Hi
@kaffirlime - yeah, I've been dealing with big insomnia issues too and I'm very sensitive to MSG as well. I now think there are 4 main parts to this insomnia: high cortisol at night, excitotoxins (excess glutamate, msg), GABA and serotonin. THe GABA and glutamate are related, it's a balancing act.
Cortisol: if possible, it's good to get an adrenal stress index test done. It's a saliva test which measures cortisol levels throughout the day/evening. If cortisol is elevated at night, it's almost impossible to sleep. Seriphos (phosphorylated serine, NOT phosphatidyl serine - they are 2 different things) was very helpful in normalizing high cortisol levels. I found it worked best taken in the morning; at night it worsened insomnia.
Excitotoxins: First, avoid MSG in all its forms. You're probably aware that anything that says "natural flavors" generally has msg or glutamate and you want to avoid it. I have found that almost all processed foods have "natural flavors" or other euphemism for MSG added (hydrolyzed yeast, etc.) You can find a list of these euphemisms on-line.
I do okay with say a can of chili at lunch, but don't dare eat it for dinner or I'll have severe insomnia.
These things help mop up excess glutamate in the brain: vitamin C (I take 2000 mg with each meal plus more at night - it's a high dose but I seem to need it); calcium pyruvate and resveratrol also help mop up excess glutamate. I take these at night before bed and in the middle of the night.
GABA: Niacin or niacinamide help sensitize or stimulate GABA receptors and can be very helpful for sleep. Do not get extended or time release niacin as it has been linked to liver damage. You need plain niacin, which causes flushing. I take it with l-theanine, it seems to be a good combo.
serotonin: I can't tolerate prescription anti-depressants but do well with 5-htp. It helps the brain produce serotonin without the awful side effects of ADs. I take 150 mg before bed though am going to be increasing it to 250 mg. It's a long story. Tryptophan can also help but is more expensive.
Glycine and inositol have also been helpful. I know, it's a ton of stuff to take. You'll have to experiment to see if any of this helps you. Good luck!
I also take 3 mg sublingual melatonin before bed and another 3 in the middle of the night.