Cancer Research UK cautious over grapefruit breast cancer link

In collaboration with the Press Association

Cancer Research UK has played down reports of a link between eating grapefruit and an increased risk of breast cancer in postmenopausal women.

A study by scientists at the Universities of Southern California in Los Angeles and Hawaii in Honolulu reported that eating as little as a quarter of a grapefruit a day may increase the risk of breast cancer in older women by 30 per cent.

But a Cancer Research UK spokesperson pointed out that it was the first study to find such a link.

Researchers analysed data from around 46,000 women taking part in the Hawaii-Los Angeles Multiethnic Study, 1,657 of whom had been diagnosed with breast cancer.

Study participants were asked how much grapefruit they had consumed daily over the previous 12 months.

The researchers found that grapefruit consumption was "significantly associated" with an increased risk of breast cancer, and propose that that the link could be due to the fruit increasing blood levels of the hormone oestrogen, which is known to be associated with breast cancer risk.

Previous research has revealed that a molecule called cytochrome P450 3A4 (CYP3A4) helps to break down oestrogen.

Grapefruit is thought to inhibit this molecule, and the team suggests that this could, in theory, raise levels of oestrogen in the blood.

However, Liz Baker, science information officer at Cancer Research UK, said: "Although the chemicals in grapefruit are known to interfere with the action of several drugs, this is the first and only study to show a link between grapefruit and breast cancer risk, and the researchers themselves say that the results need to be confirmed in follow-up studies.

"What we do know is that eating a good mix of at least five fruit and vegetables a day can reduce the risk of many diseases, including some cancers."