No what I’m saying is maybe you are sensitive (for whatever reason - from a exceptional metabolism to placebo, over other sensitivities/allergies, complex psychological effects, etc everything is possible) but it’s certainly not because glutamate is a neurotransmitter.

Neurotransmitters and the stuff in our bloodstreams (nutrients, hormones and so on) are two very different systems. Think of it as a river and a power grid. We all have this massive stream of different molecules in our bodies, and we have an elaborate information system made from electric and chemical signaling, like cables and batteries, working right beside it. The batteries might happen to utilize the same molecules that swim around in the river, but they still have nothing to do with each other. The river doesn’t touch the batteries, and your body very carefully decides which part it takes out of the water and into the batteries. Highly simplified of course, but that’s kinda how you can imagine why one doesn’t hurt the other.

To add:

• No visible clocks. If possible don’t check the time at all while trying to sleep. Doing math at night (aka “oh no only 4 hours left”) only makes you angry or sad.
• No alcohol. If unavoidable, try to be sober by the time you want to fall asleep. (Dring sooner, if at all.)
• No coffee after midday. Some bodies suck at metabolising it.
• Bedroom should be as dark and silent and comfy as possible. If there’s any way you can add comfort, do it.
• For persisting sleep problems: Change position or location. (E.g. turn completely around in your bed, feet at the headrest, or sleep on the couch if comfortable.) Brains are very good at linking a location with a state of mind, and changing things around can help if the thought of your bed stresses you out already.

For severe problems it’s probably always wise to check with a physician, or if there’s specific stuff in your head that keeps you awake to consider telling a friend or therapist about it. To distance yourself from your thoughts is something everybody can learn and it can be tremendously helpful with stuff like that.

Even though you’re right in that glutamate is a neurotransmitter, eating it doesn’t affect our brain chemistry at all. It can’t pass the blood-brain-barrier. Which is relieving since basically every food group contains it and flooding our brain with that would lead to violent epileptic seizures and certain death. Not insomnia.

And melatonin isn’t a neurotransmitter but a hormone.

So maybe you do in fact sleep better when avoiding specific food groups in the evening, but your explanation certainly isn’t correct.

Just putting this out there since glutamate is such a highly misunderstood molecule surrounded by many misconceptions, this one being a very common one.