FLOW-ON EFFECT: Malia Flasza sets up a machine for colonic irrigation. She believes it can work alongside cancer treatments.

Cancer patients are being warned by a medical expert that some complementary therapies are not only useless, but could be dangerous.

In a public lecture at Victoria University in Wellington last night, Professor Shaun Holt said there were no complementary natural therapies that could cure cancer.

Complementary therapies are non-conventional medical treatments – such as meditation, hypnosis or the prescription of substances such as ginger or capsicum – used alongside conventional treatment.

More than half of all cancer sufferers used complementary therapies, Prof Holt said. "A lot of people want to do whatever they can do to maximise their chances of getting good health."

Although he expected opposition from practitioners of complementary therapies, the academic said his findings were not his own opinions but were based on years of research into scientific evidence.

"There are a lot of practices out there that are not going to help. There are some that are going to harm."

He said many practitioners were genuine people but "misguided" if they believed they could cure cancer. Others were trying to extract money from people's suffering, though he did not believe that was common in New Zealand.

While some therapies could be useful in helping to reduce symptoms or could improve quality of life, others would not.

Chiropractors were good at helping people with bad backs, but would not help cancer; reiki was "chanting mumbo jumbo"; reflexology was "absolute nonsense"; and colonic irrigation was dangerous, he said.

The professor's assessment of colonic irrigation was disputed by practitioner Malia Flasza.

Mrs Flasza, 48, who worked as a nurse for more than 20 years before training to deliver colonic irrigation, and said that, although it was not scientifically proven, she "truly" believed in its effects.

She would use the treatment on cancer patients while working closely with an oncologist, she said.

She is in remission for non-Hodgkin's lymphoma and had used natural therapies towards the end of her chemotherapy course and then started using colonic irrigation. "There is room for the two to work side by side."

Mrs Flasza found the size of her tumours reduced and she also felt the benefits of the irrigation.

Wellington naturopath Jill Casey said she would recommend homoeopathy as a treatment for cancer patients as it was "fairly innocuous", although this was a treatment Prof Holt said would have no effects.

She said complementary therapies were unfairly judged by people who had not tried them, and it was important not to make sweeping statements about how they would affect individuals.

Prof Holt's "No1 recommendation" was yoga, which was particularly effective for breast cancer patients. Taking ginger was also highly recommended, and he said that, for patients experiencing nausea and vomiting, it was as effective as pharmaceutical drugs.

The Cancer Society's assistant divisional manager, Fiona Pearson, said there would be cancer sufferers undertaking harmful treatments "under the radar", as there were some treatments that could be counter-productive.

Many complementary therapies could help cancer sufferers, but she suggested discussing them with a doctor before treatment.

Wellington Hospital said its oncologists would not comment on complementary therapies in cancer treatments, because their effect on individuals varied.

SHAUN HOLT'S VERDICT

WHAT WORKS

Acupuncture: Can be used to relieve a number of symptoms that are commonly experienced by cancer patients.

Massage therapy: Can help reduce stress, anxiety, pain and other symptoms.

Aromatherapy: Can reduce anxiety, depression, tension, pain and nausea. There are no important safety issues, so aromatherapy is recommended as a pleasant and medically useful treatment.

Art therapy: An excellent option for people with cancer who are looking to reduce symptoms and help with the psychological trauma of a cancer diagnosis.

WHAT DOESN'T WORK

Colonic irrigation: Professor Holt says many people are at risk of adverse effects from this therapy, which he says is as ineffective and dangerous as it is ridiculous.

Cupping: Celebrities photographed with cupping marks have increased the demand for a procedure with no scientific plausibility or research evidence to support its use.

Ear candling: Associated dangers include external burns, obstruction of the ear canal with wax, and perforated eardrums resulting from hot wax dripping on them.

Psychic surgery: The practitioner's hands appear to magically penetrate the patient's body, after which they are removed holding organic matter claimed to be the tumour. Professor Holt says psychic surgeons are basically skilled magicians and the operation is actually an optical illusion using sleight of hand, animal tissue and clotted blood.