LETTER TO THE EDITOR
Reply
Brendan M. McQuillan, MBBS, PhD, FRACP*,
Joseph Hung, MBBS, FRACP, FACC*,
John P. Beilby, PhD, FAACB*,
Mark Nidorf, MD, FRACP, FACC* and
Peter L. Thompson, MD, FRACP, FACC*
* Sir Charles Gairdner Hospital, Department of Cardiovascular Medicine, Hospital Avenue, Nedlands, Western Australia, 6009
brendan.mcquillan{at}health.wa.gov.au
We were very interested in the comments by Drs. Alves-Rodrigues and Thomas regarding the variable results of studies examining the relationship between antioxidant vitamins and atherosclerosis. As they point out, it would be inappropriate to dismiss all antioxidant vitamins with regards to their potential anti-atherogenic properties based on data that demonstrates only weak or no effects for a limited range of vitamins studied. Our study assessed the relationship of dietary intake or plasma levels of a number of antioxidant vitamins with subclinical carotid atherosclerosis in a large (N = 1,111 subjects) randomly selected community population (1). We selected vitamins that are relatively plentiful in Western diets and have been suggested as important antioxidant compounds in studies of lipid oxidation and animal models of atherosclerosis. We observed a weak inverse association between dietary intake of vitamin E and common carotid artery intimal-medial thickness (IMT) in men, with a nonsignificant trend in women. An inverse association was also found between carotid IMT and plasma lycopene in women but not in men. We did not assess dietary intake or plasma levels of lutein in our study, although this could be undertaken.
A number of epidemiologic studies have now demonstrated an association between dietary intake or plasma levels of antioxidant vitamins and the risk of atherosclerotic vascular disease. However, large-scale randomized trials to test further for a causal relationship between antioxidant intake and ischemic heart disease have provided conflicting results (2). Although there is plausible biological evidence to suggest antioxidants may prevent the early stages of atherogenesis, it is unknown as to whether they alter the later processes that produce clinical events. To determine the role of antioxidant vitamins in atherosclerosis, it may be more appropriate to examine the relationship between dietary intake or plasma levels of these vitamins and measures of early atherosclerosis rather than clinical cardiovascular events (3).
Although we remain very interested in investigating antioxidant defenses against lipid peroxidation and novel risk factors for atherosclerosis, we would support the concept that this essential ongoing research should not distract us from efforts to implement more proven preventive strategies (4).
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References
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1. McQuillan BM, Hung J, Beilby JP, et al. Antioxidant vitamins and the risk of carotid atherosclerosis. The Perth Carotid Ultrasound Disease Assessment Study (CUDAS). J Am Coll Cardiol. 2001;38:1788–1794[Abstract/Free Full Text]
2. Diaz MN, Frei B, Vita JA, et al. Antioxidants and atherosclerotic heart disease. N Engl J Med. 1997;337:408–416[Free Full Text]
3. Steinberg D. Clinical trials of antioxidants in atherosclerosis: are we doing the right thing? Lancet. 1995;346:36–38[CrossRef][Medline]
4. Lonn E. Do antioxidant vitamins protect against atherosclerosis? The proof is still lacking. J Am Coll Cardiol. 2001;38:1795–1798[Free Full Text]
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