Vitamin D Status, Adiposity, and Insulin Resistance among U.S. Non-Hispanic Black Women: a Complex-Survey Analysis of NHANES 2011–2018

Non-Hispanic Black women in the United States face disproportionately high rates of obesity, insulin resistance, and type 2 diabetes, along with some of the lowest vitamin D levels of any major racial or ethnic group. Using National Health and Nutrition Examination Survey (NHANES) 2011–2018 data, we examined whether vitamin D status was independently associated with insulin resistance, glycemic markers, and lipid outcomes after accounting for adiposity among non-Hispanic Black women aged 18 years and older. Primary models adjusted for body mass index (BMI) and relevant cardiometabolic covariates, with sensitivity analyses replacing BMI with waist-to-height ratio (WHtR) to assess robustness to alternative measures of adiposity. Glycemic and lipid outcomes were modeled as continuous variables, with fasting subsample weights applied as appropriate. Vitamin D deficiency was common, with only 17.3% (95% CI 15.6–19.1) of participants meeting sufficiency criteria. After adjustment for BMI or WHtR and cardiometabolic covariates, vitamin D status was not independently associated with insulin resistance (HOMA-IR) or hemoglobin A1c. In contrast, adiposity measures remained strongly associated with insulin resistance across models. Higher vitamin D status was consistently associated with a more favorable lipid profile, including lower triglyceride and higher HDL cholesterol, and these associations were robust to adiposity measures. These findings indicate that adiposity is the dominant correlate of insulin resistance among non-Hispanic Black women, whereas vitamin D status is not independently associated with insulin resistance. The observed associations with lipid parameters suggest a domain-specific relationship between vitamin D status and cardiometabolic risk distinct from glycemic regulation.