Oxidative DNA damage is induced by chronic cigarette smoking, but repaired by abstention

The association of chronic cigarette smoking and abstention with oxidative DNA damage was studied. The serum level of an oxidative DNA damage marker, 8-hydroxy-2'-deoxyguanosine (8-OHdG), was measured in 20 healthy male smokers and 8 healthy male non-smokers. The 8-OHdG level was significantly higher in the smokers than in the non-smokers (0.22 +/- 0.05 vs. 0.07 +/- 0.02 ng/ml, p < 0.001). Ten of 20 smokers abstained from smoking for 4 weeks. Their 8-OHdG levels were significantly reduced by the smoking abstention (0.27 +/- 0.05 to 0.14 +/- 0.02 ng/ml, p < 0.001). The remaining 10 not only abstained from smoking, but also received 2 g/day of oral vitamin C. Their 8-OHdG levels were also significantly reduced (0.27 +/- 0.05 to 0.13 +/- 0.02 ng/ml, p < 0.001). However, there was no significant difference in the serial changes in 8-OHdG level between the smoking abstention group and the smoking abstention with vitamin C supplementation group. These results suggest that chronic cigarette smoking enhanced oxidative DNA damage, but the damage was repaired by smoking abstention, and that vitamin C supplementation might not enhance the repair. In light of the DNA damage, smoking abstention should be encouraged.