Vitamin D is important for bone health because it helps absorb calcium. It also plays a role in:
- Supporting growth and maintenance of the skeleton
- Regulating calcium levels in the blood
Vitamin D and sunshine
For most Australians, the main source of vitamin D is from exposure to sunlight. Vitamin D is produced when our skin is exposed to ultraviolet B (UVB) light from the sun. The amount of sun exposure required to produce adequate levels of vitamin D is relatively low.
However many Australians do not have adequate vitamin D levels, especially during winter. Sun exposure times will vary based on the season, location in Australia and skin type and amount of skin exposed.
It is important to balance the need for sun exposure for vitamin D, while at the same time avoiding the risk of skin damage.
In summer, exposure is best at mid-morning or mid-afternoon outside peak UV times. In summer, most Australian adults will maintain adequate vitamin D levels during typical day-to-day outdoor activities. When the UV index is above 3 (all states during summer and some states in winter months), you should use sun protection measures if you are outdoors for more than a few minutes.
In winter, longer exposure times are needed preferably around midday. In autumn or winter, in states where the UV index is below 3 for most of the day sun protection isn't needed.
You can check the UV index via the Cancer Council Website or myuv.com.au.
Recommended sun exposure based on location
Vitamin D deficiency
Vitamin D deficiency is common in Australia with over 30% of adults having a mild, moderate or even severe deficiency. Low vitamin D levels can:
- Lead to bone and joint pain
- Increase the risk of falls and bone fracture in older people
- Result in rickets (when very serious)
- Impact on unborn children in mothers with vitamin D deficiency
Groups at risk of vitamin D deficiency
Only people at risk of vitamin D deficiency may need vitamin D levels checked, as determined by a doctor. You may be at risk of vitamin D deficiency if you are:
- Elderly and housebound or in residential care
- Naturally dark skinned (darker skin reduces the penetration of UV light)
- Avoiding the sun for skin protection or due to medical advice for other medical reasons
- Covering your body for cultural or religious reasons
- Affected by other medical conditions that can impact on your ability to absorb / process vitamin D
- Babies of vitamin D deficient mothers
Vitamin D testing
Vitamin D levels can be determined with a blood test. Your doctor will determine if you require a test, based on your general level of sun exposure, medical history and review of risk factors. Vitamin D levels are likely to change throughout the year with concentrations being highest in late summer and lowest at the end of winter.
Recommended vitamin D levels
As a general guide, Osteoporosis Australia recommends most people should have a vitamin D level of at least 50 nmol/L at the end of winter, which means people may have levels 10 – 20 nmol/L higher during summer (60-70 nmol/L).
Vitamin D supplements
For people with low vitamin D levels (which may be in the range of mild or moderate to severe) a supplement may be required. Most vitamin D supplements are ‘D3’ and the dose on the product is shown in International Units (IU). Vitamin D supplements are available as tablets, capsules, drops or liquid. Your doctor will advise you on the appropriate dose for your needs and your pharmacist can also provide general advice on vitamin D supplements.
As a general guide only, Osteoporosis Australia recommends the following doses of vitamin D:
Vitamin D and food
Food cannot provide an adequate amount of vitamin D and most people are reliant on sun exposure to reach recommended levels.
A limited number of foods contain small amounts of vitamin D such as oily fish like salmon, tuna, mackerel and herring, liver, egg yolks and some fortified products.