Vitamin D levels, insulin resistance, and cardiovascular risks in very young obese children

To examine the relationships of 25-hydroxyvitamin D (25-OHD) levels with the measures of insulin resistance and cardiovascular risk, and identify the clinical factors associated with low 25-OHD in young obese children.

Data from 83 children ages 2-6 years seen for obesity care (clinic latitude 42°N) were analyzed. Insulin resistance [homeostasis model assessment of insulin resistance (HOMA-IR)] and cardiovascular risks were examined in relationship to 25-OHD levels using correlation statistics. χ2 and logistic regression models were applied to identify the factors associated with vitamin D deficiency (25-OHD levels <20 ng/mL) and insufficiency (<30 ng/mL).

Children's mean age was mean 4.9 years and they were predominantly Hispanic. Mean body mass index (BMI) Z-score was 3.2 and mean HOMA-IR was 2.8. Mean 25-OHD was 30.9 ng/mL (6% <20 ng/mL and 46% 20-29 ng/mL). There were no significant correlations between 25-OHD and BMI (Spearman's ρ=-0.096, p=0.389), BMI Z-score (Spearman's ρ=0.104, p=0.350), HOMA-IR (Spearman's ρ=-0.144, p=0.269), total cholesterol (Spearman's ρ=-0.028, p=0.833), or triglycerides (Spearman's ρ=-0.026, p=0.846). Vitamin D deficiency was significantly associated with older age, lower milk intake, and testing in winter months. 25-OHD level <30 ng/mL was associated with older age, African-American and Hispanic race/ethnicity, and testing in winter months. All factors retained significance in a multivariate logistic regression model, with African-American (odds ratio=14.4) and Hispanic (odds ratio=7.2) race/ethnicity being the strongest predictors of 25-OHD levels <30 ng/mL.

In these children, 25-OHD was not associated with insulin resistance or cardiovascular risks. Considering age, race/ethnicity, diet, and season may help identify young obese children needing vitamin D management.