While reports of inadequate vitamin D intakes among young children are widespread, data on the prevalence of vitamin D deficiency are inconsistent. We aimed to quantify vitamin D intake and serum 25-hydroxyvitamin D [25(OH)D] concentrations in children aged 2 years in the prospective Cork BASELINE Birth Cohort Study.
Serum 25(OH)D was analysed using UPLC-MS/MS in 741 children living in Cork, Ireland (51A degrees N). Two-day weighed food diaries were collected in 467 children, and 294 provided both a blood sample and a food diary.
Mean (SD) 25(OH)D concentrations were 63.4 (20.4) nmol/L [winter: 54.5 (19.9), summer: 71.2 (17.5)]. The prevalence of vitamin D deficiency (< 30 nmol/L) was 4.6, and 26.7% were < 50 nmol/L [45.2% during winter (November-April) and 10.4% in summer (May-October)]. With a mean (SD) vitamin D intake of 3.5 (3.1) A mu g/day, 96% had intakes below 10 A mu g/day, the current IOM estimated average requirement and the SACN safe intake value for this age group. After adjustment for season, vitamin D intake (A mu g/day) was associated with higher 25(OH)D concentrations [adjusted estimate (95% CI) 2.5 (1.9, 3.1) nmol/L]. Children who did not consume vitamin D-fortified foods or supplements had very low vitamin D intakes (1.2 (0.9) A mu g/day), and during winter, 12 and 77% were < 30 and < 50 nmol/L, respectively, compared with 6 and 44% of fortified food consumers.
There was a high prevalence of low vitamin D status during winter, especially among children who did not consume fortified foods or nutritional supplements. Our data indicate the need for dietary strategies to increase vitamin D intakes in this age group. This report provides further evidence that DRVs for vitamin D should be based on experimental data in specific population groups and indicates the need for dose-response RCTs in young children.