label simply as “spices” or “natural flavorings.”
Insert evil cackle here.