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 October, the deficiency and severe deficiency were still noticed in 25.9 and 0.1% of children, respectively. The mean serum concentration of 25-OHD was 52% higher in October (55.414.0 nmol/L) than in March (36.4 +/- 13.5 nmol/L), (p<0.01). In children with 25-OHD<50 nmol/L in March, their 25-OHD concentration increased by 64% through March to October (32.5 +/- 8.2 vs. 53.2 +/- 7.9 nmol/L, p<0.01). An association was found between 25-OHD concentration and regular consumption of vitamin D supplements, cod-liver oil and fish. Conclusions The majority of preadolescent Polish boys and girls show vitamin D deficiency after the winter period, although a distinct amelioration over summertime is found in this age group. There is a need to implement effective prevention and intervention strategies in the management of vitamin D deficiency among schoolchildren in Poland, with the supplementation throughout the entire year.