They believe that high levels of glucosinolates, compounds already demonstrated to have anti-cancer activity in the lab, are responsible for the association between cabbage and sauerkraut consumption, and a lower risk of breast cancer observed in Polish immigrants living in the US.
"The observed pattern of risk reduction indicates that the breakdown products of glucosinolates in cabbage may affect both the initiation phase of carcinogenesis -by decreasing the amount of DNA damage and cell mutation -and the promotion phase, by blocking the processes that inhibit programmed cell death and stimulate unregulated cell growth," said Dorothy Rybaczyk-Pathak from the University of New Mexico.
Pathak, along with colleagues from Michigan State University and the National Food and Nutrition Institute of Warsaw, Poland, evaluated the diet of Polish immigrants living in Chicago and surrounding Cook County, and the Detroit, Michigan, metropolitan area.
Women who ate at least three servings a week of raw- or short-cooked cabbage and sauerkraut had a significantly reduced breast cancer risk compared with those who only ate one serving per week, they said at the American Association for Cancer Research's Frontiers in Cancer Prevention Research meeting in Baltimore this week.
The study was triggered by Pathak's observation that the breast cancer risk of Polish women rose three-fold after they immigrated to the United States.
In Poland, where abundance of food is a recent phenomenon, women traditionally eat an average of 30 pounds of cabbage and sauerkraut per year, as opposed to just 10 pounds per year among American women. Polish women also traditionally eat more raw cabbage and sauerkraut in salads or as a side dish.
Pathak found the lowest rate of breast cancer among women who consumed high amounts of raw- or short-cooked cabbage during adolescence. Yet high consumption during adulthood provided a significant protective effect for women who had eaten smaller quantities of this vegetable during adolescence.
Cabbage cooked a long time had no bearing on breast cancer risk.
A number of studies have linked consumption of cruciferous vegetables to lower risk of cancer, and more recently, laboratory research has supported this link. For example, a recent Italian study found that juice from different cauliflower varieties suppressed cell proliferation in a dose-dependent manner and caused significant cell death at the higher juice concentrations.
Researchers have also recently reported that glucosinolates could help reduce the risk of lung cancer for some people with a particular genetic make-up.
Other cruciferous vegetables that contain glucosinolates include broccoli, Brussels sprouts and kale. Yet research has shown that the compounds are destroyed by storage and processing. Chopping, on the other hand, helps to increase the availability of compounds.