Is manufactured MSG a problem?

According to some MSG opponents the glutamate added to foods is “bad” and the natural glutamate in our bodies is “good”.  MSG sellers argue that MSG is exactly like the glutamate in the human body, therefore it must always be “good”.  It is not so simple.  There are contaminants in processed MSG.  An analogy that can be used is that there are right-handed amino acids and left handed ones.  They are like mirror images of each other.   Processed MSG contains not only the kind of amino acids the body is used to handling, but mirror image ones too.  This may cause problems because it is like putting the wrong glove on your hand.  It’s not quite the same.  We don’t exactly know what problems this may cause.  On the other hand (so to speak) the fact that glutamate the body is used to handling is also in MSG may present a problem because an excess of naturally occurring glutamate is well known by neuroscientists to be a problem in many disease states.  Natural glutamate can cause problems we already know about.  The reason food processors “free” glutamate from its bound form, is that it acts as a neurotransmitter in its free form.  The food industry’s claim that free glutamate is as harmless as bound glutamate is disingenuous at best.  If it was exactly the same, they wouldn’t need to hydrolysed vegetable protein (split the amino acids apart).