It’s not just about your bones falling apart. A raft of recent studies finds that a healthy dose of sunshine supports the immune system, and can reduce the risk of heart disease, obesity and diabetes, asthma, inflammatory bowel problems, even multiple sclerosis – as well as the loss of bone density associated with a drop in vitamin D levels.

Most people are aware of the latter association. As of five years ago, the Australian Health Survey showed one quarter (23.5 per cent) of Australians are vitamin D deficient – and we were spending about $94 million a year on supplements, with consumption peaking in the darker winter months.

This was in a study that explored the need for vitamin D supplement guidelines – and a side issue here is that it’s now thought the threshold for deficiency was set too high.

As one researcher told The New Daily, vitamin D supplements won’t substitute for many of the benefits of sunshine.    

Besides, as CHOICE noted in 2014, in response to the health survey, for most people, “sensible sun exposure is the easiest way to increase your vitamin D levels”.

At odds with this advice, Australians have come to regard sunshine as a ferocious killer to be studiously avoided: after all, skin cancer is the most common form of cancer in Australia.

Inevitably, children are especially subject to being hatted and swaddled and smothered in sun protection creams. And then later in life being prescribed vitamin D capsules to reverse deficiencies revealed in blood tests.

Meanwhile, among scientists, there’s long-standing enthusiasm that we turn our bodies back to the light. Or rather, that we dose ourselves on sunlight rather than pills. But how big should that dosage be?

A 2014 discussion paper from the Cellular Photoimmunology Group at the Sydney Medical School noted: “Despite years of research attention into the biological effects of sunlight exposure, we are still far from being able to fully answer the question: How much sunlight is enough?”

Get kids outside

Professor Robyn Lucas is a medically trained epidemiologist and specialist public health physician at the Australian National University College of Health and Medicine.

This week Professor Lucas and colleagues published a study that found children who spend half an hour a day outside in the sun reduce their risk of inflammatory bowel disease (IBD).

More than 800,000 people live with the two life-long disorders that make up IBD – Crohn’s disease and ulcerative colitis.

“We found children who were outside and exposed to the sun for an extra half hour a day in total, had a lower risk of developing IBD by almost 20 per cent,” she said.

Children who receive more sunlight are less likely to develop inflammatory bowel disease, studies found. Photo: Getty

How does this happen?

As Professor Lucas explained to The New Daily, it was previously thought that a lack of sunshine led to a suppression of immunity.

It’s now understood sunshine enhances the immune system – notably the adaptive immune system which can turn against itself, in the form of auto-immune diseases such as IBD, Diabete-1, and multiple sclerosis. Sunlight works against that self-destructive potential.

She said everyone needs a bit of sun exposure every day, or at least most days of the week.

“But we are not talking about sunbaking or getting sunburnt,” she said.

What’s the right time to spend in the sun?

According to CHOICE, in order to maintain adequate vitamin D levels it’s recommended people with moderately fair skin get six to seven minutes of sun with arms and hands exposed outside the hours of 10am to 2pm (11am to 3pm daylight savings time) in the warmer months.

In winter, this translates to seven to 40 minutes at noon, depending on your location, with as much bare skin exposed as possible. People with dark skin may need three to six times as long.

The health benefits of sunlight are further improved when combined with exercise.