UV radiation from the sun causes skin cancer, but it is also the best natural source of vitamin D, which is needed to develop and maintain strong and healthy bones.
In Australia we need to balance the risk of skin cancer from too much sun exposure with maintaining vitamin D levels.
What is vitamin D and why is it important?
Vitamin D forms in the skin when it is exposed to UVB radiation from sunlight. Some foods, such as oily fish and eggs also contain small amounts of vitamin D, while margarine and some types of milk have added vitamin D. However, food only makes a small contribution to the body’s overall vitamin D levels and it is difficult to get enough from diet alone.
We need vitamin D to maintain good health, in particular to keep bones and muscles strong and healthy.
How much sun do we need for vitamin D?
When the skin is exposed to UV radiation from the sun, vitamin D is formed through a series of processes that start in the skin.
The amount of sunlight you need for vitamin D depends on several factors, including age, the UV level, your skin type and your lifestyle. UV levels vary across Australia, so the time you need to spend in the sun will be determined by your location, the season, the time of day, cloud coverage and the environment.
The body can only absorb a limited amount of vitamin D at a time. Extended periods of time in the sun does not increase your vitamin D levels, but they do increase your skin cancer risk.
When the UV Index is 3 or above (August–May in South Australia), incidental sun exposure—such as walking from the office to get lunch or hanging out the washing—is enough for most people to produce the required vitamin D levels, even when wearing sun protection.
In June and July, when the UV Index typically falls below 3 in southern states, we recommend spending time outdoors in the middle of the day with some skin uncovered on most days of the week to support vitamin D production. Being physically active (e.g. gardening or going for a brisk walk) may also help to increase vitamin D levels.
If I protect myself from the sun, will I still get enough vitamin D?
Sensible sun protection when UV reaches 3 and above does not put people at risk of vitamin D deficiency. When sunscreen is tested in laboratory conditions it is shown to block vitamin D production, however regular use in real life has been shown to have little effect on vitamin D levels. This is probably because sunscreen doesn’t block 100 per cent of UV radiation so your skin is still exposed to small amounts of UV, even when sunscreen is applied liberally. People who use more sunscreen also spend more time in the sun, so naturally they will have higher vitamin D levels.
When do I need sun protection?
Most people in Australia need sun protection when the UV Index reaches 3 and above. The UV Index is an international standard measurement of the strength of UV radiation from the sun at a particular place on a particular day. UV levels are lower in the early morning as the sun comes up, gradually increasing to a peak around the middle of the day when the sun is at its highest, and then decreasing slowly as the sun gets lower in the sky.
In northern parts of Australia (like Brisbane and Darwin), UV levels are above 3 all year round and reach extreme levels of 14+ in summer, so sun protection is needed daily.
In southern parts of the country, there are times of the year when sun protection is not necessary. For example, in Adelaide, the average daily UV levels remain below 3 in June and July, so sun protection is not required unless you are outside for extended periods or near highly reflective surfaces like water.
You can access the free SunSmart app to find out the daily sun protection times for your location.
Who is at risk of vitamin D deficiency?
There are groups within the population that are at higher risk of vitamin D deficiency including:
- people with naturally very dark skin—the melanin in dark skin affects UV penetration so you need more UV exposure to make vitamin D
- people with little or no sun exposure (e.g. older adults who are in residential care or housebound; those who wear concealing clothing for religious or cultural purposes; those who deliberately avoid sun exposure for cosmetic or health reasons; those who are hospitalised for a long time; those with a disability or chronic disease; and night-shift and indoor workers, such as office or factory workers who have limited incidental UV exposure throughout the day)
- breast fed babies who fall into the risk categories above or have mothers with low vitamin D—breast milk contains little vitamin D and infants depend on maternal stores initially. (Formula milk is fortified with vitamin D)
- people with health conditions (obesity, end stage liver disease, renal disease and fat malabsorption syndromes such as cystic fibrosis, coeliac disease, inflammatory bowel disease) or medications affecting vitamin D metabolism.
If you’re concerned about your vitamin D status , consult your GP. Vitamin D levels can be checked with a blood test, and your GP can advise on options, such as supplementation, depending on your individual circumstances.