Both magnesium and zinc function in stabilizing the receptor in the brain that glutamate hits on (NMDA).

I've read that taking branched chain amino acids (often available as a bodybuilding supplement) can increase the rate at which glutamate is metabolized to something else.

Finally, alcohol will blunt the response to an excess of glutamate from a meal. This, however, is not a long-term solution, because the brain will adjust for this effect.