After years of health warnings about sun exposure, some doctors now believe ultraviolet rays can help reduce the chance of getting some types of cancers by close to 50 per cent.
Professor Rachel Neale is recruiting 25,000 Australians to test the hypothesis that the vitamin D boost resulting from exposure to the sun can reduce the chance of ovarian, oesophageal and pancreatic cancers.
Professor Neale's previous studies show those who had lived in places with higher levels of UV rays had a 30 to 40 per cent lower risk of pancreatic cancer than those who had lived in places with lower ambient UV rays.
The studies, involving hundreds of participants, linked high UV exposure to a 30 per cent reduced risk of ovarian cancer and a 40 per cent reduced risk of oesophageal cancers.
Sun exposure was particularly helpful to those with the more sun-sensitive fair skin, leading to a 47 per cent reduced risk of pancreatic cancer, compared with those with a tan.
Professor Neale, from the QIMR Berghoffer Medical Research Institute in Brisbane, said it was not known whether it was possible to achieve the full cancer-fighting advantage of Vitamin D by taking it in a pill form, or whether the apparent health benefits relied on the sun.
"We certainly are not hand on heart saying this is definitely true, in these types of epidemiological studies we are always very cautious about saying something is causal, but we do see an association between UV exposure and some cancers," she said.
"We have tried to adjust for other factors that might influence their risk of cancer (in the studies) and the association remained."
Australia is regarded as having a high UV index, reaching 12 to 14 in summer compared with 8 in Britain.
While the UV index across the country is similar in summer, WA has one of the higher UV indexes in winter, hitting three on the index.
Professor Neale's trial used NASA's total ozone mapping spectrometer, which rates UV by postcode.
Each participant will be assigned a lifetime UV score, based on previous places of residence across their lifetime.
But despite the apparent benefits, Professor Neale said it was important not to rush into the sun without adequate skin protection because too much exposure was still linked to skin cancer.
'We have tried to adjust for other factors … and the association remained.'" *Professor Rachel Neale *