MSG- Mono Sodium Glutamate. Glutamate being Glutamic Acid, a non-essential amino acid. Non-essential meaning your body produces it naturally. That’s right, glutamates are in your body right now! Mono-sodium meaning it is bound to sodium rather than protein or say potassium.
Glutamic Acid is a neurotransmitter. You need it for your brain to work. Without it, you’ll die.
Now being non-essential, it is true you do not need to consume it, like you would say tryptophan. However, being an amino acid, which are the building blocks of protein, glutamic acid must exist in a lot of food right? Well yes it does, and plenty of it! Tomatoes, Cheese, Meats, Fish, Algae, Soy, all of those contain good old glutamic acid, aka MSG. You are consuming MSG whenever you eat any of the these foods!
To make MSG, you basically just must isolate glutamic acid, then add sodium. This was originally done in the late 1900’s by the Japanese from seaweed in order to purify the “umami” flavor. They would dehydrate seaweed and being high in glutamic acid and sodium, MSG would form crystals on the top. Today, we use more modern and efficient means through bacterial fermentation.
Now that whole “Chinese Restaurant Syndrome”(CRS) thing. First things first, it doesn’t exist. In 1968 Robert Ho Man Kwok reported feelings of “numbness at the back of the neck, gradually radiating to both arms and the back, general weakness and palpitations.” This occurred after he ate a Chinese-American meal and blamed the culprit MSG. Thus CRS was born.
Ever since then, CRS has scared millions of Americans though the medias portrayal of MSG and CRS. Now you will see almost every single Asian restaurant with a “no MSG” sign on their establishment or Menu.
The fact of the matter is, and regardless of what you have heard, there is no proof(read: none, zip, zilch) that MSG causes CRS or any other symptom. An exception would be if you consume ridiculous quantities, i.e. several ounces(which would taste unpalatable!). In fact it is far less toxic than salt(5 times less!, 15-18g/kg vs 3g/kg), its cousin in seasoning. Again, there has been several double blind studies proving that not only did CRS not exist, but so called “MSG sensitivity/allergy(Fun fact: If someone ever says they have an allergy to MSG, you’re talking to a ghost because they are died)” didn’t exist.
Conclusion/TL;DR: MSG is not even remotely dangerous to humans.