Cancer specialists are rethinking their advice to cover up in the sun amid growing concern that staying in the shade may instead be causing harm.
Australia is revising its draconian warnings about the risks of sun exposure because of fears about vitamin D deficiency, which increases the risk of a range of diseases from cancer to osteoporosis, in what public health doctors are calling a "revolution".
The Cancer Council of Australia said this month: "A balance is required between avoiding an increase in the risk of skin cancer and achieving enough ultraviolet radiation exposure to achieve adequate vitamin D levels."
A survey in Geelong in Victoria cited in the Cancer Council's statement found that 43 per cent of women suffered mild vitamin D deficiency and 11 per cent had moderately severe deficiency during winter.
Geelong gets an average 2007 hours of sunshine a year.
Bruce Armstrong, professor of public health at Sydney University, said: "It is a revolution. I have worked in public health and been preaching sun avoidance for 25 years. But what this statement says is that there are two sides to the story."
Vitamin D is made by the action of the sun on the skin and can be stored by the body for up to 60 days. A shortage causes rickets in children, leaving their legs deformed.
New research has shown it is also linked to multiple sclerosis, diabetes and cancers including those of the colon, breast, ovary and prostate.
Some dermatologists are now starting to challenge the orthodox view that there is "no such thing as a safe tan", arguing instead that the real risk is from sunburn, especially before the age of 20.
Neil Walker, chairman of the UK Skin Cancer Prevention Working Party, has described warnings to avoid the sun entirely as "draconian and unnecessary".
His view was backed by Professor Brian Wharton, chairman of the British Nutrition Foundation, who said: "We do need some sensible use of the sun and we have been swinging too strongly against it."
Sara Hiom, head of health information at Cancer Research UK, said said concern about vitamin D deficiency was growing and an international conference hosted by the World Health Organisation was planned.
New Zealand is not changing its message about sun safety, despite the rethink over vitamin D deficiency in Australia.
Auckland Cancer Society health promotions manager Wendy Fulton said that every year 200 New Zealanders died from melanoma and although vitamin D was an important issue, most people got enough by walking to the letterbox or bus stop.
"The core message around Sun Smart still applies. We don't want people going out between 11am and 4pm in summer and exposing themselves to so much sun they get sunburned, especially children and young people."