Eating grapefruit may increase the risk of breast cancer by up to a third.

Accordingto new research, eating as little as a quarter of a grapefruit a daymay increase the risk by 30 per cent in older women.

Breast cancer accounts for more than a quarter of all cancers inwomen. More than 40,000 cases are diagnosed and around 12,500 women diefrom the disease in the UK each year.

"This is the first report of a commonly consumed food that mayincrease the risk of breast cancer among postmenopausal women," say theresearchers. "Whole grapefruit intake was significantly associated withbreast cancer in the present study – generally, a 30 per cent increaseamong women who consume the equivalent of one quarter of a grapefruitor more per day."

It is thought the fruit increases blood levels of oestrogen, thehormone associated with breast cancer risk. The research, reported inthe British Journal of Cancer, is based on a study group of around46,000 women, including 1,657 with breast cancer.

The women sampled are among those taking part in the long running Hawaii-Los Angeles Multiethnic Study.

In the study, the women were asked how much grapefruit they hadconsumed daily during the previous year. Overall, whole grapefruit wasconsumed by 50 per cent of the women, with 7 per cent having an intakeof one quarter of a grapefruit or more a day.