Short-term fasting may help boost treatment of cancer
Going without food for short periods may combat cancer and boost the effectiveness of treatments, an early animal study suggests.
Fasting on its own slowed the growth and spread of tumours in mice, scientists found.
When it was combined with chemotherapy, some serious cancers were cured.
Researchers are already looking at the effects of fasting on human patients.
Results from a Phase I safety study looking at breast, urinary tract and ovarian cancers will be presented at a meeting in the US this summer.
But only a clinical trial lasting several years will show if human cancer patients really can benefit from fasting, say the scientists.
They also warn that fasting could be dangerous for patients who have already lost a lot of weight or are affected by other risk factors, such as diabetes.
The research showed that tumour cells do not respond to the stress of fasting the same way as normal cells.
Instead of entering a dormant state similar to hibernation, they try to keep growing and dividing. In the end the cells destroy themselves.
"The cell is, in fact, committing cellular suicide," said lead scientist Professor Valter Longo, from the University of Southern California in the US.
"What we're seeing is that the cancer cell tries to compensate for the lack of all these things missing in the blood after fasting. It may be trying to replace them, but it can't."
The study is reported in the latest edition of the journal 'Science Translational Medicine'.
Mice with five out of eight different types of cancer responded to fasting alone, the researchers found.
Fasting without chemotherapy slowed the growth of breast cancer, melanoma skin cancer, glioma brain cancer and neuroblastoma.
In every case, combining fasting with chemotherapy made the cancer treatment more effective.
Multiple cycles of fasting combined with chemotherapy cured 20pc of mice with a highly aggressive type of children's cancer that had spread around the body.
Mice with a more limited spread of the same cancer were cured in 40pc of cases.
None of these mice survived if they were treated with chemotherapy alone, said the scientists.
Fasting also extended the survival of mice with a human ovarian cancer.
Results of the Phase I clinical trial will be presented at the annual meeting of the American Society of Cancer Oncologists (Asco) in Chicago in June.
Mr Longo pointed out that the study only tested whether patients could tolerate short fasts of two days before and one day after chemotherapy treatment.
"We don't know whether in humans it's effective," he said.
"It should be off-limits to patients, but a patient should be able to go to their oncologist and say, 'what about fasting with chemotherapy?' or without if chemotherapy was not recommended or considered."
Previous research led by Mr Longo showed that fasting protected normal cells from the effects of chemotherapy.
However, it did not look at cancer cells.
Fasting may be one way to make tumour cells weaker and more vulnerable, said Mr Longo.
He added: "A way to beat cancer cells may not be to try to find drugs that kill them specifically but to confuse them by generating extreme environments, such as fasting, that only normal cells can quickly respond to."