Positive Health Online

Abstract

MCKECHNIE and colleagues, Department of Internal Medicine, Division of Cardiology, University of Michigan Medical Center, Ann Arbor, MI, USA, investigated possible associations of antioxidant supplementation with changes in endothelial function and changes in oxidation of low-density lipoprotein cholesterol (LDLC) in patients with coronary artery disease (CAD).

Background

In population studies, intakes of antioxidants have been found to correlate with CAD. However, formal clinical trials have produced inconsistent findings.

Methodology

This was a double-blind, randomized, placebo-controlled, 12-week trial. 18 patients (mean age 62.4 years) with established CAD received one of three study treatments daily: 1) 400 IU vitamin E, 500 mg vitamin C + 12 mg beta-carotene; 2) 800 IU vitamin E, 1000 mg vitamin C + 24 mg beta-carotene; or 3) placebo. Smokers and patients with diabetes were excluded from the study. Changes (percent and absolute) in brachial artery diameter in response to reactive hyperaemia induced by occlusion release were measured for assessment of endothelial function. Measures of low-density lipoprotein (LDL) oxidation (lag phase), endothelial function, dietary composition, serum antioxidants and lipids were recorded at baseline and 12 weeks.

Results

There were significant differences in the changes in plasma levels of alpha-tocopherol, vitamin C and beta-carotene between the placebo and the antioxidant-supplemented groups at 12 weeks. Although all three groups of patients showed significant improvements in lag phase from baseline, the change was greater in antioxidant-supplemented compared with placebo-treated patients; however, this difference was not statistically significant. Antioxidant-supplemented patients showed a slight but statistically non-significant improvement in brachial reactivity from baseline to 12 weeks, whereas a significant improvement in this measure was observed in the placebo group. Change in lag phase appeared to be unrelated to change in endothelial function. After adjusting for confounding factors, the investigators found that antioxidant supplementation was not a significant predictor of brachial reactivity.

Conclusion

Dietary supplementation with antioxidants caused no significant changes in brachial artery reactivity, although it did significantly increase plasma antioxidant concentrations and improve lag phase. Larger-scale trials are needed to confirm the present findings. Further studies should also evaluate effects of dietary supplementation with individual antioxidants.

References

McKechnie R et al. Antioxidant nutrient supplementation and brachial reactivity in patients with coronary artery disease. The Journal of Laboratory and Clinical Medicine 139 (3): 133-9. Mar 2002.