Among individuals aged younger than 65 years with the Ca:Mg intake ratios equal to or over 2.6, reducing Ca:Mg ratios to around 2.3 increased 5-mC modifications (i.e. cg16371860) and reduced 5-hmC modifications (i.e. cg26337277) in the TMPRSS2 gene. These findings, if confirmed, provide another mechanism for the role of Mg intervention for the prevention of COVID-19 and treatment of early and mild disease by modifying the phenotype of the TMPRSS2 genotype.