The interaction of reactive oxygen species with DNA and RNA produces oxidation products of these base rings. DNA repair enzymes must remove the damaged bases in order to maintain viability. Oxidation of guanosine produces 8-hydroxy-2′-deoxyguanosine (8OHdG). The concentration of 8OHdG in urine has been shown to be an accurate measure of the rate of polynucleotide oxidative damage. Elevated 8OHdG is a sign that antioxidant nutrient intake may need to be increased. Toxicants and lifestyle stress factors may contribute to increased oxidative challenge.