Cabbage chemical may bar breast cancer.

Cabbage chemical may bar breast cancer

In publicly declaring his distaste for broccoli, President Bush found widespread bipartisan support. But if preliminary research results are confirmed, broccoli, cabbage, bok choy and other much-maligned cruciferous vegetables may eventually get a boost in the polls.

Two scientists report discovering that vegetables from the Brassica genus, whether raw or lightly cooked, contain a chemical that spurs the body to convert more of the hormone estrogen into an inactive form. Because estrogen can fuel the development of certain breast tumors, the crucifer compound might lower a woman's breast cancer risk, the researchers suggest.

Past studies have linked Brassica-rich diets to a lower risk of other cancers. But the new work is the first to show a connection between a specific crucifer compound and enhanced estrogen metabolism in healthy people, say Jon J. Michnovicz and H. Leon Bradlow of the Institute for Hormone Research in New York City. They add that it might help explain why Asian women, who eat lots of crucifers, have a much lower breast cancer rate than Western women.

"This may be a link between diet and protection against breast cancer," says Christopher Longcope of the University of Massachusetts Medical School in Worcester. He cautions, however, that future work must demonstrate that the compound can indeed help stave off breast cancer in women.

Michnovicz and Bradlow focused on various nitrogen-containing compounds called indoles, which other researchers had pegged as anticancer agents (SN: 11/25/89, p. 351). In female rats, they discovered that a specific indole, known as indole-3-carbinol, significantly boosted the rate at which an enzyme converted a form of estrogen to 2-hydroxyestrone, an inactive version that doesn't trigger mammary tumor growth.

The researchers went on to test the compound in seven healthy men. (Men produce estrogen at low levels that do not fluctuate as much as women's, simplifying interpretation of laboratory results.) Each man received a daily dose of 500 milligrams of indole-3-carbinol, equivalent to the amount contained in half a head of cabbage. After a week on the indole extract, their production of 2-hydroxyestrone increased by about 50 percent as measured in urine samples. Michnovicz and Bradlow describe the findings in the June 6 JOURNAL OF THE NATIONAL CANCER INSTITUTE.

In a recent, unpublished study of five healthy women who got similar treatment, they obtained virtually identical results, Michnovicz told SCIENCE NEWS.

The team hypothesizes the 2-hydroxyestrone may block estrogen receptors in breast cells, thus helping to prevent estrogen-fueled cancers. In addition, Longcope suggests, increased 2-hydroxyestrone production may mean the body forms less 16-alpha-hydroxyestrone, a potentially carcinogenic form of estrogen.

New, unpublished results with female mice already hint at indole-3-carbinol's power to prevent breast cancer. The New York researchers gave the compound to mice infected with a virus that leads to mammary tumors. After eight months, only 25 percent of the mice developed breast tumors, compared with 80 to 90 percent of virally infected control mice, Michnovicz told SCIENCE NEWS.

It will take years, he says, to establish the chemical's cancer-preventing potential in women -- and even then, some finicky eaters will continue to turn up their noses at the first whiff of a crucifer. Michnovicz suggests his research might overcome that hurdle with an indole-3-carbinol dietary supplement that would allow women to gain protection without forcing down the hated vegetables. He notes, however, that real crucifers offer additional benefits such as vitamins A and E.