Higher vitamin D intake is needed to achieve serum 25(OH)D levels greater than 50 nmol/l in Québec youth at high risk of obesity.

BACKGROUND/
OBJECTIVES: Vitamin D levels are often observed to be low in Canadian youth, despite the mandatory fortification of fluid milk. We identified modifiable correlates of plasma vitamin D concentrations to inform public health efforts to remediate low-vitamin D status. SUBJECTS/
METHODS: We recruited 159 children aged 8-11 years, who were at at high risk of obesity, non-systematically during different seasons. Vitamin D status was assessed by measuring plasma 25-hydroxyvitamin D (25(OH)D) using a radioimmunoassay. Dietary intake, including vitamin supplements, was measured using three dietitian-administered 24 h diet recalls. Fat mass was measured by dual energy X-ray absorptiometry. Accelerometers were worn for 7 days to estimate physical activity. Independent correlates of plasma 25(OH)D concentrations were identified using multiple regression in an analysis controlling for season of measurement.
RESULTS: Approximately, 7% of youth had hypovitaminosis D (25(OH)D ≤37.5 nmol/l) during winter and spring when vitamin D levels are at their nadir. Only 55% of participants had vitamin D levels, which the Institute of Medicine considers optimal (25(OH)D >50 nmol/l). The mean dietary vitamin D intake, 6.6 mcg, was well below current recommendations set at 15 mcg. A serving increase in milk consumption and a s.d. increase in physical activity were associated with only a 2.9 and 2.1 nmol/l increase in plasma 25(OH)D, respectively. There was no association between 25(OH)D and adiposity.
CONCLUSIONS: Our results indicate the challenges of obtaining adequate vitamin D intake from the current food supply to support a level of 25(OD)D >50 nmol/l.