Linking vitamin D status,executive functioning and self‐perceived mental health in adolescents through multivariate analysis: A randomized double‐blind placebo control trial

The aim of the present randomized double‐blind placebo control trial was to investigate if vitamin D supplementation had an effect on vitamin D status, executive functioning and self‐perceived mental health in a group of Norwegian adolescents during winter time. Fifty adolescents were randomly assigned into an intervention group (vitamin D pearls) or a control group (placebo pearls). Before (pre‐test in December/January) and after (post‐test in April/May) the intervention period the participants were exposed to a test procedure, consisting of blood draw, completion of cognitive tests (Tower of Hanoi and Tower of London), and the Youth Self‐report version of the Child Behavior Checklist. Multivariate data analysis showed that participants with low vitamin D status scored worse on the Tower of London tests and the more difficult sub‐tasks on the Tower of Hanoi tests. They also had a tendency to report higher frequency of externalizing behavior problems and attention deficit. At pre‐test, the overall mean vitamin D status measured as 25‐hydroxy vitamin D was 42 nmol/L, defining deficiency (Intervention group = 44 nmol/L, Control group = 39 nmol/L). However, vitamin D supplementation caused a significant increase in vitamin D status resulting in a sufficient level in the Intervention group at post‐test (mean 62 nmol/L). The results also revealed that the intervention group improved their performance on the most demanding sub‐tasks on the ToH. Overall, the study indicates that vitamin D status in adolescents may be important for both executive functioning and mental health.