An accidental discovery found that breast milk contains a substance nicknamed Hamlet that kills off tumour cells.
Researchers said that it does not have the same side effects as chemotherapy because it does not target health cells in the body.
Professor Catharina Svanborg, from Lund University, Sweden, told the Mail on Sunday: ‘There’s something magical about Hamlet’s ability to target tumour cells and killthem.’
Bladder cancer patients have already undergone tests and returned promising results. Researchers are now also looking at whether it can help in the fight against bowel and cervical cancers.
Prof Svanborg added: ‘We were looking for novel antimicrobial agents, and new breast milk is a very good source of these. During one experiment we needed human cells and bacteria to be present, and we chose human tumour cells for practical reasons.
‘To our amazement, when we added this compound of milk, the tumour cells died. It was a totally serendipitous discovery.’
They believe that a reaction takes place with breast milk when it hits the gut.
It produces a protein called alpha-lactalbumin which targets cancer cells.
Hamlet helps to get rid of the cancerous cells in their urine within just a matter of days and a trial is hoped to start in the future.
Last week we reported on a father who had started drinking his own daughter’s breast milk to try and help beat cancer.
Fred Whitelaw, 64, was diagnosed with bowel cancer in 2015 and it returned last April.
His daughter, Jill Turner, 30, started expressing milk for him after reading research that breast milk could help kill off cancerous cells.
She gave birth in October to Llewyn and expresses more than she needs so she is able to give some of her excess milk to her father.
Fred said he was hesitant at first, but has reached the point where he believes he’s got nothing to lose.
Jill, from Rugby, Warwickshire, said: ‘I was devastated when I found out about my dad’s diagnosis. I wanted to help him in any way I could and that’s when I started to give him my breast milk.
‘I was researching online when I came across an article for alternative uses for breast milk.
‘Since then my husband, Kyle, 30, has used it on his eczema and we have also used it on Llewyn’s conjunctivitis.
‘But when I mentioned to my family that it has links with cancer they thought I was joking. Never did I think that my dad would agree to drink it.
‘But he too realised he had nothing to lose and thought, “why not try it”.’