Vitamin D Intake and Status in 6-Year-Old Icelandic Children Followed up from Infancy

Abstract

High serum 25-hydroxyvitamin D (25(OH)D) levels have been observed in infants in Nordic countries, likely due to vitamin D supplement use. Internationally, little is known about tracking vitamin D status from infancy to childhood. Following up 1-year-old infants in our national longitudinal cohort, our aims were to study vitamin D intake and status in healthy 6-year-old Icelandic children (n = 139) and to track vitamin D status from one year of age. At six years, the mean 25(OH)D level was 56.5 nmol/L (SD 17.9) and 64% of children were vitamin D sufficient (25(OH)D ≥ 50 nmol/L). A logistic regression model adjusted for gender and breastfeeding showed that higher total vitamin D intake (Odds ratio (OR) = 1.27, 95% confidence interval (CI) = 1.08–1.49), blood samples collected in summer (OR = 8.88, 95% CI = 1.83–43.23) or autumn (OR = 5.64, 95% CI = 1.16–27.32) compared to winter/spring, and 25(OH)D at age one (OR = 1.02, 95% CI = 1.002–1.04) were independently associated with vitamin D sufficiency at age six. The correlation between 25(OH)D at age one and six was 0.34 (p = 0.003). Our findings suggest that vitamin D status in infancy, current vitamin D intake and season are predictors of vitamin D status in early school age children. Our finding of vitamin D status tracking from infancy to childhood provides motivation for further studies on tracking and its clinical significance.

Sun behaviour and physical activity associated with autumn vitamin D status in 4–8-year-old Danish children

“…In line with this, others have previously reported that ethnicity is a significant determinant of s-25(OH)D in children (7,15,20,42) . In addition, we cannot rule out the effect of a potential tracking of vitamin D status from infancy as has been reported previously among 6-year-old Icelandic children (41) . Lastly, genetic factors have also been suggested to regulate vitamin D status (43) and we cannot know if this modified the response to sun exposure, for instance.…”

Serum 25-hydroxyvitamin D levels showed strong seasonality but lacked association with vitamin D intake in 3-year-old Japanese children

“…This may have been due to the crudity of our measurement of sunlight exposure, as we measured only outdoor playtime but did not consider the area of skin exposed, sunscreen use or time of day when the exposure occurred, since very little if any vitamin D is produced before 10.00 hours and after 15.00 hours (13) . Several recent studies showed that vitamin D levels could also vary according to social and environmental factors such as skin colour and socio-economic status (45,47,(52)(53)(54) . In our study, we found the risk of vitamin D insufficiency to vary according to parental characteristics (children with the highest risk, that is, children whose mothers reported their own education status but omitted the father's, were likely to be single mothers).…”

Do all infants need vitamin D supplementation?

“…In the present study, no correlation was observed between age of infants and their respective serum concentrations of 25(OH)D. Carpenter and cols [ 8 ] and Alonso and cols [ 35 ] found an inverse correlation between age and 25(OH)D serum concentrations in American and Spanish infants, respectively. In some studies [ 8 , 58 , 62 , 63 ] conducted with infants and children, researchers found that 25(OH)D serum concentrations decreased with age, with a higher proportion of deficient values found in children over two years of age.…”