By Ingrid Hipkiss
An Australian study has found living further south could almost double a woman's chance of developing breast cancer.
The higher risk zone includes Perth, Adelaide, most of New South Wales and all of New Zealand.
Researchers at the Westmead Institute in Sydney think the increased breast cancer risk is all down to sunlight and vitamin D. The further south you live, the less potential there is for safe sunlight exposure and therefore less opportunity for the body to produce vitamin D.
Auckland Cancer Centre oncologist Anna Bashford says the evidence is not yet conclusive.
“Vitamin D is a very hot topic in breast cancer at the moment and there's certainly a lot of scientific evidence to say that it may be an important factor, but studies in actual women have been conflicting.”
The new study found that Australian women living south of latitude 30 were almost twice as likely to develop breast cancer as those living further north. New Zealand is entirely in the high-risk area.
But the New Zealand Cancer Society is cautious is about the claim.
“People can actually end up with skin cancers because they've decided to err on the side of, ‘I’d rather have more vitamin D than protect my skin,’ and in New Zealand with our high ultraviolet [levels], especially in summer, that's a very real risk,” deputy chief executive Dr Jan Pearson says.
But breast cancer researcher Euphemia Leung says the sunsmart message means many New Zealanders are vitamin D deficient.
“It is essential for your body, and I think if you have too low sunlight exposure it’s likely you will be deficient, and therefore sunlight exposure is good, but getting fried in the sun isn't.”
New Zealand figures don't suggest any link between latitude and the risk of breast cancer. The Waitemata region has the highest rate of breast cancer, while Nelson Marlborough has the lowest.
The experts agree more research is needed, and in Australia 600 women with early stage breast cancer are being recruited to test whether their vitamin D levels affect their tumour growth.
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