Vitamin D is important during the adolescent bone growth spurt, when ∼50% of bone mineral accrual occurs, influencing present and future bone health( 1 ). Commonly known as the ‘sunshine vitamin’, vitamin D is predominately obtained through cutaneous synthesis after exposure to ultraviolet B (UVB) radiation in sunlight, whilst a smaller percentage is obtained via the diet( 2 ). However, at northerly latitudes, UVB is scarce during the winter months, and there is little information focusing on the oral vitamin D intake of adolescents. The main objectives of this study were to estimate dietary vitamin D intake in UK white Caucasian adolescents, and to determine whether the values meet the World Health Organisation (WHO) recommendation of 5 μg/day( 3 ) or the more recent Institute of Medicine (IOM) guidance of 15 μg/day( 4 ). A further aim was to compare adolescent intake with that of previously collected data from an adult white Caucasian sample.
This was a 1 year observational study of 124 healthy white Caucasian adolescents aged 12–15 years recruited from six schools in Greater Manchester. Adolescents completed a daily dietary record of seven vitamin D-containing food categories and intake of supplements for one week in each season and the average daily vitamin D intake data was estimated. The vitamin D content of foodstuffs was determined from the 6th edition of McCance and Widdowson's The Composition of Foods( 5 ) and from food package labelling. Data were compared with those similarly obtained from the 4-season daily dietary records of an adult sample (20–60 years, n=109 completed) in Greater Manchester( 2 ). Adolescents (n=110 completed) showed little variation in vitamin D intake across the seasons. Their overall median (range) intake was only 1.92 (0.01–22.15) μg/day compared with 3.27 (0.02–27.38) μg/day in adults (P<0.01). As in the adult sample, oily fish was the main food contributor and vitamin D supplements were taken by a minority (25%) of adolescents.
We conclude that dietary vitamin D intake is very low amongst UK white adolescents and does not meet WHO recommendations( 3 ). It is much lower than specified in the recent IOM guidance for US and Canadian citizens( 4 ). Sun exposure levels and impact on vitamin D status are under study in this population, while the current data supports that within the adolescent population there is a risk that vitamin D requirements may not be met. This may have consequences for bone mineral accrual and subsequent bone health in later life.