Compounds containing nucleic acid bases or their precursors modified by enrichment at specific sites with heavy stable isotopes of elements naturally present at those sites in minute amount are useful for the treatment of diseases characterized by altered gene expression and altered pattern of epigenomic control. These compounds, when used as nutrients or in other medicinal application methods, can alter the DNA methylation pattern in a simple way through the well-understood mechanism of kinetic isotope effect (KIE). This effect could also be useful for modifying methylation kinetics in stem cell technology, cloning and as disease therapeutics.