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Evidence suggests that the antioxidant micronutrients, vitamin E, vitamin C, and beta carotene, may be protective against coronary artery disease, perhaps through inhibition of the oxidation of low-density lipoprotein (LDL) (1-5). Previous studies have described the relationship between anti-oxidant micronutrient intake and plasma antioxidant concentrations in healthy volunteers (3,4,6). Studies of this relationship in patients with coronary artery disease, however, are limited. The purpose of this study was to examine the relationship between dietary intake and plasma concentrations of antioxidant micronutrients in these patients. We asked the question: What are the determinants of plasma antioxidant micronutrient concentrations in a representative group of patients with coronary artery disease?
Forty-five patients with established coronary artery disease who did not smoke and did not have diabetes were recruited from The University of Michigan Medical Center for a larger clinical trial examining the effects of antioxidants on oxidized LDL. Forty-two of these subjects were part of the final analysis. All subjects had normal hepatic and renal function, showed no evidence of malabsorption or pancreatic or biliary disease, had no acute medical condition for 3 months before study entry, and were not currently receiving resin therapy or taking vitamin supplements that provided greater than 100% of the US Recommended Dietary Allowance levels within the previous 6 months (7). The study was approved by the Institutional Review Board of The University of Michigan School of Medicine.
Height and weight were measured, and body mass index (BMI) was computed as weight (kg)/height ([m.sup.2]). Body composition was estimated from three sex-specific skinfold plus fatfold measurements (8-10). Cholesterol and triglyceride concentrations were determined enzymatically [TABULAR DATA FOR TABLE 1 OMITTED] with commercially available reagents (Sigma Diagnostics, St Louis, Mo) (11,12). LDL cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) were isolated by precipitation (13,14). Plasma carotenoids were separated and quantified based on a high-performance liquid chromatography method (15-17). Accuracy was assessed by periodic analysis of National Institute of Standards and Technology Standard Reference Material 986, Fat-Soluble Vitamins (Gaithersburg, Md, US Department of Commerce), …