Eating too much grapefruit too often may drastically increase
the risk of breast cancer, according to a new epidemiologic study conducted by
the
University of
Southern California and
published in the British Journal of Cancer advance online publication 10 July
2007.
Evidence revealed early through in vitro and in vivo studies
suggests that grapefruit inhibits CYP3A4, which is involved in the metabolism
of estrogen and increases plasma estrogen concentration, increasing risk of
breast cancer.
In the
Hawaii
-Los Angeles Multiethnic
Cohort
, Dr. K. R. Monroe from Department of Preventive
Medicine at the
University
of
Southern California
and colleagues conducted an epidemiologic study to see if there is an
association between consumption of grapefruit and breast cancer risk.
Among
50,000 postmenopausal women in five ethnic groups, 1657 breast
cancer cases were available for analysis. About 50 percent of the study
participants consumed grapefruit while 7 percent ate more than one quarter
grapefruit a day.
The researchers found that those who the highest amounts of
grapefruit, one quarter grapefruit a day were 30 percent more likely to develop
breast cancer compared to those who did not consume any.
Monroe and colleagues also found “
An increased risk of similar magnitude was
seen in users of oestrogen therapy, users of oestrogen+progestin therapy, and
among never users of hormone therapy.”
They conclude “
Grapefruit intake may increase the risk of breast cancer among
postmenopausal women.”
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