Vitamin D concentrations among healthy children in Calgary, Alberta.

Objective: To examine the relationship between serum vitamin D concentrations, dietary intake and body mass index among healthy children living in Calgary, Alberta.

Methods: The present cross-sectional study included healthy children two to 13 years of age who presented to the Alberta Children's Hospital for elective surgery during a 12-month period. Data including the child's weight, height, age, sex, ethnicity, dietary intake, use of vitamin supplements, physical activity and time spent outdoors were collected. Serum concentrations of 25-hydroxyvitamin D (25[OH]D) were measured using commercial immunoradiometric assay kits.

Results: Serum 25(OH)D concentrations were available for 1442 of 1862 participants, of whom 862 (59.8%) were boys. The mean (± SD) serum 25(OH)D concentration was 86.1±35.1 nmol/L (range 10 nmol/L to 323 nmol/L). Five hundred thirty-nine (37.4%) participants had insufficient vitamin D status (25[OH]D between 25 nmol/L and lower than 75 nmol/L), and vitamin D deficiency (25[OH]D 25 nmol/L or lower) was present in 29 subjects (2.0%). Children in the older age group (nine to 13 years) were more likely to have suboptimal vitamin D (P<0.001). Other risk factors significantly associated with suboptimal vitamin D status included overweight or obesity, nonwhite ethnicity, winter months, dietary vitamin D intake of less than 200 IU/day and less time spent outdoors.

Conclusion: A high rate of suboptimal vitamin D concentrations was observed among the participants. Beyond promoting a vitamin D-enriched diet, physicians should also consider the body mass index and other risk factors to determine the optimal vitamin D intake for children living in the area studied.