Vitamin D status of 3-year-old children in Denmark: determinants and associations with bone mineralisation and blood lipids

Purpose: Low vitamin D status is a global problem and has been associated with reduced skeletal and cardiometabolic health. However, evidence in young children is lacking. We, therefore, aimed to characterise vitamin D status in toddlers, identify its determinants, and explore if vitamin D status was associated with bone mineralisation and lipid profile. Methods: We used cross-sectional data from 3-year-old children (n=323) living in Denmark (latitude: 55°N). Bone mineralisation (n=108) was measured by DXA. Blood samples were analysed for serum 25-hydroxyvitamin D (s-25(OH)D) by
LC–MS/MS, triacylglycerol, and total, low- and high density lipoprotein cholesterol.
Results: Mean±SD s-25(OH)D was 69±23 nmol/L, but varied with season.  During winter, 38% had inadequate s-25(OH) D (<50 nmol), whereof 15% had deficiency (<30 nmol/L); these numbers were only 7 and 1% during summer. In terms of status determinants, supplement use (66% were users) was associated with s-25(OH)D (P<0.001), whereas dietary vitamin D intake (median [25–75th percentile] of 1.3 [0.9–1.9] µg/d), sex, parental education, BMI, and physical activity were not. There were no associations between s-25(OH)D and blood lipids or bone measurements, using either unadjusted or adjusted regression models.
Conclusion: More than 1/3 of Danish toddlers had inadequate vitamin D intake during winter, but acceptable mean vitamin D status. In addition to season, supplement use was the main determinant of vitamin D status, which was, however, not associated with bone mineralisation or lipid profile. The results support recommendations of vitamin D supplements during winter at northern latitudes, but potential health effects need further investigation.