Seasonal Vitamin D Status of Healthy Schoolchildren and Predictors of Low Vitamin D Status

• Published in: Journal of pediatric gastroenterology and nutrition Vol. 58; no. 5; pp. 654 - 660
• Main Authors: Karagüzel, Gülay, Dilber, Beril, Çan, Gamze, Ökten, Ayşenur, Değer, Orhan, Holick, Michael F.
• Format: Journal Article
• Language: English
• Published: United States by European Society for Pediatric Gastroenterology, Hepatology, and Nutrition and North American Society for Pediatric Gastroenterology 01.05.2014
• Subjects: 25‐hydroxyvitamin D; Adolescent; Child; Cross-Sectional Studies; Dietary Supplements; Exercise; Female; Humans; Male; parathyroid hormone; Parathyroid Hormone - blood; schoolchildren; season; Seasons; Sex Factors; Sunlight; Surveys and Questionnaires; vitamin D; Vitamin D - administration & dosage; Vitamin D - analogs & derivatives; Vitamin D - blood; Vitamin D Deficiency - blood; Vitamin D Deficiency - epidemiology; Vitamin D Deficiency - prevention & control
• ISSN: 0277-2116; 1536-4801
• DOI: 10.1097/MPG.0000000000000274

ABSTRACT Objectives: The aim of the study was to assess seasonal prevalence of vitamin D deficiency according to sex and to determine the relations between serum levels of 25‐hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH) and sociodemographic characteristics in otherwise healthy schoolchildren during spring and autumn. Methods: In a cross‐sectional study, 746 healthy students aged between 11 and 18 years were recruited during spring (n = 375) and autumn (n = 371). Sociodemographic data were collected by a questionnaire. Serum 25(OH)D, PTH, calcium, phosphate, and alkaline phosphatase were measured. Serum 25(OH)D levels were categorized as <50 nmol/L (vitamin D deficiency) and <25 nmol/L (severe deficiency). Results: Mean ± standard deviation 25(OH)D levels were 22.3 ± 10.5 nmol/L in girls and 28.5 ± 17.0 nmol/L in boys during spring (P < 0.001) and 36.5 ± 20.3 nmol/L in girls and 45.0 ± 18.5 nmol/L in boys during autumn (P < 0.001). The prevalence of vitamin D deficiency was 93% during spring and 71% during autumn. There was a negative correlation between 25(OH)D and PTH levels (P < 0.01). We determined a cutoff point of serum 25(OH)D in which the mean serum PTH concentration began to increase as 35.8 nmol/L (P < 0.0001). The age, sex, and calcium level were found to be independent predictors for vitamin D deficiency. Conclusions: Vitamin D deficiency is prevalent among healthy schoolchildren. It is noteworthy that 25(OH)D levels were significantly lower in girls and during autumn. We recommend vitamin D supplementation for children in addition to more time spent for outdoor activities for sensible sunlight exposure.