The body needs vitamin D to absorb calcium properly and to maintain bone and muscle health. We get most of the vitamin D we need from sunlight, but small amounts are also found in foods that include fatty fish and fortified margarine and milk.

Why is vitamin D important for health?

Vitamin D is important for general health and especially for bones. It is needed to make muscles move, for nerves to work properly, and for the immune system. Vitamin D is found in cells throughout the body.

Vitamin D’s main purpose is to help the body absorb calcium from food. If you don’t have enough vitamin D, you may develop soft, thin, brittle bones. This is called rickets in children and osteopaenia in adults. 

Together, vitamin D and calcium protect older people from developing osteoporosis.

How much vitamin D do I need?

Most people get as much vitamin D as they need from sunlight. If you get enough sunlight, you probably don’t need to worry about extra vitamin D in your diet. 

However, some people don’t get enough — even in a sunny country like Australia. Those most at risk are older people, especially if they live in residential care and don’t get outdoors very often. 

Others who might not get enough vitamin D from sunlight are those with darker skin, who cover up for cultural or religious reasons, who wear protective clothing, and who avoid the sun, for example because they have had skin cancer. Obese people, babies of mothers who don’t have enough vitamin D, and people with certain medical conditions or on some medicines may also be at risk of low vitamin D.

The amount of vitamin D you need varies with your age: 

• Everybody under the age of 50 needs 5 micrograms (200IU) each day (µg/day). A microgram is one millionth of a gram.
• People aged 51 to 70 need 10 µg/day (400IU).
• People 71 and over need 15.0 µg /day (600IU).

What are the best sources of vitamin D?

The best source of vitamin D is sunlight. Just spending a few minutes outdoors on most days of the week should give you all the vitamin D you need. 

In Australia, it is safe to go outdoors in autumn and winter with some skin uncovered, as long as the UV index is below 3. Being active while you’re outside — for example by walking or gardening — will boost your vitamin D levels. 

When the UV index is higher than 3, usually in spring and summer, most people need to protect themselves from the sun to prevent skin cancer. During these months, and if you live in parts of Australia where the UV index is above 3 all year, it’s usually safe to go outside without sun protection in early morning and late afternoon. 

Very few foods contain much vitamin D. The best food sources of vitamin D are fatty fish like salmon, herring and mackerel, and eggs.  In Australia, vitamin D is added to margarine. Some milk, soy drinks, breads and cereals may also be fortified with vitamin D. 

Should I take vitamin D supplements?

Just under 1 in 4 Australians has a vitamin D deficiency. People most at risk are the elderly and people with certain medical conditions such as liver disease and kidney disease, and those with problems absorbing food, including cystic fibrosis, coeliac disease and inflammatory bowel disease. Some medicines can also contribute to vitamin D deficiency.

A blood test can confirm whether you have a vitamin D deficiency. Your doctor may then recommend you take a vitamin D supplement along with a calcium supplement.

If you need vitamin D supplements, you will probably also be advised to spend more time outdoors and increase the amount of calcium in your diet. If your vitamin D is low due to a chronic medical condition, you may need to take supplements for the rest of your life. 

Vitamin D supplements come in many different strengths and dosages. They can be low dose — which you take every day — or high dose, which you take monthly or less frequently. 

Too much vitamin D can also cause health problems including weight loss, heart rhythm problems or damage to the heart, blood vessels and kidneys. It’s not possible to get too much vitamin D from sunlight, but if you are taking vitamin D supplements it’s important to speak to your doctor or pharmacist to check you are taking the right dose.