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Vitamin C and the risk of acute myocardial infarction
R A Riemersma1, K F Carruthers, R A Elton
1British Heart Foundation Cardiovascular Research Unit, the Department of Cardiology and Medicine, the Royal Infirmary of Edinburgh, Edinburgh, United Kingdom. rudolph.riemersma@ed.ac.uk
Insights
Low vitamin C levels initially appeared to increase heart attack risk, but this was due to the acute phase response, not habitual intake. Subsequent measurements showed no link between vitamin C and acute myocardial infarction risk.
Area of Science:
- Cardiovascular Health
- Nutritional Biochemistry
- Epidemiology
Background:
- Low antioxidant status, including vitamin C, is linked to increased heart disease risk.
- Investigating the independent role of plasma vitamin C in acute myocardial infarction (AMI) is crucial for understanding cardiovascular disease etiology.
Purpose of the Study:
- To determine if low plasma vitamin C concentrations independently predict the risk of acute myocardial infarction (AMI).
- To differentiate the acute effects of AMI on vitamin C levels from habitual intake and long-term risk.
Main Methods:
- A case-control study comparing male patients (n=180) with first AMI to healthy volunteers (n=177).
- Plasma vitamin C concentrations and dietary intakes were assessed during hospitalization and three months later.
- Statistical adjustments were made for classic cardiovascular risk factors including cholesterol, HDL-cholesterol, and smoking status.
Main Results:
- Patients with AMI had higher total cholesterol, lower HDL-cholesterol, and higher smoking rates than controls.
- The lowest quintile of plasma vitamin C during hospitalization showed a significantly elevated relative risk (8.37) for AMI, adjusted for risk factors.
- Plasma vitamin C levels increased significantly three months post-AMI, and the elevated risk of AMI was no longer observed (relative risk: 1.02).
- Habitual dietary vitamin C intake did not differ between patients and controls, and the post-AMI increase in plasma vitamin C was not explained by dietary changes.
Conclusions:
- The apparent association between low plasma vitamin C and AMI risk during hospitalization is likely an artifact of the acute phase response.
- Habitual vitamin C intake, as reflected by dietary patterns, does not appear to be an independent risk factor for AMI.
- Plasma vitamin C levels fluctuate during acute illness, necessitating careful interpretation in relation to disease risk.
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 micromol/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 micromol/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.