Serum 25-Hydroxyvitamin D associated with indicators of body fat and insulin resistance in prepubertal chilean children

Abstract

BACKGROUND: Consistent data on the relation between vitamin D, body fat and insulin resistance (IR) in children are lacking. OBJECTIVES: (1) To evaluate the association between serum 25-Hydroxyvitamin D [25(OH)D] and key indicators of: adiposity (total and central), IR, and (2) to estimate serum 25(OH)D cut-offs that best reflect IR and total and central adiposity in children. SUBJECTS/METHODS: Prepubertal children (n = 435, ~ 53% girls; ~ age 7 years) from the Growth and Obesity Chilean Cohort Study were evaluated for potential associations between serum 25(OH)D and indicators of: (1) total adiposity (body mass index by age (BAZ), body fat (including three-component model)), central adiposity (waist circumference and trunk fatness); (2) IR (homeostasis model assessment of IR) and insulin sensitive (quantitative insulin sensitivity check index) using standardized multiple regression models with standardized coefficients and receiver operating characteristic curves. RESULTS: Overall, mean serum 25(OH)D was 32.1 ± 9.2 ng ml− 1, while 19.4% of children were obese (BAZ ⩾2 s.d.). Serum 25(OH)D was inversely associated with indicators of total and central adiposity and with IR indicators. Effect sizes were moderate in girls (~0.3 for adiposity and IR indicators), while, weaker values were found in boys. Serum 25(OH)D estimated cut-offs that best predicted total, central adiposity and IR were ~ 30 ng ml− 1. Children with suboptimal serum 25(OH)D (o30 ng ml− 1) had a higher risk (two to three times) of being obese (high BAZ, body fat percent and/or central adiposity); and three to four times greater risk for IR. CONCLUSIONS: Serum 25(OH)D was inversely associated with adiposity (total and central) and IR indicators in prepubertal Chilean children. The conventional cut-off of vitamin D sufficiency (⩾30 ng ml− 1) was adequate to assess obesity and IR risk in this age group.