A dose-response, double-blind, randomised placebo-controlled trial to estimate the dietary requirement for vitamin D in male and female adolescents aged 14-18 years

INTERVENTION: Participants will be randomised to receive either 10mcg vitamin D, 20mcg vitamin D or a placebo Follow Up Length: 5 month(s) CONDITION: Topic: Primary Care; Subtopic: Not Assigned; Disease: All Diseases ; Nutritional, Metabolic, Endocrine PRIMARY OUTCOME: Serum 25‐hydroxyvitamin D concentrations; Timepoint(s): End of study (20 weeks after supplementation has begun) SECONDARY OUTCOME: Not provided at time of registration INCLUSION CRITERIA: 1. Male or female 2. Aged between 14 and 18 years 3. In good health 4. Written informed consent from the adolescent (and parent if required)