Why vitamin D deficiency matters and how to avoid it

Our sunburnt country has one of the highest incidence of skin cancer in the world, with two in three Australians diagnosed by the age of 70. But many of us also have the opposite problem: not enough sun. As a result, over 30 per cent of Australian adults have a mild, moderate or severe vitamin D deficiency.

Cool climates are a big contributor to the problem. In the southern states, vitamin D deficiency is more pronounced in winter when UV levels are low, explains Dr Paige van der Pligt, a senior lecturer in nutrition and dietetics at Deakin’s School of Exercise and Nutrition Sciences. ‘There is well-established seasonal variation and impact on vitamin D levels, and in winter it’s a lot harder to get to the levels we need for good health,’ she says.

Skin tone and year-round indoor lifestyles can compound the effects – not to mention snap lockdowns where we’re largely housebound.

Thankfully, it’s possible to give your vitamin D levels a boost in the cooler months without increasing your skin cancer risk.

How vitamin D levels affect your health

Vitamin D is a hormone that our bodies need to absorb calcium from the intestine to support healthy bones. It also supports growth and maintenance of the skeleton and regulates calcium levels in the blood. ‘The main role is to do with bone growth and bone development,’ Dr van der Pligt says.

Research shows vitamin D also plays a role in maintaining your immune system, nervous system and brain function, cognitive development, muscle function and reproductive health.

Vitamin D deficiency can lead to osteoporosis, bone and joint pain, and increase the risk of falls and fractures as you get older. Dr van der Pligt says emerging evidence suggests a lack of vitamin D may play a role in a range of health conditions, including type 2 diabetes, mental health issues, certain inflammatory conditions, obesity and heart disease.

If you have a vitamin D deficiency, symptoms might include fatigue, bone pain, muscle weakness or mood changes. You may also have no obvious symptoms.

Examining your risk of low vitamin D

Our best source of vitamin D is UVB radiation from the sun. Foods like eggs, fatty fish such as salmon and sardines, and fortified milk and margarine also contain vitamin D, but vitamin D synthesised from the sun is the more active form. ‘About 80% of our vitamin D comes from sunlight exposure and a small amount comes from the diet,’ Dr van der Pligt says.

The amount of sun exposure you need to make vitamin D depends on three main factors: your skin type, your lifestyle and the UV level. ‘Darker skin pigmentation can block UV from penetrating the skin, and people from Asian and African backgrounds have been shown to be at higher risk of vitamin D deficiency,’ Dr van der Pligt says. ‘The risk is also higher among people who wear covered clothing and spend a lot of time indoors.’

In winter, when UV levels are less intense, we need to spend more time in the sun to maintain adequate vitamin D levels. In Victoria, experts recommend two to three hours of sunlight exposure to the face, arms and hands each week – compared to just a few minutes a day in summer.

Preventing vitamin D deficiency

Taking a break from study or work and going for a walk outside in the middle of the day is one of the easiest ways to keep your vitamin D levels up during winter. ‘Make sure you’re spending a decent amount of time outside to obtain enough sunlight and UV exposure,’ Dr van der Pligt says. ‘We tend to cover up more in winter, but if there’s some sunshine around it’s beneficial to roll up your sleeves.’

Because the UV Index typically hovers below 3 during chilly Victorian winters, the Cancer Council says sun protection isn’t required unless you work outdoors all year round.

The same goes for vitamin D supplements. ‘The average person doesn’t need vitamin D supplements because it’s not difficult to obtain enough vitamin D from the sun, even in winter,’ Dr van der Pligt says. ‘Supplements should be used for people who are diagnosed with vitamin D deficiency because an excess of vitamin D can lead to significant problems.’