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): β = -1.12 ± 0.30, P = 0.0002; waist circumference: β = -3.57 ± 0.49, P < 0.0001; waist-hip ratio: β = -0.01 ± 0.002, P < 0.0001], triglycerides (β = -0.10 ± 0.02, P < 0.0001), and triglyceride:HDL-cholesterol ratio (β = -0.11 ± 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 β cell function (HOMA-β).
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-β in postmenopausal women. This trial was registered at clinicaltrials.gov as NCT00000611.