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1/ Vitamin D is an essential nutrient that contributes to healthy, strong bones and helps to control the amount of calcium in the blood. It is fat soluble and is stored in adipose tissue when dermal synthesis and dietary intake exceed daily requirements (this is important as, during the winter months, these stores are used when the critical wavelength in sunlight is insufficient for the dermal synthesis of vitamin D in the body).


2/ Recent evidence suggests that vitamin D may also help in the prevention of many other diseases. Adequate levels of vitamin D are also associated with other health benefits

such as immunity and cardiac function.


3/ Low levels of vitamin D is associated with a range of diseases including osteoporosis, cardiovascular disease, multiple sclerosis and mental health issues.1,2


4/ Although most of this evidence has been demonstrated in adults, these guidelines will focus on vitamin D and role in bone health in school age children.


Where does vitamin D come from?


5/ The main natural source of vitamin D in humans is from the dermal synthesis of pre-vitamin D following exposure to sunlight.3


6/ In the UK, vitamin D can only be made in the skin by the action of UV sunlight during the summer-time, as sunlight of the critical wavelength only reaches the UK between approximately April / May and September / October depending on how far north the person lives.


7/ Further, this critical wavelength light will not pass through glass and is most effective during the middle of the day when the sun is highest in the sky; on cloudy days or when there is air pollution, less vitamin D will be synthesised.


8/ Spending excessive time indoors and wearing clothes that cover most of the skin will affect the synthesis, or use of sunscreens.


9/ As darker skins require more time for the light to synthesise the same amount of vitamin D as light skins, those of Asian, African and Middle Eastern ethnic origin are more likely to have lower vitamin D levels than those of Caucasian ethnic origin.1,4,6,7,8


10/ Vitamin D is found naturally in a few foods such as oily fish – sardines, salmon, mackerel, pilchards and tunaalthough it is thought that less than 10% of vitamin D is derived from food alone.4


11/ A few foods are fortified with small amounts of vitamin D – margarine, some breakfast cereals – and there are smaller amounts in red meat and egg yolks. In some countries, such as

Finland, Canada and the USA, a wider range of commonly consumed foods such as fresh cow’s milk, other dairy products and some fruit juice are fortified with vitamin D.

12/ Whether ingested orally or made in the skin under the action of UV light, vitamin D is converted to the active metabolite via the liver and kidneys.


Implications for children’s bone health


13/ Vitamin D deficiency impairs the absorption of calcium and phosphorus and can thus lead to poor mineralisation of the bones.


14/ Adolescence, when there is rapid growth, is a critical developmental period for bone health. Although rickets is most commonly observed during infancy, it can also occur during the pubertal growth spurt and adolescence.


15/ Insufficient vitamin D during this time can also affect bone mineral density and lead to children and adolescents not achieving their full potential of peak bone mass.


16/ Vitamin D deficiency can also cause muscle weakness at any age.


17/ While deficient levels of vitamin D are usually asymptomatic, young children may present with classic features of bow legs and swollen wrists, and have had delayed walking because of a proximal myopathy. Severe cases of rickets may exhibit bone pain or deformities.


18/ Teenagers may present with aches and pains in their legs and have muscle weakness.1

They may also have bone changes of rickets or osteomalacia.


What is a low vitamin D level?


19/ There are many debates about the ideal vitamin D blood level. Deficiency has been defined as a blood level of 25 hydroxyvitamin D below 25 nmol/L; there is consensus that optimal levels lie above 50 nmol/L.9

20/ Some laboratories define a “deficiency of vitamin D” as levels below 25, or even 30, and an “insufficiency of vitamin D” as a level between either 25 or 30 and 50 or 70 nmol/L.


21/ School doctors may wish to check with their local biochemistry laboratory as to what is defined as “deficiency” or “insufficiency”, vitamin D test costs around £20 on the NHS.  And you can ordered via LOC at a discounted cost of £35.


22/ In the latest report of the Scientific Advisory Committee on Nutrition (SACN) on “Vitamin D and Health” (July 2016), the current threshold of a vitamin D level of 25 nmol/L has remained as the level below which the risk of vitamin D deficiency increases; however, while this is not a clinical threshold diagnostic of disease, it is indicative of increased risk or poor musculoskeletal health.8


How common is vitamin D deficiency in school age children?

