Erythrocyte vitamin E and plasma ascorbate concentrations in relation to erythrocyte peroxidation in smokers and nonsmokers: dose response to vitamin E supplementation.

Many human degenerative diseases involve free radical processes that nutritional antioxidants may ameliorate or prevent, but the optimum intake of such nutrients has yet to be established. Requirement will depend in part on the level of exposure to exogenous and endogenous reactive oxygen species. Smokers incur a sustained degree of oxidant stress from both of these sources, increasing their requirements for vitamins E and C. Male smokers (n = 50) from a Scottish population with habitually low vitamin E and vitamin C intakes consistently had lower plasma ascorbate concentrations (P < 0.02) and greater susceptibility to hydrogen peroxide-stimulated erythrocyte peroxidation in vitro (P < 0.001) than did nonsmokers (n = 50) from the same population. Erythrocyte vitamin E concentrations increased in a dose-dependent manner during 20 wk of supplementation with 70, 140, 560, and 1050 mg D-alpha-tocopherol/d. In smokers each dose was associated with a significant decrease in susceptibility of erythrocytes to peroxidation (P < 0.001). However, red cells of nonsmokers receiving the 1050-mg supplement had an increased susceptibility to peroxidation. Moreover, prolonged supplementation with D-alpha-tocopherol in nonsmokers induced a decline in plasma ascorbate concentration (P < 0.02) in association with an increasing erythrocyte vitamin E uptake (P < 0.001), and in nonsmokers receiving 1050 mg, the susceptibility to peroxidation also increased (P < 0.001). Thus, vitamin E may have prooxidant activity in nonsmokers at high and prolonged intakes.