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.