23/ Public Health England published data in 2014 showing that in the winter months 30-40% of all age groups in the general population are classed as vitamin D deficient and that even towards the end of the summer 13% of adolescents remain deficient (compared to 8% of adults).


24/ The latest data show the population by age with a plasma vitamin D level of < 25 nmol/L, in the 11 to 18-year age group, is 20-24% of the total.


Which school age children might be at higher risk of vitamin D deficiency?


25/ Children at a higher risk of vitamin D deficiency might be: –

  • Those with an increased need for vitamin D
  • Adolescents10
  • Obese children
  • Those who have less sun exposure on bare skin
  • Living in a Northern latitude, especially above 50 degrees of latitude, as in the UK
  • Those who are darker skinned, especially those of Asian or African ethnic origin.1,4,6,7,10
  • Those who wear very concealing clothes.10
  • Those who use an excessive amount of sunblock. (* see 26 below)
  • Those who rarely go outdoors.10
  • Those who will get less vitamin D from their diet (remembering that only 10% is obtained this way)
  • Vegetarians, and especially vegans 5,10
  • Those children who have exclusion diets e.g. those with a dairy allergy
  • Those children with any malabsorption state
  • Those with liver or renal disease
  • Those taking certain drugs e.g. some anticonvulsants


26/ *A Consensus Vitamin D position statement has been prepared by the British Association of Dermatologists, Cancer Research UK, Diabetes UK, the Multiple Sclerosis Society, the National Heart Forum, the National Osteoporosis Society and the Primary Care Dermatology Society and is as follows:

“Vitamin D is essential for good bone health and for most people sunlight is the most important source of vitamin D. The time required to make sufficient vitamin D varies according to a number of environmental, physical and personal factors but is typically short and less than the amount of time needed for skin to redden and burn. Enjoying the sun safely, while taking care not to burn, can help to give the benefits of vitamin D without unduly raising the risk of skin cancer. Vitamin D supplements and specific foods can help to keep up sufficient levels of vitamin D, particularly in people at risk of deficiency.

However, there is still a lot of uncertainty around what levels qualify as “optimal” or “sufficient”, how much sunlight different people need to meet a given level of vitamin D, whether vitamin D protects against chronic diseases such as cancer, heart disease and diabetes, and the benefits and risks of widespread supplementation.”

27/ This guidance was endorsed by NICE in it is 2016 guideline, “Sunlight exposure: risks and benefits” (NG34) 12 


How to prevent and treat vitamin D deficiency in school age children


28/ Identify those at higher risk and look for symptoms and signs.10


No risk factors                                                  No investigations needed

Give lifestyle advice** and consider prevention


Risk factors but no symptoms                      Lifestyle advice** and start prevention.


Risk factors and symptoms or signs            Do blood tests and / or X-rays.

Start treatment and consider long term

prevention, at least until the child stops



29/ ** Lifestyle advice:

  • Increasing sun exposure safely.
  • Encouraging outdoor activities.
  • Advising about diet and the use over-the-counter supplements.


30/ ONLY test vitamin D status if someone has symptoms of deficiency or is at high risk.10


To supplement or not?


31/ The SACN which advises Public Health England and other government bodies, made a detailed statement which was published in July 2016 and which was derived from a lengthy scientific consultation based on current evidence. (See the 304-page pdf. document entitled Vitamin D and Health”)8


32/ In a change to their previous advice, SACN now recommends an RNI (reference nutrient intake) for vitamin D of 10 micrograms / day (= 400 IU) throughout the year for everyone in the general UK population aged 4 years and over.


33/ SACN recommends this amount to be applicable throughout the year as a precautionary measure to cover those population groups in the UK identified as being at risk of having a serum vitamin D level of < 25nmol/L, as well as unidentified individuals in the population who are at risk of having a serum concentration of < 25 nmol/L in the summer.


34/ However, many specialists working in this field remain concerned about the rapidly increasing number of vitamin D tests being requested and the prescribing of supplements on NHS prescriptions as these supplements are readily available in chemists, health food shops and supermarkets.


