The ingredient which makes jalapeno peppers hot also makes prostate cancer cells commit suicide, a study suggests.
Tests showed that capsaicin triggered 80% of the cells to start the process leading to cell death.
The US research in the journal Cancer Research also found tumours treated with capsaicin were smaller.
UK prostate experts say capsaicin could be the basis of a future drug but warned eating too many hot peppers has been linked to stomach cancer.
In the study, researchers from Cedars-Sinai Medical Center studied mice who had been genetically modified to have human prostate cancer cells.
They were given a dose of pepper extract equivalent to a man of 200 pounds (90.7kg) taking 400 milligrams of capsaicin three times a week.
That would be the same as having between three and eight fresh habanero peppers – the highest rated peppers for capsaicin content.
Normal cells go through a constant process where millions die every second – a process called apoptosis – while millions more are made, to keep the numbers the same.
But cancer cells avoid that process and “dodge” apoptosis by mutating or deregulating the genes that participate in programmed cell suicide.
Capsaicin was seen to increase the amount of certain proteins involved in the apoptosis process.
Capsaicin also reduced the amount of prostate-specific antigen (PSA), a protein whch is often produced in high quantities by prostate tumours.
Dr Soren Lehmann, who led the study, said: “Capsaicin had a profound anti-proliferative effect on human prostate cancer cells in culture.
“It also dramatically slowed the development of prostate tumours.”
Chris Hiley, head of policy and research at The Prostate Cancer Charity, said: “This is interesting laboratory-based work on cells but we don’t yet know how, if at all, it might help men with prostate cancer.
“Eventually, it may be possible to extract the capsaicin and make it available as a drug treatment.
“In the meantime we caution men with prostate cancer in the UK against upping their weekly intake of the hottest known chillies – high intake of hot chillies has been linked with stomach cancers in the populations of India and Mexico.
“For now, if men with prostate cancer want to improve their diet they should avoid fatty foods, eat less red and processed meat, increase their fish intake and enjoy a wide and plentiful range of fruit and vegetables every day.”