Why children and adults need vitamin D

Children need vitamin D for bone growth and development. So do babies developing in the womb. Vitamin D helps us absorb calcium.

Serious vitamin D deficiency can cause rickets, delayed motor development, muscle weakness, aches and pains, and fractures.

Vitamin D deficiency in adults has also been linked to osteoporosis, some cancers, heart disease and diabetes.

If women don’t get enough vitamin D during pregnancy, their children might develop neonatal hypocalcaemia (not enough calcium in the blood) or rickets later in childhood.

Vitamin D and sunlight

Your child needs sunlight on her skin for her body to make vitamin D. She gets about 80% of her vitamin D this way.

Scientists aren’t sure exactly how much sun Australian children need for good levels of vitamin D. But we do know that the amount of sun your child needs depends on where you live in Australia and the time of year.

It also depends a bit on your skin colour. People with naturally very dark skin need 3-6 times more sun to make vitamin D than the amount fair-skinned people need.

The picture below shows how much sun should be enough to help your child's body make vitamin D, without putting his skin at risk of sun damage.

How much sun is enough?
In Brisbane and Darwin, right through the year, a few minutes most days of the week should be enough.

In Canberra, Perth and Sydney:

  • in June and July, 2-3 hours per week should be enough
  • in summer, a few minutes most days of the week should be enough.

In Adelaide, Hobart and Melbourne:

  • from May to August, 2-3 hours per week should be enough
  • in summer, a few minutes most days of the week should be enough.

Be sun smart
No matter where you live in Australia, you have to be careful about how much sun your child gets on her skin. Too much sun can lead to sunburn, skin damage and even skin cancer. This is why it’s important to use sun protection.

During summer, especially between 10 am and 4 pm, make sure your child stays safe in the sun with sunscreen, a hat, sunglasses, clothing that keeps the sun off and access to plenty of shade.

To get more information and advice about how much sun is right for your child, speak with your GP.

Vitamin D and food

Most children won’t get enough vitamin D from food alone. But food with lots of vitamin D can add to the vitamin D your child gets from sunshine.

Foods naturally containing vitamin D include fresh fatty fish (salmon, herring, mackerel and sardines), liver, some mushrooms and egg yolks.

Some foods have vitamin D added to them. These include some low-fat dairy products, breakfast cereals and margarine. All infant formula contains vitamin D.

Your child can boost the benefits he gets from being out in the sun each day by doing some physical activity while he’s outside. This is because daily exercise helps your child’s body make vitamin D.

Vitamin D deficiency

Children might be at risk of vitamin D deficiency if they:

  • keep all their skin covered
  • spend most of their time indoors and don’t get much or any sun
  • have a condition affecting how the body controls vitamin D levels – for example, liver disease, kidney disease, conditions that cause problems with absorbing food (like coeliac disease or cystic fibrosis), and some medicines can affect vitamin D levels
  • have darker skin
  • have been breastfed for a long time and have a mother whose vitamin D is low.

Signs of vitamin D deficiency include rickets, delayed motor development, muscle weakness, aches and pains, and fractures.

Treating vitamin D deficiency

Talk with your GP if you’re worried about your child’s vitamin D levels, or you’re pregnant and think you might have low vitamin D.

Your GP can order a blood test, which is the best way to check vitamin D levels.

For mild deficiencies, your GP might say that your child needs to get a bit more sun.

If you or your child has a severe vitamin D deficiency, your GP might say you or your child should take vitamin D supplements, as well as getting more sun.

If you or your child can’t get more sun, the GP might say that taking vitamin D supplements is the best thing to do. You might take a vitamin D supplement in one large, single dose, or you might take a supplement for several weeks or months.

You can also talk to a dietitian about vitamin D supplements.

Solariums, sometimes called sunbeds or tanning beds, should never be used as a way to improve vitamin D levels or to treat vitamin D deficiency. Most states have a ban on commercial solarium operators. Solariums can cause skin cancer.

Vitamin D, pregnancy and breastfeeding

A baby’s vitamin D stores go up during development in the womb and go down after birth until the baby starts getting vitamin D from sunlight along with diet.

Breastfeeding babies don’t get much vitamin D from breastmilk, because breastmilk doesn’t have much. And if a breastfeeding mum has low vitamin D, she might not pass on enough vitamin D to her baby.

It’s recommended that breastfed babies with at least one other risk factor for low vitamin D, like dark skin, take a vitamin D supplement of 400 International Units IU or 10 micrograms (μg) a day. It’s a good idea to talk with your GP if you think your baby is at risk of vitamin D deficiency.

Infant formula has higher levels of vitamin D, so formula-fed babies don’t usually need a supplement.

Most cases of rickets in Australia are in children who have dark skin. This is because women who have dark skin – particularly those who wear covered clothing – have been found to have a high risk of vitamin D deficiency and don’t pass on adequate amounts of vitamin D to their children.