UK Adolescents Need More Vitamin D

19 Oct 2016 --- Levels of vitamin D is inadequate among UK adolescents, according to a new study. The study, from the University of Surrey’s Department of Nutritional Sciences in collaboration with colleagues from the University of Copenhagen and University College Cork, has also identified the intake needed by adolescents in order to maintain adequate serum vitamin D levels during the wintertime. 

Vitamin D plays an essential role in bone mineralization and skeletal development, as it optimizes calcium absorption. Since most rapid bone growth occurs during the adolescent years, it is vital that teenagers have sufficient levels of vitamin D in order to achieve peak bone mass by late adolescence. It’s also thought that this helps to reduce age-related bone loss in later life.

The study looked at adolescents particularly vulnerable to vitamin D deficiency, as previous studies have shown that vitamin D levels decrease during puberty.

With adolescents less likely to spend time outdoors than younger children, they experience less exposure to the sun, which is how humans naturally obtain vitamin D. Low vitamin D levels are also a problem at northern latitudes during the winter months when the sun is not sufficient to make vitamin D within the body, so dietary intakes become more important.

However, getting the right amount of vitamin D from food can also be a challenge. Lead author, Dr Taryn Smith from the University of Surrey told NutritionInsight: "Currently in the UK it is very difficult to obtain adequate dietary vitamin D intakes from food sources alone due to limited foods being a rich source of vitamin D."

"Good sources include oily fish and eggs and although meat contains small amounts of vitamin D, it is one of the biggest contributors to vitamin D intakes due to its frequent consumption."

Smith explained, "While in the UK some foods are fortified with vitamin D to help increase vitamin D intakes through food, including breakfast cereals and margarines/fat spreads, more widespread fortification of foods is required"

"For example, in the USA, Canada and Finland, milk is routinely fortified with vitamin D and these populations generally have higher intakes than seen in the UK. There are ongoing studies to help determine if we can do this with different food sources."

The study looked at 110 white male and female adolescents who were either given varying levels of vitamin D3 supplements or a placebo supplement for a 20 week period during winter.

The results showed that vitamin D intakes of between 10 and 30 ug/day are required to maintain an adequate level of vitamin D and avoid vitamin D deficiency.

Commenting on the findings, Smith explained, “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.”

The study forms part of a four-year EU-funded project, ODIN, which aims to investigate safe and effective ways of improving dietary vitamin D intakes through food fortification and bio-fortification.

Smith explained, “The ODIN project is investigating ways of improving vitamin D intake through the diet, and since it is difficult to obtain vitamin D intakes of over 10 ug/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."

Smith believes that along with diet changes, encouraging children and adolescents to do more outdoor activity and spend less time indoors, sedentary, could help increase vitamin D levels, saying, "While this will increase sun exposure and therefore improve vitamin D levels, it will also contribute to increasing physical activity levels in this age group and also help to tackle the childhood obesity problem seen in the UK"

Although vitamin D levels are generally low, Smith explained that due to the vast amount of scientific literature and studies over recent years, as well as its appearances in the media, more people are aware of vitamin D and its importance for bone health. However, she added, "It is important that the media and companies promote this correctly and interpret research study data accurately as what can often be seen in nutrition research is a misinterpretation of data and this leads to public confusion."

The key findings will be presented by lead author Dr Taryn Smith of the University of Surrey at the National Osteoporosis Society Conference, due to be held from 7 to 9 November 2016 in Birmingham. 

by Hannah Gardiner