Fruit and Vegetable Intake in Relation to Risk of Breast Cancer in the Black Women's Health Study

Fruits and vegetables are rich sources of carotenoids, flavonoids, and glucosinolates, which are potentially protective against cancer (1–3). Numerous studies have examined the association between fruit and vegetable consumption and breast cancer risk, but results have been inconclusive. A pooled analysis of 8 cohort studies found no overall association between fruit and vegetable intake and breast cancer risk (4). The European Prospective Investigation into Cancer and Nutrition study also had null findings for total fruit and vegetable intake (5). However, there is some evidence that specific subclasses of vegetables, such as cruciferous and carotenoid-rich vegetables, may be inversely associated with risk of breast cancer (6–8). Molecular subtypes of breast cancer may have biologically distinct etiologies (9, 10), and there is increasing evidence that breast cancer risk factors may differ by breast cancer subtype (11–14). Four epidemiologic studies have examined the association between intake of fruits and vegetables and breast cancer risk according to estrogen receptor (ER) or progesterone receptor (PR) status. Two cohort studies reported an inverse association between fruits and vegetables and ER-negative (−) but not ER-positive (+) breast cancer (15, 16), whereas 2 case-control studies observed an inverse association with ER+ but not with ER− breast cancer (17, 18). African-American women are more likely than white women to be diagnosed with ER−/PR− tumors, which are associated with increased 5-year mortality (19). Although black women consume fewer vegetables overall than white women (20), they tend to consume greater amounts of cruciferous vegetables (21). No epidemiologic studies have assessed breast cancer risk in relation to fruit and vegetable intake separately among African-American women. However, in our report from the Black Women's Health Study, we found that a “prudent” dietary pattern—rich in vegetables, fruits, whole grains, and fish—was inversely associated with both premenopausal breast cancer and ER−/PR− breast cancer among African-American women (22), consistent with results from previous studies (23). In the present report, we investigated whether fruit and vegetable intake accounted for the association of breast cancer risk with a prudent dietary pattern in the Black Women's Health Study. In addition, because specific fruits and vegetables may have an important protective effect, we evaluated the relation between subclasses of fruits and vegetables and breast cancer risk.