Although there is no evidence that human gut microbiota can produce BMAA, a study has reported that hypermethylation in the promoter region of the SLC7A11 gene in patients with PD is link to downregulation of the cysteine-glutamate antiporter, a target of BMAA, which is thought to be consistent with environmental risks related to PD [142]. The gene discussed is SLC7A11; the disease is Parkinson disease.