Vitamin C and the risk of acute myocardial infarction

Abstract

Background: Low-fat soluble-antioxidant status is associated with an increased risk of heart disease. Objective: The aim of this study was to examine whether low plasma concentrations of vitamin C confer an independent risk of acute myocardial infarction (AMI). Design: Male patients (n = 180) aged <65 y with a first AMI and without an existing diagnosis of angina (>6 mo) who were admitted within 12 h after onset of symptoms were compared with apparently healthy volunteers (n = 177). Plasma concentrations and dietary intakes of vitamin C were determined during hospitalization and 3 mo later. Results: Compared with the control subjects, the patients had higher total cholesterol and lower HDL-cholesterol concentrations and more of them smoked. The relative risk of AMI for the lowest compared with the highest quintile of plasma vitamin C during hospitalization (14.5 and >60.5 μmol/L, respectively) was 8.37 (95% CI: 3.28, 21.4) after adjustment for classic risk factors. At 3 mo, mean (±SEM) plasma vitamin C concentrations in patients had increased significantly, from 19.6 ± 1.2 to 35.1 ± 1.9 μmol/L (P < 0.001) and no longer conferred a risk of AMI [relative risk: 1.02 (95% CI: 0.51, 2.03)]. Habitual dietary vitamin C intake of patients (before AMI) did not differ significantly from that of control subjects. The increase in plasma vitamin C after recovery from the infarction could not be explained by a similarly large increase in dietary vitamin C. Conclusions: A low plasma concentration of vitamin C was not associated with an increased risk of AMI, irrespective of smoking status. The apparent risk of AMI due to a low plasma vitamin C concentration was distorted by the acute phase response.