Sulforaphane—a compound in broccoli—reduced the number of breast cancer stem cells (which cause cancer spread and recurrence) in mice, according to research from the University of Michigan. Eating broccoli may not deliver enough sulforaphane to achieve the same effect, but to get the most you can, eat your broccoli raw or briefly steam or stir-fry the green florets. (Boiling destroys some of the sulforaphane.)