Sources of vitamin D and determinants of serum 25-hydroxyvitamin D in Finnish adolescents

Abstract

Purpose: To study the intake and sources of vitamin D and determinants of serum 25-hydroxyvitamin D (S-25(OH)D) in Finnish adolescents.

Methods: We studied 265 adolescents (117 girls) aged 15-17 years attending 8-year examinations of the PANIC Study, assessed diet using food records and other lifestyle factors by questionnaires, and analyzed S-25(OH)D by chemiluminescence immunoassay and determinants of S-25(OH)D using multivariate linear regression.

Results: Mean (standard deviation) of total vitamin D intake from food and supplements was 19.2 (13.1) µg/d, and that of dietary vitamin D intake was 9.9 (5.4) µg/d. Milk fortified with vitamin D was the main dietary source of vitamin D, providing 45% of daily intake. Altogether, 29% of the adolescents used no vitamin D supplements and 25% did not meet the recommended total vitamin D intake of 10 µg/d. Mean (standard deviation) of S-25(OH)D was 62.0 (18.8) nmol/l, and S-25(OH)D was < 50 nmol/l in 29.5% of the adolescents. Vitamin D intake from supplements was the main determinant of S-25(OH)D (β = 0.465, p < 0.001), followed by consumption of milk products (β = 0.251, p < 0.001), consumption of meat products (β = 0.179, p = 0.002), travels to sunny countries (β = 0.178, p = 0.002), and average daylight time (β = 0.162, p = 0.004).

Conclusion: Most of the adolescents had vitamin D intake at the recommended level, although a fourth did not meet the recommended total vitamin D intake of 10 µg/d and almost a third had S-25(OH)D < 50 nmol/l. More attention should be paid to the sufficient intake of vitamin D in adolescents who do not use vitamin D supplements or fortified milk products.

Trial registration: ClinicalTrials.gov: NCT01803776, registered March 3, 2013.

Keywords: 25-Hydroxyvitamin D; Adolescents; Diet; Fortification; Supplements; Vitamin D.