A recent e-mail forwarded around the world has some people concerned about grapefruit. The messages refer to a 2007 study in The British Journal of Cancer that found an increased risk of breast cancer among postmenopausal women who ate large amounts of grapefruit. In the group of women, more than 46,000 over all, those who ate about a half a grapefruit every other day had a 30 percent higher risk of breast cancer than those who ate none, even after other risk factors were taken into account. Grapefruit contains several compounds that inhibit the CYP 3A4 enzyme, thus increasing the level of substances that are normally metabolized by 3A4, including estrogen.
But a more recent report published in the same journal reached a far different conclusion. That analysis used data from the Nurses’ Health Study, which followed more than 77,000 women 30 to 55 over many years. The scientists looked at intake of both grapefruit and grapefruit juice and found no rise in breast cancer risk .
Experts at the American Cancer Society said that there was insufficient evidence to change existing recommendations, but that women with concerns could cut back on grapefruit.

ANAHAD O’CONNOR