Plasma antioxidants, indices of lipid peroxidation and coronary heart disease risk factors in a Scottish population

We have measured coronary heart disease (CHD) risk factors, dietary antioxidant intakes, plasma antioxidant concentrations, activities of blood antioxidant enzymes and plasma indices of lipid peroxidation in current smokers, past-smokers and those who have never smoked (sample size = 242; mean age +/- SE = 54 +/- 1 yr). Compared with non-smokers, both current smokers and past-smokers had increased plasma concentrations of low density lipoproteins (LDL) (P = 0.027) and triglycerides (P < 0.001). Plasma vitamin C concentrations were 40% less in current smokers (P < 0.001), and concentrations in those who had given up smoking were intermediate between smokers and those who had never smoked. As daily vitamin C intakes were similar irrespective of smoking habit and history, current and past smokers may have an increased turnover of the vitamin. There were no differences between the groups in daily intakes or plasma concentrations of vitamin E, vitamin A or carotenoids. Smoking depressed plasma glutathione peroxidase activity (P < 0.001) and increased plasma conjugated diene concentrations (P = 0.047) consistent with the view that smokers are under a sustained oxidative load. The dienes correlated significantly with plasma LDL (P < 0.001) and triglycerides (P < 0.001) but not with high density lipoproteins (HDL). The majority of the population did not consume the recommended daily allowance for vitamins E and C and carotene intakes were also low. An inadequate antioxidant status combined with the sustained free radical load caused by smoking may exacerbate the oxidation of LDL and increase its atherogenic properties, particularly in a population at high CHD risk.