Glutamate is the major excitatory neurotransmitter in the brain, and its regulation is abnormal in schizophrenia: glutamate levels are too low at some receptors, and too high at others. As well, free radicals surrounding glutamate receptors also interfere with their proper function. N-acetylcystine (NAC) is a safe and widely-available dietary supplement that may restore glutamate to its correct levels in the brain, and may also help protect the brain from antioxidant damage.