Nicotine [3-(1-methyl-2-pyrrolidinyl)-pyridine] is a major alkaloid in tobacco products and has proven to be a potential genotoxic compound. Many natural dietary products can suppress the DNA adduction, and hence act as inhibitors of cancer. In this study, we investigated the inhibitory effects of curcumin, garlic squeeze, grapeseed extract, tea polyphenols, vitamin C, and vitamin E on nicotine-DNA adduction in vivo using an ultrasensitive method of accelerator mass spectrometry (AMS). The results demonstrated that all the dietary constituents induced marked dose-dependent decrease in nicotine-DNA adducts as compared with the control. The reduction rate reached about 50% for all agents, except garlic squeeze (40%), even at its highest dose level. Amongst the six agents, grapeseed extract exhibited the strongest inhibition to the DNA adduct formation. Therefore, we may arrive at a point that these dietary constituents are beneficial to prevent the harmful adduct formation, and thus to block the potential carcinogenesis induced by nicotine.