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Comment by 1MachineElf | Hacker News Reader

Glutamate can act as an excitotoxin. Excitotoxicity is believed to be associated with neurodegenerative diseases.

https://www.frontiersin.org/articles/10.3389/fnins.2015.0046...

https://www.frontiersin.org/articles/10.3389/fncel.2020.0005...

Related- conflicting research findings and anecdotes on glutamate toxicity from MSG consumption might indicate certain people are more susceptible to the negative effect than others. Raising this question often invites comments on: whether or not cautioning against MSG is actually racist; misdirection about the sodium being the prime issue with MSG; and comments from those with vested interest in MSG (MSG producers, any food producer with MSG, Yeast Extract, or "Natural Flavorings" in their ingredients list, etc.)

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from the first link:

>L-glu along with glutamine is the most abundant free amino acid in the central nervous system

this would suggest that L-glu is highly regulated in the body. Abundance usually means there should be storage of it if level swings can bring "inbalance" to it's usage.

on top of that, from this study: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3698427/

>In the brain, Glu, which is locally produced completely de novo from glucose, acts as a major excitatory neurotransmitter, and its activity regulates synaptic plasticity, learning, memory, motor activity, and neural development. But dietary Glu is almost impermeable into the circulating blood. Also there is the blood–brain barrier against Glu in between blood and brain so as to not to incorporate into it the brain.

if high MSG(or just G from other sources) consumption did cause neurodegenerative diseases, shouldn't we see that data clearly in places that consume more in culture?

I think there are two possible explanations for the disparity.

1) Genetics.

2) A leaky blood-brain barrier (which could also be influenced by genetics.) Multiple studies have shown a link between leaky a blood-brain barrier and the same neurodegenerative diseases that increased levels of glutamate are linked to. Things as simple as high blood sugar can contribute to a leaky blood-brain barrier, so it could be more common than we imagine. Tests are difficult to administer, so it's hard to estimate how common degrees of blood-brain barrier leakage are in populations.

if high MSG(or just G from other sources) consumption did cause neurodegenerative diseases, shouldn't we see that data clearly in places that consume more in culture?

If anything, the correlation seems to be negative.

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