The role of Vitamin D

Vitamin D

What is it and what is it important for?

Vitamin D is a nutrient that is naturally present in very few foods and is added to some synthetically. We get most of our vitamin D through sun exposure. It’s important to maintain strong bones, and it does this through helping the body absorb calcium (a main building block of our bones). Vitamin D also has an important role to play in our nerves and immune system, which needs vitamin D to fight off bacteria and viruses.

 Who’s at risk of deficiency?

Vitamin D deficiency is common both in the UK and Europe population. Daily supplementation is recommended in the UK winter months from around late September to March/early April.

Very few foods in nature contain vitamin D. The flesh of fatty fish (such as salmon, tuna, and mackerel) and fish liver oils are among the best sources. Small amounts of vitamin D are found in beef liver, cheese, and egg yolks. Milk is fortified with Vitamin D in the US.

High risk groups in the UK include; older adults, people with dark skin, people with limited sunlight exposure.

UK guidelines for Vitamin D supplementation:

Supplementation typically comes in 2 forms, D2 (ergocalciferol) and D3 (cholecalciferol). Both forms have been identified to effectively raise serum 25(OH)D levels.

UK guidelines

  • Aged 1yr and above – 10 µg/day (400 IU/day). This includes pregnant and lactating women and population groups at increased risk of deficiency.

Safe limit: No more than 100 ug/day, and not more than 50 ug/day (2000 IU/day) in those aged 1-10 years.

  • Babies up to the age of 1 year need 8.5 to 10 micrograms (ug) (or 340-400IU) of vitamin D a day if they are breastfed. Formula-fed babies shouldn’t be given a vitamin D supplement until they’re having less than 500ml (about a pint) of infant formula a day, as infant formula is fortified with vitamin D.

Safe limit: No more than 25 ug/day (1000 IU/day) should be provided.


Taking too many vitamin D supplements over a long period of time can cause too much calcium to build up in the body (hypercalcaemia). This can weaken the bones and damage the kidneys and the heart. Your body doesn’t make too much vitamin D from sun exposure, but always remember to cover up or protect your skin if you are exposed to the sun for long periods of time to reduce the risk of sun damage and skin cancer.

Some people have medical conditions or are taking medications conditions that mean they may not be able to safely take as much. If in doubt, you should consult your doctor. If your doctor has recommended you take a different amount of vitamin D, you should follow their advice.



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