Logical Reasoning -
Processed Free Glutamic Acid (P-FGA for this article) is a processed building block of all protein (not in naturally occuring form).
Amino acids are essential to the creation of not only proteins (tissue) but hormones and enzymes as well in the human body
My theory is -
Many, if not all intolerances and allergies could be the result of abnormally created tissues, hormones, enzymes, etc..., which rely on amino acids to be "built" in a certain way for proper function, which they aren't built properly because of the constant ingested supply of P-FGA's. When P-FGA is ingested as the body is attempting to undergo a certain change (created by any stress factor, internal and/or external), the processed building block is used to adapt to this change and thus creates abnormal cellular tissue, hormones, enzymes, etc... This is not a far stretch of the imagination considering P-FGA's exist is nearly 90% of the American food supply.
The reasoning behind this theory is that we all know when the body undergoes stress it attempts to adapt to the stress factors to overcome it. Athletes, Bodybuilders, and anyone athletic enough knows this simply as "getting results". The body becomes "efficient" at performing a certain action if given the same repeated action over time because it adapts to the action, a.k.a. stress factor. This efficiency adaptation is also known as the "Plateau" in body building terms. Logically, if the body were to receive a constant supply of a processed or altered building block of the very substance that is used to adapt to the stress factor, abnormal side effects will occur because the actual tissue, hormone, enzyme, etc... created can't function as it should.
A developmental test has been done already some decades ago by a prestigious dentist, testing the growth patterns of teeth and the jaw structure of people who consume processed food vs. unprocessed raw foods in countries American's would consider primitive &/or 3rd world due to the lack of technology as we know it (Documentary: The Beautiful Truth).
Keep in mind this is a theory, however I believe it has some value as it's logical and reasonable and should be tested by an avid researcher/scientist who's knowledgeable on the matter. Thoughts?