Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) study: a randomized trial of the effect of vitamins E and C on 3-year progression of carotid atherosclerosis.

Objectives: To study the efficacy of vitamin E and C supplementation on the progression of carotid atherosclerosis, hypothesizing an enhanced preventive effect in men and in smokers and synergism between vitamins.

Design And Subjects: Double-masked two-by-two factorial trial, randomization in four strata (by gender and smoking status) to receive twice daily either 91 mg (136 IU) of d-alpha-tocopherol, 250 mg of slow-release vitamin C, a combination of these or placebo for three years. A randomized sample of 520 smoking and nonsmoking men and postmenopausal women aged 45-69 years with serum cholesterol >/= 5.0 mmol L-1 were studied.

Setting: The population of the city of Kuopio in Eastern Finland.

Intervention: Twice daily either a special formulation of 91 mg of d-alpha-tocopherol, 250 mg of slow-release vitamin C, a combination of these (CellaVie(R)) or placebo for three years.

Measurements: Atherosclerotic progression, defined as the linear regression slope of ultrasonographically assessed common carotid artery mean intima-media thickness (IMT), was calculated over semi-annual assessments.

Results: The average increase of the mean IMT was 0.020 mm year-1 amongst men randomized to placebo and 0.018 mm year-1 in vitamin E, 0.017 mm year-1 in vitamin C and 0.011 mm year-1 in the vitamin combination group (P = 0.008 for E + C vs. placebo). The respective means in women were 0.016, 0.015, 0.017 and 0.016 mm year-1. The proportion of men with progression was reduced by 74% (95% CI 36-89%, P = 0.003) by supplementation with the formulation containing both vitamins, as compared with placebo.

Conclusions: Our study shows that a combined supplementation with reasonable doses of both vitamin E and slow-release vitamin C can retard the progression of common carotid atherosclerosis in men. This may imply benefits with regard to other atherosclerosis-based events.