COMT and Parkinson disease: Zhu [132] suggests that in addition to vitamin C, other antioxidants are important in the diet for the reduction of the risk of PD, such as vitamins B6 and B12, S-adenosyl-L-methionine (SAME), and folic acid, based on the regulation of catechol-O-methyltransferase (COMT), an enzyme that acts in catecholamine degradation.