Use vitamin D supplements in prevention and maintenance 11,13


35/ Use colecalciferol (vitamin D3) – preferable to ergocalciferol (vitamin D2) because of the longer half-life of vitamin D3.


36/ Many over the counter multivitamin products contain far too low a dose of vitamin D.


Doses of vitamin D


37/ Note that doses can be confusing as they may be expressed as International Units (IU) or as micrograms of vitamin D – where 10 micrograms of vitamin D = 400 International Units.


38/ Standard prevention dose of vitamin D: – 

  • From age 4 upwards: 400 units daily (10 micrograms) throughout the year


39/ Standard treatment dose for vitamin D deficiency with symptoms: –

  • Up to age 12: 6000 units daily for between 4-8 weeks
  • 12-18 years: 10,000 units daily for between 4-8 weeks


40/ The same effect is achieved by multiplying the dose by seven and giving it weekly.


41/ If compliance is an issue in older children, some authorities recommend a single dose (multiply the daily dose by 30).11


42/ Need to check that the child has a sufficient dietary calcium intake and that maintenance vitamin D doses follow the treatment dosing and is continued long term, at least until the child stops growing. (For maintenance, use the same dose as for prevention – as above).


Which vitamin D preparation to use? 13


43/ With regard to over-the-counter preparations for prevention and maintenance, only a few have reliable quality control standards, such as: –

  • Boots Vitamin D tablets 10 micrograms. 90 tablets. Cost approx. £2.19 for three months.


44/ Only the following, available on prescription, are licensed for prevention: –

  • Desunintablets (colecalciferol) 800IU (20micrograms). NHS cost £3.40 for 30 days.
  • Fultium-D3capsules 800IU (20 micrograms).
  • InVita D3oral solution and drops 2,400 IU/ml.


45/ Preparations available on prescription for the treatment of vitamin D deficiency are listed in the BNF.10

46/ Note that vitamin D toxicity from excessive vitamin D is very rare.14




  1. Scientific Advisory Committee on Nutrition (2003). Vitamin D deficiency in Children. http://www.SACN.gov.uk/pdfs/smcn_03_02.pdf


  1. Wagner, CL and Greer, FR (2008): ‘Prevention of Rickets and Vitamin D Deficiency in Infants, Children and Adolescents’. Pediatrics 122:1142-1152


  1. Scientific Advisory Committee on Nutrition (2007). Update on Vitamin D. http://www.SACN.gov.uk/pdfs/SACN_position_vitamin_d_2007_05_07.pdf


  1. National Diet and Nutrition Survey (May 2014): results from Years 1 to 4 (combined) of the rolling programme for 2008 and 2009 to 2011 and 2012. Public Health England and Food Standards Agency.


  1. Alder Hey Children’s NHS Foundation Trust (April 2015)

Vitamin D Deficiency and Nutritional Rickets: Supplementation and Treatment in Infants and Children.



  1. Kehler, L et al (2012), “Vitamin D deficiency in children presenting to the emergency department: a growing concern”.



  1. Shaw, N J and Pal, B R (2002), “Vitamin D deficiency in UK Asian families: activating a new concern”.

Arch. Dis. Child. 86:147-149


  1. Scientific Advisory Committee on Nutrition (2015): “Vitamin D and Health”.



  1. British Paediatric and Adolescent Bone Group (2012). Position statement on Vitamin D. Letter to the BMJ.



  1. NICE Guidelines Public Health Guideline “Vitamin D; increasing supplement use in at-risk groups”. Published 26 November 2014.


  1. Royal College of Paediatrics and Child Health (RCPCH). “Guide for Vitamin D in Childhood”. pdf document. Published October 2013. http://www.RCPCH.ac.uk/system/files/protected/page/vitdguidancedraftspreads%20FINAL%20for%20website.pdf


  1. NICE Guideline. (NG34). Sunlight exposure: risks and benefits. February 2016.



  1. Prevention of vitamin D deficiency. More, J. British Journal of Family Medicine: Vol 4 Issue 2 March 2016. P28-33.



  1. US National Institutes of Health. Office of Dietary Supplements. (Updated February 2016).

Fact Sheet for Health Professionals. “Vitamin D”



This article has been written by Dr F Lyons