The quote from the Smithsonian Mag article -- "Glutamates that occur naturally in food come intertwined with different chemicals or fiber, which the body is naturally inclined to regulate" -- is by Amy Cheng Vollmer (http://www.swarthmore.edu/academics/biology/faculty-and-staf...), professor of biology at Swarthmore College.

Some of the first evidence that glutamate additives were dangerous was provided by Dr. John W. Olney in 1969:

"Brain Lesions, Obesity, and Other Disturbances in Mice Treated with Monosodium Glutamate" (http://www.sciencemag.org/content/164/3880/719).

Dr. Olney and Harvard scientist Dr. Jean Mayer (https://en.wikipedia.org/wiki/Jean_Mayer) independently came to the same conclusion and led to the food industry removing MSG from baby food (and later all the MSG variants) because a baby's blood-brain barrier isn't fully developed so it can't protect against increased glutamate consumption:

The Harvard Crimson: Baby Food Manufacturers Will Suspend Use of MSG (http://www.thecrimson.com/article/1969/10/27/baby-food-manuf...)

There is plenty of recent research that shows glutamate's effects on the brain...

* Serum proteins bypass the blood-brain fluid barriers for extracellular entry to the central nervous system (http://www.ncbi.nlm.nih.gov/pubmed/8491281)

* Excitatory Amino Acids in Neurologic Disorders
(http://www.nejm.org/doi/full/10.1056/NEJM199407283310414)

* Dana Foundation: Protecting the Brain from a Glutamate Storm (http://www.dana.org/news/cerebrum/detail.aspx?id=7376)

However, one of the most interesting reports is the government's 1995 Life Sciences Research Office (LSRO) of the Federation of American Societies for Experimental Biology (FASEB) report: "Analysis of Adverse Reactions to Monosodium Glutamate (MSG)".

The full FASEB 293 page report is not available online in digital form (http://books.google.com/books/about/Analysis_of_adverse_reac...). You can order a copy from the LSRO FASEB (http://www.gpo.gov/fdsys/granule/FR-1995-10-03/95-24594/cont...), and there are a few used copies on Amazon (http://www.amazon.com/Analysis-Adverse-Reactions-Monosodium-...).

Here are a few statements from the report (I'll write up a more detailed blog post of my notes on this later):

* Page 29: "The net result is that certain areas of the brain may be vulnerable to acute, large, magnitude fluctuations in plasma glutamate concentrations because flooding from adjacent circumentrical organs."

* Page 42: "Levels of ingested MSG might be sufficient to raise the concentration of blood glutumate and related compounds enough to change the levels of these amino acids in the brain, particularly in the circumvention areas not protected by the blood-brain barrier."

* Page 42-43 (regarding the Pineal gland): "The elevated levels of glutumate and related compounds would have adverse neuroexcitatory effects, be neurotoxic, and/or initiate a chain of metabolic events that would result in either neurotoxicity or the release of substances that would cause the neurological manifestations reportedly associated with MSG exposure."

* Page 46: "It is conceivable that the consumption of MSG in genetically or otherwise predisposed individuals can exacerbate a preexisting neurological condition."

* Page 100: "In contrast, glutumate concentrations in the extracellular fluid in brain regions not protected by the blood-brain barrier will closely mirror changes in circulating glutumate concentrations."

* Page 103: "Theoretically, if blood levels seen in animals as a result of MSG challenge were achived in humans, similar lesions and/or neuroendocrine effects would be expected to occur."

* See pages 28, 29, 43-48, 96, 100, and 104 for citations that the blood-brain barrier can be breached at several sites in the normal brain.