Ethnicity, gender and seasonal variations all play a role in vitamin D deficiency

Aim (1) To explore the adherence of recommendations of vitamin D supplementation to children aged 0-4 years. (2) To compare serum levels of vitamin D in children and adolescents aged 0-17 years originating from different parts of the world. (3) To compare levels between boys and girls and (4) To determine seasonal variation. Methods A review of vitamin D levels in children with parents from different parts of the world was conducted. 2502 children aged 0-17 years were included between 22 January 2004 and 17 May 2021. Results Fifty-nine of 363 children aged 0-4 years received the recommended vitamin D supplementation. Children from all parts of the world had lower levels of serum 25(OH)D than Swedish children. Girls from the Indian subcontinent, Middle East and Africa had the lowest levels of s-25(OH)D. Seasonal variation with higher levels during the summer was seen in children from Sweden, the rest of Europe, Russia and Latin America. Overall prevalence of vitamin D deficiency (<= 25 nmol/L) was 928/2198 (42%) in children not receiving supplementation. Seven children had clinical rickets. Conclusion Adherence of giving children aged 0-4 years the recommended vitamin D supplementation was very low. Vitamin D deficiency is common in immigrant children of all ages in Sweden.