Serum 25-hydroxyvitamin D levels in preschool-age children in northern Sweden are inadequate after summer and diminish further during winter

Abstract

Background and objective: Despite studies indicating that vitamin D intake among Swedish children does not meet the recommendation, little is known of their vitamin D status. The aim of the present study was to examine vitamin D status in preschool-age children in relation to vitamin D intake, season, body mass index, and skin color.

Methods: Preschool-age children (n = 90; mean age 54 ± 7.1 months), all living in northern Sweden (latitude 63° north), half of them with fair skin, half with darker complexion, were recruited from well-baby clinics. The study group was examined first in August-September (late summer) and then the following January-February (winter). Skin type, vitamin D intake, anthropometrics, serum 25-hydroxyvitamin D (S-25[OH] D), and serum parathyroid hormone were assessed.

Results: Mean ± SD S-25(OH) D in summer and winter were 60 ± 15 nmol/L and 55 ± 16 nmol/L, respectively (P < 0.001). Fifteen percent and 10% had S-25(OH) D ≥ 75 nmol/L, and 25% and 40% had S-25(OH) D <50 nmol/L, respectively. The mean vitamin D intake was higher in dark-skinned compared with fair-skinned children. In spite of this, S-25(OH) D in dark-skinned children was lower compared with fair-skinned children during both seasons. The dietary intake of vitamin D was positively associated with S-25(OH) D levels.

Conclusions: Vitamin D status is inadequate in preschool-age children living in northern Sweden, especially in dark-skinned children and during the winter despite vitamin D intakes meeting the recommendations, prompting strategies to improve intake of vitamin D in this population.