All Clear For Grapefruit

"Good news for grapefruit lovers: Two follow-up studies failed
to confirm a 2007 study reporting that grapefruit eaters have a
higher risk of breast cancer.
In 2007, the Hawaii-Los Angeles Multiethnic Cohort Study-
which tracked more than 46,000 postmenopausal women from five
racial or ethnic groups for six to nine years- found a 30 percent
higher risk of breast cancer in those who averaged about a quarter
of a grapefruit a day than in those who ate none. The link seemed
plausible because of evidence that grapefruit might increase blood
estrogen levels by inhibiting an intestinal enzyme that metabolizes
estrogens.
However, the Nurses' Health Study, which monitored more than
77,000 women for 18 years, found no link between breast cancer and
grapefruit when researchers looked at all women. What's more, among
women who had never taken postmenopausal hormones, those who ate an
average of at least a quarter of a grapefruit a day had a 22 percent
lower risk of breast cancer.
And the European Prospective Investigation into Cancer and Nutrition
(EPIC), which tracked nearly 115,000 women for 10 years, also found
no overall link between grapefruit and breast cancer. So, enjoy your
grapefruit, unless it interferes with any medications you're taking."

-Nutrition Action Healthletter, March 2011