By Michael Day, Health Correspondent,

Adult cancer patients are taking breast milk in an attempt to to boost their immune systems and reduce the side effects of chemotherapy. A milk bank in California has quietly supplied 28 adult patients in the past four years with donated breast milk.

The Mothers' Milk Bank, one of six in the United States, distributes the milk mainly to premature and low-birth-weight babies but also gives it to adults with a doctor’s prescription.

Cancer specialists in Britain and America were sceptical about the treatment last night, saying that there was little or no hard evidence that it worked. Some of the patients - who drink several ounces of milk a day to ease the ravages of their drugs - said, however, that it had led to big improvements in their general health, and had a powerful anti-cancer effect.

One recipient, Howard Cohen, a computer consultant from Palo Alto, said that his twice-weekly "smoothies" made with breast milk and fruit had helped put his prostate cancer into remission and allowed him to avoid more invasive treatment, such as surgery.

Mr Cohen first took breast milk after he was diagnosed in 1999. His wife read an article about Swedish research on breast milk and cancer cells. A friend who was breast-feeding at the time gave him some of her milk, and Mr Cohen found that his levels of prostate-specific antigen, a warning sign for prostate cancer, dropped back to normal.

His urologist was sceptical but not opposed to Mr Cohen’s self-treatment so long as it had no adverse effects.

Mr Cohen has undergone regular blood tests and screenings in the past two-and-a-half years and there have been no signs of cancer, though his doctor has pointed out that some prostate cancers grow so slowly that it is possible that the breast milk made little or no difference.

He dismissed concerns that drinking breast milk could even be harmful. "You give this stuff to newborn babies,'' Mr Cohen said. "It can't be toxic.''

Breast milk’s benefits for babies are well-documented. Research shows that it helps fight infection, improves immune system function, increases intelligence and combats obesity in later life. Little research has, however, been carried out on the medicinal effects for adults.

In 1995 Swedish researchers, whose work caught Mr Cohen’s attention, isolated a protein in mothers' milk that seemed to kill cancer cells in a test tube and are still trying to develop a drug that takes advantage of that protein.

Many doctors remain sceptical about the value of breast milk for adults, however. They point out that many chemicals will kill cancer cells in a test tube without having a hope of becoming viable treatments.

Dr Michelle Melisko, a consultant oncologist at the University of California-San Francisco, said that mothers' milk was probably unlikely to harm her patients but she did have some concerns.

Some viruses could be passed through breast milk - a potentially serious threat to patients whose immune systems have been weakened by cancer treatments - and she had advised them against using it.

"I’d say the same thing I say to all my patients who want to do alternative things: I don't know how it’s tested,'' Dr Melisko said.

Dr Margit Hamosh, however, a biochemist and human breast milk specialist at Georgetown University, said that breast milk contained compounds "that might definitely help in people who have compromised immune systems."

David Kerr, the professor of clinical pharmacology and cancer therapeutics at Oxford University, said: "This is quite bizarre, completely anecdotal and probably complete bunkum.

"It probably won't do any harm but it’s unlikely to do any good either.

"People with cancer and their families of course want to leave no stone unturned when it come to looking for a cure, and who am I to stand in their way?

"I do warn, however, that there are many charlatans out there. And I think there are several rules to stick by: the product should not cost an arm and a leg; it shouldn't do undue harm, and it shouldn't interfere with the conventional treatments."