US scientists have carried out a series of laboratory tests suggesting that natural compounds in pomegranates may prevent the growth of breast cancer cells.
But experts cautioned that the results didn't mean that eating the fruit could prevent or treat the disease as the compounds were hard for the body to absorb, and the study used relatively large amounts.
Pomegranates contain a group of compounds called ellagitannins, the subject of the latest research at City of Hope, a cancer centre in California.
Dr Shiuan Chen, director of the Division of Tumour Cell Biology, and Dr Lynn Adams, a research fellow at the centre's Beckman Research Institute, set out to determine whether chemicals in pomegranates could block the action of an enzyme called aromatase.
Aromatase plays a key role in driving the growth of some forms of breast cancer by helping the body produce the female sex hormone oestrogen. Breast cancer drugs like anastrozole are designed to block its action.
The researchers screened ten ellagitannin-like compounds and found that one in particular, Urolithin B, significantly inhibited breast cancer cell growth in the laboratory.
Dr Chen admitted that the team was "surprised" by the findings, which are published in the journal Cancer Prevention Research.
"We previously found other fruits, such as grapes, to be capable of the inhibition of aromatase. But phytochemicals in pomegranates and in grapes are different," the researcher explained.
Dr Gary Stoner, a professor in the department of internal medicine at Ohio State University who was not involved in the research, noted that further studies will be needed before scientists know whether Urolithin B is effective against hormone-dependent breast cancer.
"This is an in-vitro study in which relatively high levels of ellagitannin compounds were required to demonstrate an anti-proliferative effect on cultured breast cancer cells," he explained.
"It's not clear that these levels could be achieved in animals or in humans because the ellagitannins are not well absorbed into blood when provided in the diet."
Dr Laura Bell, science information officer at Cancer Research UK, agreed, saying: "It's too big a leap to conclude from this early-stage research that eating pomegranates could help prevent hormone-dependent breast cancer as the study was done using large amounts of purified chemicals on cells grown in the lab.
"In terms of cancer prevention, most foods contain many natural chemicals and we need to understand the combined effect of these when processed in the body to guess what influence, if any, a specific food may have on your chance of developing cancer."
Dr Bell continued: "We know from large scientific studies that by eating a healthy balanced diet high in fibre, fruit and vegetables and low in red and processed meat, saturated fat and salt, you can help to reduce your risk of several different types of cancer."
Study shows cannabis as a genotoxic substance with cancer risks