She said it was illegal for complementary medicines in Australia to make claims about treating cancer and the Cancer Council's concerns must be related to products bought overseas and online.
More than one in two cancer patients now use alternative therapies which have exploded into a $4 billion a year industry.
Cancer Council chief Professor Ian Olver said it was critical patients who wanted to use these therapies discuss them with their doctor and were aware they could interact with their conventional cancer treatments.
There was good evidence that Vitamin C interacted with the prescription medicine methatrexate used in cancer and acidified the urine and slowed down the excretion of the drug, he said.
Read more: http://www.news.com.au/lifestyle/health-fitness/cancer-councils-danger-warning-on-complementary-medicine-therapies/story-fneuzlbd-1226591052296#ixzz2Mlsj1L1U