August 15, 2007 – According to an American study, consuming a quarter of grapefruit or more per day could increase by 30% the risk of developing breast cancer in postmenopausal women. But we will have to wait for further research before condemning this fruit.
These results are from a cohort study conducted in California and Hawaii among 46,080 postmenopausal women.1.
The authors of the study initially sought to verify whether grapefruit – the fruit only and not its juice – contributes to the build-up of estrogen levels in the body, which is considered a risk factor for breast cancer.
Their conclusions are based on answers to a written questionnaire, filled with memory, aimed at knowing the foods consumed by the subjects during the previous months.
An enzyme called CYP3A4
In recent years, grapefruit juice has been known to have an inhibitory effect on an enzyme, cytochrome P450 3A4 (CYP3A4). Besides the fact that its name suggests a telephone code or a postal code, this enzyme contributes, in the body, to the elimination of a number of substances. When its action is inhibited, said substances therefore run the risk of accumulating in the body.
Previous studies have shown that grapefruit juice has the effect of increasing the levels in the body of 60% of prescription drugs. Estrogens are said to be one of those substances whose metabolism depends on CYP3A4. However, it is believed that breast cancer could be associated with an increase in blood estrogen levels.
According to pharmacist Jean-Yves Dionne, a specialist in natural health products, it is certainly too early to be alarmed. “The inhibitory effect of grapefruit on CYP3A4 is very real, but it would be clearly outrageous to conclude that this fruit has carcinogenic effects”, he argues.
The researchers agree that more studies will need to be done on grapefruit and its juice even though it is possible that this fruit increases the risk of developing breast cancer, they conclude.
Pierre Lefrançois – PasseportSanté.net
According to BBC and FoodNavigator-USA
1. Monroe KR, Murphy SP et al. Prospective study of grapefruit intake and risk of breast cancer in postmenopausal women: the Multiethnic Cohort Study. Br J Cancer. 2007 Jul 10.
