The mechanism of the observed diet-evoked changes in the CYP2D enzyme expression and activity in the liver has not been investigated as yet; however, abnormal diets are known to induce epigenetic mechanisms (such as DNA methylation, histone modification, and miRNA effect), which affect gene expression or protein stability and lead to metabolic diseases including hepatocellular carcinoma [12,36]. The gene discussed is CYP2D6; the disease is metabolic disease.