Background: Smoking is a very deadly act with a very high mortality rate associated with smoking-related illnesses. Recently, there has been major concern that passive smokers face the same health risk as active smokers. Cotinine is a major nicotine metabolite that may be used as a marker for both active smoking and as an index to environmental tobacco smoke exposure. Animal studies show that nicotine inhibits anti-oxidant enzymes and is associated with low levels of vitamins.

Research objectives: To estimate the levels of cotinine, Vitamin A, E, C and catalase and establish a relationship between them in the two groups of smokers.

Methods: Serum levels of cotinine, Vitamin A, E and C and catalase were estimated in 30 cigarette smokers, 30 passive smokers and 30 non-smokers recruited from Calabar metropolis.

Results and conclusion: Serum cotinine levels were significantly (p>0.05) higher in active smokers who had a mean cotinine value of 67.67±11.50ng/ml than in passive smokers that had a mean cotinine level of 2.44±0.36ng/ml and controls whose mean cotinine levels were 0.96±0.24ng/ml. Serum vitamins A and E were significantly (p<0.05) lower in active (with mean values of 53.99±1.99µg/dl and 31.67±2.59mg/ml respectively) and passive smokers (with mean values of 51.14±0.80µg/dl and 37.30±1.68mg/ml respectively) when compared to that of controls (67.49±1.50µg/dl and 55.81±1.67mg/ml respectively). However there was no significant difference in the serum Vitamin C levels among the three groups. The mean catalase level of active smokers was 48.55±11.80µmol/ml/min and was significantly (p<0.05) lower than that of the controls (53.32±7.59µmol/ml/min). There was a significant positive correlation between Vitamins A and E in both active smokers (r=0.443; p<0.05) and passive smokers (r=0.513; p<0.05). Passive and active smoking depletes vitamins A and E and catalase, this may be a contributing factor to the diseases linked to cigarette smoking.