Plasma levels and redox status of ascorbic acid and levels of lipid peroxidation products in active and passive smokers

Both active and passive smoking are regarded as risk factors for various di seases. To clarify the effects of active and passive smoking on plasma vita min C levels and lipid peroxidation status, we examined the plasma levels o f ascorbic acid (AA), its redox status [ratio of dehydroascorbate (DHAA) to total AA], the levels of thiobarbiturate reactive substance (TBARS), and t he levels of Lipid peroxides (LPO) in smokers, nonsmokers, and nonsmokers r egularly exposed to environmental cigarette smoke (passive smokers). The st udy population consisted of 149 healthy males: 75 active smokers (consumpti on of > 15 cigarettes/day for more than 5 years), 36 passive smokers (more than 10 hr/week exposure to environmental cigarette smoke), and 38 nonsmoke rs (no cigarette smoke exposure). There were no significant differences in plasma TEARS and LPO levels among the three groups. Plasma levels of AA, th e reduced form of vitamin C, were significantly lower in active smokers tha n in the combined nonsmoking groups (7.2 +/- 3.5 and 8.4 +/- 3.4 mu g/mL, r espectively; p < 0.05). Although no significant differences were found in p lasma DHAA levels among the three groups, the ratios of DHAA to total AA we re significantly higher in active and passive smokers than nonexposed nonsm okers (11.2, 10.3, and 7.1%, respectively; p < 0.05). These results indicat e that passive smoking, as well as direct inhalation of cigarette smoke, af fects the redox status of plasma AA. In passive smokers, the altered redox status of plasma AA suggests an oxidative stress.