Body Mass Index is a Strong Predictor of Low Serum 25(OH)D Levels in Multiethnic Obese Children in Western Massachusetts

Abstract

The objective of the study is to examine the association between low serum 25(OH)D levels (VDL) and BMI category in children, adjusting for sex, ethnicity, age, CVD risk markers, season and nutrient intakes. 99 obese (BMI> 95%) children aged 5–16 years participated in this cross sectional study conducted in a Pediatric Weight Management Clinic in Western Massachusetts. Nutrient intakes (Block Kids 2004 FFQ) and serum 25(OH)D were measured. Sunlight exposure, BMI, waist circumference (WC), BP, ethnicity, 25(OH)D, calcium, PTH, HbA1C, AST/ALT, fasting insulin, glucose, lipids and hsCRP data were obtained. Multivariable logistic regression was used to examine the relationship between VDL and BMI category, adjusting for potential confounders. Of 91 children completing the FFQ, mean 25(OH)D was 21.2 (±7.7) ng/mL and the mean BMI z‐score was 2.4 (±0.4). Using the Institute of Medicine (IOM) criteria, 25(OH)D was categorized into <15ng/mL (22.0%) and normal (≥15 ng/mL; 78%)., and BMIz, into >2.5 37.4%) and ≤ 2.5 (62.6%. Mean age 10.9±2.6 (SD) yrs, 22.0% African American, 26.4% Caucasian and 51.7% Hispanic, 52.8% female. Among those with BMI z‐scores less than 2.5, 15.8% had low 25(OH)D levels vs. 32.4% among those with BMI z‐scores at 2.5 or greater. That is, children with BMI z‐scores > 2.5 have 2.55 greater odds of having a low 25(OH)D level compared to those with BMI z‐scores <2.5 (OR=2.55, 95%CI: 0.93, 11.16; p=0.07). In logistic regression analysis, adjusting for gender, ethnicity, season, and age, children with BMI z‐scores >2.5 had a significant 5.14 greater odds of low 25(OH)D compared to children with BMI z‐scores ≤2.5 (95%CI: 1.30, 20.36; p = 0.02). Additional adjustment for energy‐adjusted nutrient values, waist circumference, and selected cardiovascular risk factors did not change this relationship. Obese children are at risk for vitamin D deficiency. This risk increases in children with severe obesity (BMIz > 2.5 SD) and is not significantly changed by season, ethnicity, nutrient intakes or sunlight exposure. More research is needed to further elucidate the mechanisms that influence vitamin D levels in this vulnerable population.Support or Funding InformationThis work was funded by UMASS‐Baystate Medical Center Collaborative Biomedical Research.