Vitamin D is known as the “sunshine vitamin” because your body produces it when exposed to natural sunlight. It is also an essential nutrient for calcium absorption and overall bone health.

Explore the resources below to learn how vitamin D and calcium work together to help build and maintain strong, healthy bones throughout life.

What is Vitamin D?
Vitamin D is one of many nutrients needed in our body to stay healthy. It is essential for the development and maintenance of bone health. You can get vitamin D from exposure to the sun, from your diet (certain foods) and from supplements. Vitamin D is a fat-soluble vitamin, the vitamin D your body produces and consume in your diet is stored in fat tissue for later use.

Vitamin D is a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and multiple other biological effects. In humans, the most important compounds in this group are vitamin D₃ and vitamin D₂

How Much Vitamin D do I Need?2
Most Australian’s receive their Vitamin D from exposure to the sun. People with moderately fair skin need sun exposure of 6-7 minutes mid-morning or mid-afternoon on most days during the Australian summer to maintain adequate vitamin D levels. Up to 30 minutes exposure will be required during winter, depending on where you are located.

  • Vitamin D is a hormone that controls calcium levels in the blood. It is needed for strong bones, muscles and overall health.

  • The sun’s ultraviolet radiation (UV) is the main cause of skin cancer and the best natural source of vitamin D.

  • Vitamin D levels change naturally with the seasons. How much UV exposure a person needs depends on the time of year, UV levels, their skin type and their existing vitamin D levels.

  • Being physically active outdoors will help make vitamin D.

  • The body can only absorb a limited amount of vitamin D at a time. Spending extra time in the sun won’t increase vitamin D levels – but will increase your risk of skin cancer.

  • Some people are at increased risk of low vitamin D – this includes people with naturally very dark skin and people who have very low exposure to sunlight.

Groups At Risk3
Adult group at high risk of low levels of Vitamin D are as follows:

  • Older and disabled people in low-level and high-level residential care

  • People with darker skin

  • People with medical conditions or medications affecting vitamin D metabolism

 

Vitamin D is important for strong bones, muscles and overall health. Ultraviolet (UV) radiation from the sun is necessary for the production of vitamin D in the skin and is the best natural source of vitamin D. 

UV radiation from the sun is also the main cause of skin cancer. 

Small amounts of the vitamin D you need can be obtained through food (about 5 – 10 per cent). Fish and eggs naturally have some vitamin D, while margarine and some milks have added vitamin D.

The body can only absorb a limited amount of vitamin D at a time. Spending extra time in the sun will not increase vitamin D levels – but will increase your risk of skin cancer.
Daily exercise also assists with the body’s production of vitamin D.

Health effects of low vitamin D

Vitamin D deficiency does not always have obvious symptoms but without treatment there can be significant health effects. These can include bone and muscle pain, and softening of the bones – such as rickets (in children) and osteomalacia (in adults). 

Some people are at greater risk of vitamin D deficiency, including:

  • people with naturally very dark skin –this is because the pigment (melanin) in dark skin doesn’t absorb as much UV radiation

  • people who avoid the sun due to previous skin cancers, immune suppression or sensitive skin and those people who have limited sun exposure, such as nightshift workers

  • people who wear covering clothing or concealing clothing

  • people who spend a long time indoors – such as those who are housebound or institutionalised

  • people who are obese 

  • people who have a disability or a disease that affects vitamin D metabolism, such as end stage liver disease, renal disease and fat malabsorption syndromes such as cystic fibrosis, coeliac disease and inflammatory bowel disease

  • people who take medication that affects vitamin D metabolism

  • breast-fed babies of vitamin D deficient mothers (formula milk is fortified with vitamin D)

If you think you may be at risk of vitamin D deficiency, talk to your GP for advice. Your GP may recommend taking a vitamin D supplement. 

Overexposure to UV is never recommended, even for people who have vitamin D deficiency.

Vitamin D and food

There are small amounts of vitamin D in some foods such as fish, eggs and UV-irradiated mushrooms, but it is difficult to obtain enough vitamin D from diet alone. Most people only get five to 10 per cent of their vitamin D from food. Margarine and some types of milk have added vitamin D.

Vitamin D and safe sun exposure

UV levels vary depending on the time of year, and the amount of sun exposure you need varies accordingly. 

The ‘daily sun protection times’ indicate when the UV level is forecast to be three or above. During these times, people are recommended to use a combination of sun protection measures (sunscreen, hat, protective clothing, sunglasses and shade). 

Check the free SunSmart app or the Bureau of Meteorology website for daily sun protection times for your location.

If you are concerned about your vitamin D levels, seek advice from your GP.

Your GP may recommend vitamin D supplements, which should be taken strictly as directed. Once low vitamin D is treated, the aim is to maintain normal vitamin D levels.

References: 

1. NPS Medicine Wise (2014).Vitamin D Tests and Deficiency. Available at https://www.nps.org.au/__data/assets/pdf_file/0010/229663/Vitamin-D-tests-and-deficiency.pdf [Accessed 16 March 2016]

2. Nutrient Reference Values (2014), Calcium. Available at: https://www.nrv.gov.au/nutrients/calcium [Accessed 20 January 2016]

3. Osteoporosis Australia (2013), Vitamin D position statement – Reviewed October 2013. Available at: http://www.osteoporosis.org.au/sites/default/files/files/Vit%20D%20Position%20Statement%2010%202013%20V2(1).pdf [Accessed 22 January 2016]