Is monosodium glutamate vegetarian-compatible?

What to know about monosodium glutamate

Monosodium glutamate is the sodium salt of glutamic acid, and our data grades it E for free glutamate: the one trigger it genuinely carries. Everything else is clean, with A grades for gluten, lactose, FODMAPs, salicylates, sulfites and nickel, and only a B for histamine. The important context is that the glutamate in MSG is the same molecule as the free glutamate already present in parmesan, ripe tomatoes, mushrooms, kombu and soy sauce, so a body cannot tell the two apart. The reputation MSG carries comes from a 1968 letter to a medical journal that coined "Chinese restaurant syndrome", and the panic that followed said more about who was cooking than about the chemistry. Decades of double blind, placebo controlled testing have largely failed to reproduce symptoms reliably, and where responses do appear they cluster at very large doses taken on an empty stomach without food. That is not the same as saying nobody reacts. Some people consistently report headache, flushing or tightness after glutamate heavy meals, and glutamate sensitivity is real enough that we grade it. The honest answer is that MSG is one of the easiest triggers to test rather than assume: log the meals that contain it, log the parmesan and tomato heavy meals that carry just as much free glutamate, and see whether your symptoms follow the glutamate or follow something else entirely.