Date Published: 1 October 2005

Sun's rays may do us good, according to Australian cancer expert

Cancer epidemiologist Professor Bruce Armstrong has added to the debate about the risks and benefits of exposure to the sun by suggesting that a moderate amount of sunlight may protect people against a range of serious illnesses.

Professor Armstrong, head of the University's School of Public Health, said there was growing evidence that "safe levels" of sunlight could provide protection against multiple sclerosis, prostate cancer and non-Hodgkin lymphoma, and improve the chances of survival from prostate cancer and melanoma.

For some years, public health researchers have been guardedly promoting the benefits of sunlight for its vitamin D boost to calcium and bones, despite opposition led in particular by US dermatologists. But Professor Armstrong's paper to the World Congress on Melanoma in Vancouver has taken the debate to a new level.

Professor Armstrong said research indicated there might be an optimal level of sun exposure for everyone, where the net benefits were at their highest and exceeded the net harms. And contrary to the tide of current medical opinion, he said the benefits may not be entirely due to vitamin D.

" It's still early days, but we may have to start thinking about UV radiation in the same way we view alcohol: that in moderation, it may be good for you" he said.

However he pointed out that a safe level of exposure in the Australian summer could be measured in minutes rather than hours, and that conveying the idea of sunlight as beneficial presented a complex communication challenge.

Professor Armstrong, who has been researching melanoma for almost 30 years, was presented with a lifetime achievement award at the conference for his work on understanding the risk factors involved in skin cancers.

In his congress paper, he said it seemed likely that exposure to sunlight provided benefits beyond those of vitamin D supplements.

" There is no certainty that all known, much less yet to be known, beneficial effects of sun exposure are mediated through vitamin D production,"

he said. For example, a probable beneficial effect against multiple sclerosis could be due to an immune suppressant effect of sun exposure which was not necessarily dependent on vitamin D.

" It is increasingly likely that there is a safe level of sun exposure, below which the benefits outweigh the hazards. More importantly, perhaps there is an optimal level at which the net benefits of sun exposure are both positive and greatest. These concepts present challenges in public communication about sun exposure and sun protection."

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