The present invention relates to methods for monitoring serum glutamate levels in a mammal, particularly in a human. The methods are useful to quantify the ability of the mammal to metabolize dietary glutamate as a diagnostic marker for predicting the onset of or propensity for developing a central nervous system (CNS), psychotic, or related disorder, associated with glutamate toxicity. The methods are also useful for designing regimens for modulating serum glutamate levels in a mammal to treat or prevent such a disorder.本發明涉及監測哺乳動物,特別是人類,體中的血清麩胺酸鹽水平的方法。該方法有助於量化哺乳動物代謝膳食中麩胺酸鹽的能力,以作為預測與麩胺酸鹽毒性相關的中樞神經系統(CNS)、精神病,或相關疾病的發作或傾向的診斷標記物。該方法亦有助於設計用於調節哺乳動物體內的血清麩胺酸鹽水平的方案,以治療或預防這種疾病。