Researchers at Boston University Medical Center tracked 51,928 study participants at the Boston University School of Medicine for 12 years, during which time 1,268 cases of breast cancer developed.
Among the breast cancer cases on which hormone receptor status was obtained, 35 percent were estrogen receptor-negative/progesterone receptor-negative breast cancers.
The study, published in the American Journal of Epidemiology, finds the incidence of estrogen receptor-negative/progesterone receptor-negative breast cancer was 43 percent lower among women consuming at least two vegetables per day compared with women who ate fewer than four vegetables per week.
African-American women are more likely than white women to be diagnosed with estrogen receptor-negative tumors, which has a poorer prognosis than estrogen receptor-positive tumors, the researchers say.
High intake of cruciferous vegetables in particular -- broccoli, mustard and collard greens, and cabbage -- may be associated with reduced risk of breast cancer overall, the study says.