Evidence of a significant vitamin D deficiency among 9–13-year-old Polish children: results of a multicentre study

Purpose To evaluate the extent to which the population of Polish preadolescents is vitamin D deficient and to assess seasonal variations in vitamin D status. Participants and methods A total of 720 healthy children aged 9–13 years (409 girls, 311 boys) residing in 6 representative geographical locations in Poland were studied. A parental-assisted questionnaire provided data on nutritional habits, vitamin D supplements and sun exposure. Serum concentration of 25-hydroxyvitamin was determined twice, after the winter in March and after the summer in October. Results In March, vitamin D deficiency (25–50 nmol/L) was found in 64%, and severe deficiency (< 25 nmol/L) in 20.2% of children. In Octo…