A new study led by the University of Surrey, and published in the American Journal of Clinical Nutrition, finds high prevalence of vitamin D inadequacy in 14 to 18 year olds at a time of the year when vitamin D levels should be at their peak (post-summer). The research identifies the level of vitamin D intake needed by adolescents to avoid vitamin D deficiency and ensure adequacy.
Teenagers spend too much time indoors
Research conducted in the United Kingdom, Denmark and Ireland has found that there is a high level of vitamin D deficiency among adolescents. The research suggests this may be due to the fact that adolescents spend less time outdoors and therefore leading to minimal exposure to the sun than younger children. The study has determined the minimal intake required in order to maintain advised vitamin D levels throughout the winter.
Northern hemisphere experiences lower sunlight levels
This problem is compounded by the fact that countries in the northern hemisphere have considerably lower sunlight levels compared to those in the southern hemisphere, especially in the winter months. This means more emphasis needs to be given to the nutritional intake of vitamin D, especially during winter months when the number of daylight hours are less.
14-18 age range considered most vulnerable
Vitamin D deficiency has been widely reported in teens across Europe, in fact in countries across the globe. Those that fall into the 14-18 age range are considered to be most vulnerable to vitamin D deficiency because bones grow more rapidly during these teenage years therefore sufficient levels of vitamin D are vital in order to achieve optimum bone mass by late adolescence and to prevent age related bone loss in later years.
Lead author Dr Taryn Smith of the University of Surrey comments "The research has found that adolescence, the time when bone growth is most important in laying down the foundations for later life, is a time when vitamin D levels are inadequate."
Intake recommendations are not universally agreed
Unfortunately there is no universally agreed intake level for vitamin D. The UK's Scientific Advisory Committee on Nutrition (SACN), and the UK Government propose a vitamin D intake of 400iu per day to maintain an adequate level of vitamin D in the body.
In 2012 the European Food Safety Authority (EFSA) could not find any evidence that adolescents had a lower tolerance for vitamin D compared to adults so an upper intake level (UL) of 4000iu for teenegers aged 11-17 was proposed.
In the trial 110 teenagers from the UK were randomly assigned to receive a placebo, 400iu or 800iu of vitamin D3 daily for 20 weeks during winter time.
Intake of approximately 1200iu per day recommended
The results of the trial indicated that a daily vitamin D intake of between 1200iu were required to maintain an adequate level of vitamin D and avoid the problem of deficiency.
This study forms part of a bigger four year EU funded project called ODIN (Food-based solutions for Optimal vitamin D Nutrition and health through the life cycle; http://www.odin-vitd.eu/) which aims to investigate safe and effective ways of improving dietary vitamin D intakes through food fortification and bio-fortification.
Dr Taryn Smith explains "The ODIN project is investigating ways of improving vitamin D intake through diet. Since it is difficult to obtain vitamin D intakes of over 400iu per day from food sources alone, it is looking at ways of fortifying our food to improve the vitamin D levels of the UK population as a whole."