Serum 25-hydroxyvitamin D concentrations in relation to cardiometabolic risk factors and metabolic syndrome in postmenopausal women

Background: Low concentrations of serum 25-hydroxyvitamin D [25(OH)D] may be associated with cardiometabolic disorders; however, little is known about their relation to intermediate metabolic and lipid markers. Objective: We investigated the relation of serum 25(OH)D concentrations to fasting insulin, glucose, dyslipidemia, adiposity, and prevalent metabolic syndrome. Design: We conducted this cross-sectional analysis in 292 postmenopausal women aged 50-79 y in the Women's Health Initiative Calcium-Vitamin D (WHI-CaD) trial. Data were collected from 3 nested case-control studies that measured baseline serum 25(OH)D concentrations. Inverse probability weighting was used to approximate parameter estimates for the WHI-CaD population. Results: In weighted linear regression models adjusted for age, race-ethnicity, month of blood draw, region, case-control status, smoking, alcohol, physical activity, and history of cardiometabolic risk factors, there was an inverse association of serum 25(OH)D with adiposity [body mass index (BMI): beta = 21.12 +/- 0.30, P = 0.0002; waist circumference: beta = 23.57 +/- 0.49, P < 0.0001; waist-hip ratio: beta = 20.01 +/- 0.002, P < 0.0001], triglycerides (beta = -0.10 +/- 0.02, P < 0.0001), and triglyceride: HDL-cholesterol ratio (beta = 20.11 +/- 0.03, P = 0.0003). The multivariable-adjusted odds ratio for metabolic syndrome for the highest (>= 52 nmol/L) compared with the lowest (<35 nmol/L) tertile of serum 25(OH)D concentrations was 0.28 (95% CI: 0.14, 0.56). Significant associations remained after adjustment for BMI. We observed no significant associations with LDL cholesterol, HDL cholesterol, insulin, glucose, homeostatic model assessment of insulin resistance (HOMA-IR), or homeostatic model assessment of beta cell function (HOMA-beta). Conclusion: Higher serum 25(OH)D concentrations may be inversely associated with adiposity, triglycerides, triglyceride: HDL-cholesterol ratio, and metabolic syndrome but are not associated with LDL and HDL cholesterol, insulin, glucose, HOMA-IR, or HOMA-beta in post-menopausal women. This trial was registered at clinicaltrials.gov as NCT00000611. Am J Clin Nutr 2011;94:209-17.