Suboptimal Vitamin D Status Despite Supplementation in Children with Cystic Fibrosis and Its Association with Growth Indices

Background and Objectives: Vitamin D deficiency is prevalent in patients with cystic fibrosis. However, possible effects of vitamin D deficiency on growth of children with cystic fibrosis is still unclear. The aim of this study was to assess vitamin D status and its associations with growth indices in cystic fibrosis children. Materials and Methods: This cross-sectional descriptive study was carried out on registered cystic fibrosis patients residing in West Azerbaijan Province, Iran. Demographic, anthropometric and dietary assessments were carried out as well. The growth indicators, including weight‐for‐age, length‐for‐age, weight‐for‐length and body mass index‐for‐age Z-scores and percentiles, were assessed based on recommendations by World Health Organization and Centers for Disease Control and Prevention. Vitamin D status was assessed using serum 25-hydroxycalciferol [25(OH)D3] assay and concentrations of less than 20 and 20–30 ng/ml were considered deficiency and insufficiency, respectively. Results: A total of 38 cystic fibrosis patients aged 91.7 m ±62.6 were enrolled in the study. Numbers of participants with no supplementation, insufficient ( 400 IU [ 1 y] and 800 IU [ 1 y]) and sufficient supplementation were 12 (31.6%), 12 (31.6%) and 14 (36.8%), respectively. However, frequency of vitamin D insufficiency and deficiency was 30 (78.9%). Positive correlations between serum concentration of (25(OH)D3) and weight‐for‐age and body mass index for age Z-scores were reported. Based on body mass index for age percentile, healthy weight participants had higher serum concentrations of (25(OH)D3), compared to underweight patients (28.8 ±11 against 20.9 ±3.4; p 0.05). Conclusions: This study revealed that supplementation could improve serum concentrations of (25(OH)D3); however, rate of vitamin D insufficiency was high (64%)even in sufficiently supplemented participants. Appropriate supplementation and maintaining desired levels of 25(OH)D3 may have beneficial effects on cystic fibrosis patients’ growth.