Vegetables tied to lower breast cancer risk

Cruciferous vegetables may help lower the risk of developing breast cancer, particularly for women who carry a particular gene variant linked to the disease, a new study suggests.

Researchers found that among more than 6,000 Chinese women, those with the highest intake of Chinese cabbage and white turnips had a somewhat lower risk of postmenopausal breast cancer than those with the lowest intake.

The findings, reported in the American Journal of Clinical Nutrition, add to evidence that compounds in cruciferous vegetables may help fight cancer.

Chinese cabbage and white turnips are two cruciferous vegetables common in the Chinese diet; in Western diets, the most common cruciferous vegetables include broccoli, cauliflower and kale. The vegetables contain certain compounds that the body converts into substances called isothiocyanates, which are thought to have anti-cancer effects.

In the current study, high consumption of Chinese cabbage and white turnips was linked to a moderately lower breast cancer risk. But the apparent benefit was stronger among women who carried two copies of a particular variant of a gene called GSTP1.

Among these women, those with the highest intake of any cruciferous vegetables had about half the risk of breast cancer as those who ate the fewest, according to the researchers, led by Dr. Sang-Ah Lee of Vanderbilt University in Nashville.

GSTP1 is an enzyme that helps detoxify the body of potentially cancer-causing substances. Some studies have suggested that having a particular form of the gene - the Val variant - may raise a woman's risk of breast cancer.

The current study found that women who carried two copies of the Val variant did, in fact, have a higher risk of developing breast cancer before menopause than women who had other variants in the GSTP1 gene.

But the excess risk was cut substantially in those who ate the most cruciferous vegetables.

"We cautiously interpreted this as diet being a factor that may reduce the impact of genetic susceptibility in overall breast cancer risk," Dr. Jay Fowke, one of the researchers on the work, said in a statement.

It's possible, according to Fowke and his colleagues, that people who carry two Val variants of the GSTP1 gene excrete the beneficial isothiocyanates more quickly, and eating more cruciferous vegetables helps counter this.

More research, they conclude, is needed to better understand how cruciferous vegetables might modify breast cancer risk.

SOURCE: American Journal of Clinical Nutrition, March 2008.