'Jury out' on multi-vitamins and cancer

  The "jury is still out" on whether multi-vitamin supplements have any impact - positive or negative - on a person's risk of developing cancer, an expert says.
A major Swedish study has linked multi-vitamin use to a heightened risk of breast cancer but Dr Helen Zorbas said it must be viewed alongside many other research papers which showed no such risk.
"Overall, one would have to say the evidence is inconclusive," said Dr Zorbas, who is executive director of National Breast and Ovarian Cancer Centre and holds a staff specialist position at Sydney's Royal Prince Alfred Hospital.
"There are a number of studies looking at different vitamins but when you look at them overall they are inconsistent ... and that applies to vitamins A, C, D and folate.
"The use of multi-vitamins in the belief that they prevent chronic diseases like cancer and cardiovascular disease aren't proven.
"If you are taking them in a preventative way, it's important to keep in mind that the jury is still out on their benefits and risks."
The study, conducted by Sweden's Karolinska Institute and published in the American Journal of Clinical Nutrition, tracked 35,000 women over 10 years and those who took a daily multi-vitamin pill were found to have a 19 per cent increased risk of breast tumour.
The result was concerning, the researchers said, as many women used multi-vitamins in the belief they were protective against cancer.
Dr Zorbas said she did not think the study, at this point, represented "strong evidence" against taking multi-vitamins though "the best source of vitamins is through eating fresh fruit and vegetables, so that you get them from the natural source".
Women who took vitamin supplements to treat a deficiency in consultation with their GP should continue to do so, she said.
And for those women worried about their breast cancer risk, Dr Zorbas said there were a range of healthy lifestyle changes that were supported by research.
"We do have fairly strong evidence in relation to increased risk related to alcohol consumption, to obesity, particularly in women post-menopausal, and good evidence around decreased risk in women who exercise regularly," she said.
"These are things we do know in relation to breast cancer risk, which are modifiable factors that women can act on