The onset of PD may not be directly related to Hcy or B vitamins [11,12,13]; however, the anti-parkinsonian drug levodopa, which is converted into dopamine in the brain, undergoes partial deactivation by methylation via catechol-O-methyltransferase (COMT) and increases plasma total Hcy levels [14]. This evidence concerns the gene COMT and Parkinson disease.