Longitudinal association of measures of adiposity with serum antioxidant concentrations in postmenopausal women

BACKGROUND/OBJECTIVES: The relationship between obesity and circulating levels of antioxidants is poorly understood. Most studies that have examined the association of adiposity with blood or tissue concentrations of antioxidant micronutrients have been cross-sectional, and few have compared the associations for indices of overall obesity and central obesity. Our aim was to prospectively examine the longitudinal association of body mass index (BMI), waist circumference (WC), waist circumference-height ratio (WCHtR) and waist-hip ratio (WHR) with major serum antioxidants in a population of postmenopausal women. SUBJECTS/METHODS: We used a subsample of participants in the Women's Health Initiative aged 50-79 years at entry with available fasting blood samples and anthropometric measurements obtained at multiple time points over 12.8 years of follow-up (N = 2672). Blood samples were used to measure a-carotene, beta-carotene, beta-cryptoxanthin, lutein+zeaxanthin, a-tocopherol, gamma-tocopherol and retinol at baseline, and at years 1, 3 and 6. We used mixed-effects linear regression analyses to examine associations between anthropometric measures and serum antioxidants at baseline and over time, controlling for covariates. RESULTS: In longitudinal analyses, carotenoids, and particularly beta-carotene, were strongly and inversely associated with BMI, WC and WCHtR and less so with WHR. a-Tocopherol showed a strong positive association with WHR but not with other anthropometric measures, whereas gamma-tocopherol was positively and strongly associated with BMI, WC, WCHtR and less so with WHR. Retinol was positively associated with WHR. The inverse association of several carotenoids with anthropometric measures was stronger in never and former smokers compared with current smokers and in women without the metabolic syndrome. The inverse association of carotenoids with obesity measures may reflect reduced micronutrient concentrations owing to inflammation associated with obesity. CONCLUSIONS: In the present study, the strongest observed associations between anthropometric variables and micronutrients were an inverse association of WC with serum beta-carotene and a positive association of WC with gamma-tocopherol.