A new study from Boston University School of Medicine reveals that African American women who eat more vegetables have a reduced risk of estrogen receptor-negative breast cancer than women who eat few vegetables.
Statistics from the National Cancer Institute’s Surveillance and Epidemiology End Results (SEER) review tell the story: while the incidence of breast cancer is highest among white women when compared with African American, Asian, Hispanic, and Native Americans, the women most likely to die of the disease are African American. For example, the death rate from breast cancer among white women is 23.4 per 100,000 women while it is 32.4 among African American women and 15.3 among Hispanic women.
Investigators from the Slone Epidemiology Center at Boston University School of Medicine followed 51,928 women for 12 years who participated in the Black Women’s Health Study. During that period, 1,268 women developed breast cancer. Among those for which the hormone receptor status was known, 35 percent were estrogen receptor-negative/progesterone receptor-negative (ER-/PR-). When diet was evaluated, it was found that the incidence of ER-/PR- breast cancer was 43 percent lower among women who ate at least two vegetables daily compared with those who ate fewer than four vegetables per week.
Breast cancers that have estrogen receptors are classified as “estrogen receptor-positive” while those that do not have estrogen receptors are called “estrogen receptor-negative.” In women who have estrogen receptor-positive cancers, the cancer cell growth is controlled by estrogen, and so those women are usually treated with tamoxifen, a drug that blocks the interaction between estrogen and the receptor.
Estrogen receptor-negative cancer does not respond to tamoxifen, is more challenging to treat, and has a poorer prognosis. African American women are more likely than white women to have estrogen receptor-negative tumors.
Therefore, African American women who increase their intake of vegetables may help decrease their risk of breast cancer. The study’s authors reported that high consumption of cruciferous vegetables (e.g., broccoli, cabbage, mustard greens, cauliflower, watercress, kale) especially may be associated with a reduced risk of breast cancer. One reason is because these vegetables contain glucosinolates, which have an impact on estrogen metabolism and enzymes involved in detoxification.
Other studies have indicated that cruciferous vegetables are helpful in fighting cancer. Results of the recent Women’s Healthy Eating and Living Study found that vegetable consumption, especially cruciferous ones, may be associated with a reduced risk of breast cancer recurrence or new events particularly for women using tamoxifen. