A product that rugby legend Sir Colin Meads says has extended his life expectancy has not been approved by medical experts.
Meads, 80, who has pancreatic cancer, attributes "Taranaki water" to his improvement.
But Cancer Society medical director Dr Chris Jackson told Fairfax that products and supplements needed to be approved by Medsafe which reviewed quality, safety and efficacy from clinical trials.
"Treatments and supplements that work well for one individual with one type of cancer may be unhelpful or even harmful for others."
He said anyone considering alternative treatment options should seek advice from their oncologist or medical practitioner.