New Zealand's food safety watchdog wants to ban the sale of raw apricot kernels, which are advertised as an alternative treatment for cancer.
Food Standards Australia-New Zealand says the kernels contain dangerous, potentially fatal levels of cyanide.
Between 2003 and 2013, 20 people who had eaten large amounts called the National Poisons Centre complaining of stomach pain, palpitations and confusion.
Deaths in Gaza and Turkey have also been linked to excessive consumption of the kernels.
Food Standards manager of product safety standards, Leigh Henderson, said people did not understand the risks when eating the kernels.
"There's a problem in lack of awareness of the potential risk from those. And despite some labelling that indicates that levels should be restricted, people have eaten more than that," she said.
A website selling the product in New Zealand claimed the kernels contained anti-cancer properties, and were less toxic than chemotherapy.
But oncologist Chris Atkinson said there was no evidence to support the assertions.
"The compound that is thought to come from apricot kernels is laetrile. Some people have used laetrile for a 25-30 year period. If there had been strong evidence that that was a helpful thing to do, we could know that by now," he said.
He said alternative treatments like this often do more harm than good.
"There may be a build-up of other compounds that could cause problems, a bit like what's being hinted at in this situation," he said.
"The other thing is, you're putting faith in a particular remedy, and perhaps more faith would be better based around trying to cope with the enormity of the cancer."
Cancer Society chief executive Claire Austin said patients needed to trust that their doctors were doing everything they could to fight the disease.
"We understand that people diagnosed with cancer feel vulnerable and they look at a range of treatment options.
"But we advise people with cancer to have open and frank discussions with their doctor because some alternative medicines can impact on standard treatment or could actually risk causing greater harm," she said.
Food Standards Australia New Zealand is calling for submissions on the proposal to ban the sale of apricot kernels. Submissions close on 26 February.