Are national vitamin D guidelines sufficient to maintain adequate blood levels in children?

BACKGROUND Vitamin D insufficiency (defined as 25-hydroxyvitamin D [25(OH)D] concentrations <40 nmol/L) may be associated with subclinical adverse effects on bone mineralization. The current vitamin D status of children and adolescents in Canada has not been described. The purpose of this study was to describe the association between 25(OH)D serum concentration and dietary vitamin D intake, and other potential determinants of vitamin D status, among a sample of children and adolescents aged 2-16 years presenting to a pediatric emergency department in Edmonton, Alberta (latitude 52 degrees N) at the end of winter. METHODS In early April 2003, 90 patients between the ages of 2 and 16 years who presented to the pediatric emergency department in Edmonton volunteered to participate. All participants and/or parents or guardians completed questionnaires regarding potential risk factors for vitamin D insufficiency, detailed dietary assessments, and anthropometric measurements. Serum 25(OH)D concentrations were measured in 68 of 90 participants. RESULTS The mean serum 25(OH)D concentration was 47.2 nmol/L (95% CI 43.8-50.8 nmol/L). 34% of participants had vitamin D insufficiency (<40 nmol/L) and 6% were deficient (<25 nmol/L). Boys and girls aged 9-16 years had a prevalence of insufficiency of 69% and 35% respectively, while boys and girls 2-8 years old had a prevalence of insufficiency of 22% and 8% respectively. Dietary vitamin D intake per kilogram body weight was the most important independent determinant of 25(OH)D concentration (r = 0.446, p<0.001). Vitamin D intake, age and male sex best predicted insufficiency. No subject was insufficient if they had an intake >0.45 mcg/kg/day. INTERPRETATION Vitamin D insufficiency may be common among children and adolescents at the beginning of spring. The risk may be highest among older children because vitamin D intake does not adequately rise in proportion with increases in body mass. Further studies are needed to assess whether Canadian dietary vitamin D recommendations should be changed.