WHY AT LEAST 68% OF U.S. POPULATION ARE VULNERABLE TO MSG TOXICITY?

Glutamate act as the most abundant neurotransmitter in brain. but, as it is an excitatory neurotransmitter, it's extracellular concentration (glutamate concentration outside the brain cells) are very tightly controlled. The main regulatory mechanism involves astrocytes (the star shaped cell in the diagram), which can convert GLU (Glutamate) to GLN (glutamine) and then release GLN to extracellular space. Then glutamatergic neurons capture these GLN molecules and convert them back to GLU, which is now released into synaptic space where GLU exerts it's function as a neurotransmitter. As soon as neural message is transmitted, GLU molecules are efficiently recycled by astrocytes.







What happen if this mechanism fails (for an example, in a chronic high dose exposure to MSG) ? Then excitatory (means it can fire neurons - neuron firing is exactly needed to neural message transmission, but if this happens out of control, the neurons would die) GLU pile up at synaptic space. They act on GLU receptors.

There are two major types of GLU receptors: ionotropic and G protein coupled receptors. Ionotropic receptors are of three sub types; NMDA, AMPA and Kainate. Out of these, NMDA and AMPA receptors are often co located, while Kainate receptor distribution in brain is limited to few specific areas. Basically, these ionotropic type of receptors dominate in cortex, basal ganglia and sensory pathways. Just, take a look at the below diagram of a NMDA recptor.



It is an ion gated calcium channel. When GLU act on Glu/NMDA site, the channel opens allowing calcium passage from outside to cell interior. Calcium is an key element helping in neural message transport, but if this passage is not tightly controlled, a massive calcium flux occur. Such a high amount of calcium ions in a nerve cell can practically induce cell excitation (or neural firing) until death.

Do you see Zn and Mg in above diagram? Both acts to block the channel, hence are very important to body in regulating this useful, but dangerous channel. out of these two Zn blockage is potent than the one produced by Mg. So, by now you should be clear that Zn and Mg are essential elements to prevent MSG induced cell death.

Now, look at following figure that was from official U.S. database.



It clearly shows, 68% or more than two thirds of U.S. population are Magnesium deficient and 42% of people are Zinc deficient. As both these elements are needed to maintain fine regulation of above calcium channel, these very individuals are vulnerable to MSG induced neuronal damage, depending on their dietary habits.

Sources:

1. Traynelis, S. F., Wollmuth, L. P., McBain, C. J., Menniti, F. S., Vance, K. M., Ogden, K. K., … Dingledine, R. (2010). Glutamate Receptor Ion Channels: Structure, Regulation, and Function. Pharmacological Reviews, 62(3), 405–496. http://doi.org/10.1124/pr.109.002451

2. https://www.nal.usda.gov/fnic/vitamins-and-minerals