**6. Dietary factors and OGG1 polymorphism**

Interestingly, Sørensen et al. reported that the effect of vegetable consumption was associated with the *OGG1* Ser326Cys polymorphism [58]. A non-synonymous (associated with an amino acid change) genetic polymorphism at codon 326, Ser326Cys, in the *OGG1* gene is a strong candidate as a genetic factor for cancer risk [59, 60]. In fact, the OGG1 Ser326Cys enzyme exhibited functional defects [61]. OGG1 Ser326Cys excised 8-oxo-Gua from duplex DNA and cleaved abasic sites at rates 2- to 6-fold lower than those of the wildtype enzyme. Yamane et al. reported that 8-oxo-Gua-induced mutations were more efficiently suppressed in OGG1-Ser326 transduced cells than OGG1-Cys326 transduced cells, suggesting that OGG1-Cys326 has reduced ability to prevent mutagenesis by 8-oxo-Gua than OGG1-Ser326 *in vivo* in human cells [62]. Sørensen et al. observed a 54% decrease in lung cancer risk per 50% increase in vegetable intake among homozygous Cys326Cys carriers, and no decrease in risk among carriers of Ser326Ser or Ser326Cys. Therefore, to evaluate the effect of food factors on carcinogenesis, the OGG1 polymorphism should be considered.
