Determinants of serum 25-hydroxyvitamin D concentration in Finnish children: the Physical Activity and Nutrition in Children (PANIC) study

We studied vitamin D intake, serum 25-hydroxyvitamin D (S-25(OH) D) concentration, determinants of S-25(OH) D and risk factors for S-25(OH) D <50 nmol/l in a population sample of Finnish children. We studied 184 girls and 190 boys aged 6-8 years, analysed S-25(OH) D by chemiluminescence immunoassay and assessed diet quality using 4-d food records and other lifestyle factors by questionnaires. We analysed the determinants of S-25(OH) D using linear regression and risk factors for S-25(OH) D <50nmol/l using logistic regression. Mean dietary intake of vitamin D was 5.9 (SD 2.1) mu g/d. Altogether, 40.8% of children used no vitamin D supplements. Of all children, 82.4% did not meet the recommended total vitamin D intake of 10 mu g/d. Milk fortified with vitamin D was the main dietary source of vitamin D, providing 48.7% of daily intake. S-25(OH) D was <50nmol/l in 19.5% of children. Consumption of milk products was the main determinant of S-25(OH) D in all children (standardised regression coefficient beta=0.262; P<0.001), girls (beta=0.214; P=0.009) and boys (beta=0.257; P=0.003) in multivariable models. Vitamin D intake from supplements (beta= 0.171; P=0.035) and age (beta=-0.198; P=0.015) were associated with S-25(OH) D in girls. Children who drank >= 450 g/d of milk, spent >= 2.2 h/d in physical activity, had >= 13.1 h/d of daylight time or were examined in autumn had reduced risk for S-25(OH) D <50nmol/l. Insufficient vitamin D intake was common among Finnish children, one-fifth of whom had S-25(OH) D <50 nmol/l. More attention should be paid to the sufficient intake of vitamin D from food and supplements, especially among children who do not use fortified milk products.