Answer : Cabbage, from which sauerkraut is made, is a cruciferous vegetable (like broccoli). The compounds that give cruciferous vegetables their sometimes-bitter taste and distinctive smell help protect the plants from insects and munching herbivores; when broken down in the human digestive system, these same compounds may help protect against cancer. Studies have shown that people who eat more cruciferous vegetables, including cabbage, were less likely to develop lung and bladder cancers.
Sauerkraut specifically contains isothiocyanates, compounds produced by fermentation of raw cabbage, which are being studied for anti-cancer properties. The Polish Womens Health Study found that women who ate at least three servings a week of cabbage and sauerkraut were significantly less likely to develop breast cancer than those eating it only once a week.