Vitamin D is important for bone and muscle health. Vitamin D helps the body absorb calcium and phosphate from food, which are important for healthy and strong bones.
Only a few foods (some types of fish) naturally contain vitamin D, and it is hard to get enough vitamin D from food alone. Margarine, baby formula and some types of milk have added vitamin D, but most people only get about a quarter (or even less) of their vitamin D needs from food. Most
vitamin D is made in the skin when it is exposed to the sun.
As well as causing problems with bones and muscles, there is evidence that low vitamin D is linked to other health problems including: a higher risk of bowel cancer, heart disease, high blood pressure, stroke, problems with immunity (how the body fights infections) and
autoimmune diseases (including diabetes).
Signs and symptoms of low vitamin D (or vitamin D deficiency)
Many people with low vitamin D do not have symptoms, but some children with low vitamin D get bone and muscle pain. Very low vitamin D can lead to soft bones, causing rickets in children and a condition called osteomalacia (os-tee-oh-mah-lay-shee-ah) in adolescents and adults.
Rickets only occurs when children are growing – if a child has softer bones from low vitamin D, the bones can bend and cause 'bow legs' or 'knock knees', as well as other changes. See our fact sheet
Rickets.
Low vitamin D can cause low calcium, which can lead to muscle cramps in children. Low calcium can also cause seizures (convulsions or fits), particularly in young babies.
Children at risk of low vitamin D
- Children with very dark skin. The dark colour of their skin (melanin) acts as a natural sunscreen and increases the time they need in the sun to make vitamin D naturally.
- Children whose skin is rarely exposed to the sun e.g. those who stay inside or who wear covering clothing.
- Babies born prematurely.
- Breastfed babies who have one or more of the above risk factors. Breast milk is the best type of food for babies, but it does not contain much vitamin D. A baby will get their initial store of vitamin D from their mother; so, they are at risk of low vitamin D if their mother has low
vitamin D and/or if they have dark skin.
- Children with conditions affecting how the body absorbs and controls vitamin D, such as liver disease, kidney disease, problems absorbing food (e.g. cystic fibrosis, coeliac disease, inflammatory bowel disease) and some medicines (such as some epilepsy medicines).
When to see a doctor
Take your child to the GP if they show any symptoms of low vitamin D or low calcium.
Children who are at risk of low vitamin D should have a blood test three months after beginning to take supplements, to check their vitamin D level.
If your child has a seizure that lasts less than five minutes, take them to the nearest hospital emergency department as soon as the seizure has finished. If the convulsion lasts more than five minutes, call an ambulance.
Vitamin D treatment
Vitamin D tablets or mixtures can be low dose (taken daily) or high dose (taken monthly or less often). Tell your GP if your child is taking any vitamin D tablets/medicines, as too much vitamin D can also cause problems. It is important to know that there are lots of different types
of vitamin D tablets and mixtures, and some of them are very strong. It is always good to bring your child’s medicine when you see the GP so they can check what your child is taking.
Low vitamin D is a long-term problem. Once low vitamin D is treated, the aim is to make sure vitamin D levels stay normal. If your child is at risk of low vitamin D, they may need may need lifelong supplements, and you need to make sure they spend enough time outside (see below).
Children with low vitamin D also need enough calcium in their diet. Aim to give them two to three serves of dairy each day (one serve of dairy is equal to one glass of milk, one tub of yoghurt or one slice of cheese). If your child has a dairy allergy, talk to your doctor or nutritionist
about alternatives.
Sun exposure and vitamin D
For most people, low vitamin D can be prevented by spending time outside.
Most Australians with light skin get enough vitamin D through the sun during normal daily outside activities. Children with light skin are at risk of skin cancer and should always use sunscreen and recommended sun protection.
Most Australians with dark skin need a longer time in the sun to make enough vitamin D – up to six times as long as someone with light skin. The colour in their skin protects them against skin cancer, but they should still avoid sunburn. Children with dark skin do not usually
need to wear sunscreen during the autumn, spring or winter; however, hats and sunglasses are still important.
Visit the Bureau of Meteorology or use the free SunSmart app to find out the UV levels each day. During warmer months, when the UV-index rises above 3, incidental sun exposure (the exposure your child gets by being outside as part of their usual daily life) is often enough to maintain adequate vitamin
D levels.
It is safe to be outside without sun protection in the morning and late afternoon when the UV-index falls beneath 3 (unless at high altitude or near reflective surfaces, like snow). During times with low UV-index, children should spend time outdoors with areas of their skin uncovered.
Key points to remember
- Vitamin D is important for bone and muscle health.
- Most vitamin D is made in the skin when it is exposed to the sun. It is hard to get enough vitamin D from food alone.
- Children with very dark skin, whose skin is rarely exposed to the sun or who have certain medical conditions are at risk of low vitamin D.
- Children with low vitamin D need to take vitamin D supplements, spend enough time outside, and need to get enough calcium in their diet.
- Too much vitamin D can also cause problems.
For more information
Common questions our doctors are asked
Can you absorb vitamin D from the sun through a window?
The body needs certain rays of ultraviolet (UV) light to absorb vitamin D. Unfortunately, most glass windows block these particular rays, meaning not enough vitamin D will be absorbed.
My child wears sunscreen when outdoors due to their fair
skin, does that mean they will not absorb enough vitamin D?
It is quite hard to apply enough sunscreen to completely protect every part of the skin, therefore there are going to be areas where vitamin D can get absorbed. For this reason, sunscreen is unlikely to hamper vitamin D absorption through the skin.
Developed by The Royal Children's Hospital Immigrant Health department. We acknowledge the input of RCH consumers and carers.
Reviewed May 2018.
This information is awaiting routine review. Please always seek the most recent advice from a registered and practising clinician.
Kids Health Info is supported by The Royal Children’s Hospital Foundation. To donate, visit
www.rchfoundation.org.au.