Vitamin D status and its predictors among pre-school children in Adelaide

Aim To assess vitamin D status and its predictors in a representative population sample of pre-school children in Adelaide (latitude of 35°S). Methods Cross-sectional survey of children aged between 1 and 5 years from areas of low, medium and high socio-economic status as identified from the 2001 Census data, Australian Bureau of Statistics. Children were recruited between September 2005 and July 2007 using a door knocking protocol based on a stratified sampling method to obtain a representative sample of this age group. Serum 25-hydroxyvitamin D (25(OH)D) was determined using a radio-immunoassay kit. Vitamin D deficiency was defined as serum 25(OH)D) <30 nmol/L and insufficiency defined as serum 25(OH)D ≥30 and <50 nmol/L according to the Institute of Medicine. Results Fifty-two per cent of eligible children took part in the study. Mean (standard deviation) serum 25(OH)D was 73 (26) nmol/L (n = 221). The prevalence of vitamin D deficiency and insufficiency was 4% and 16%, respectively, with the prevalence being higher in winter (8% and 22%, respectively). Season of the year of blood collection and mother being born in Australia were significant predictors of serum 25(OH)D concentration, but age, sex, socio-economic status, BMI category or dietary supplement use were not related to vitamin D status. Conclusions Vitamin D status of this representative sample of pre-school children in Australia is adequate, and the prevalence of vitamin D deficiency is low based on the Institute of Medicine criteria.