Effect of Antioxidant Vitamins on the Transient Impairment of Endothelium-dependent Brachial Artery Vasoactivity Following a Single High-fat Meal

Context: Much has been written about the potential role of antioxidants in the prevention of atherosclerosis.

Objective: To assess the short-term effect of a single high-fat meal with and without pretreatment with antioxidant vitamins on endothelial function in healthy, normocholesterolemic subjects.

Design: Observer-blinded randomized trial.

Setting: University hospital.

Participants: Twenty healthy, normocholesterolemic (total and low-density lipoprotein cholesterol <5.2 mmol/L and <3.4 mmol/L [<200 mg/dL and <130 mg/ dL], respectively), male (7) and female (13) hospital employee volunteers, aged 24 to 54 years.

Intervention: Three randomly administered breakfasts: (1) a high-fat meal (3766 J [900 calories], 50 g of fat); (2) a low-fat meal (3766 J [900 calories], 0 g of fat); and (3) a high-fat meal and pretreatment with oral administration of vitamins C (1 g) and E (800 IU) (high-fat meal with vitamins). A subgroup of 10 subjects also ate the low-fat meal with the same vitamin pretreatment (low-fat meal with vitamins).

Main Outcome Measure: High-resolution ultrasound assessed flow-mediated (endothelium-dependent) brachial artery vasodilation measured as percent diameter change before and hourly for 6 hours following each meal.

Results: Flow-mediated vasodilation fell from a mean+/-SD of 20%+/-8% before to 12%+/-6%, 10%+/-6%, and 8%+/-9% at 2, 3, and 4 hours, respectively, after the high-fat meal (P<.001). No significant changes in flow-mediated vasodilation occurred after the low-fat meal, high-fat meal with vitamins, or low-fat meal with vitamins. The change in flow-mediated vasodilation after the low-fat and high-fat meals correlated inversely with the 2-hour postprandial change in triglyceride levels (r=-0.54; P<.001).

Conclusion: A single high-fat meal transiently reduces endothelial function for up to 4 hours in healthy, normocholesterolemic subjects, probably through the accumulation of triglyceride-rich lipoproteins. This decrease is blocked by pretreatment with antioxidant vitamins C and E, suggesting an oxidative mechanism.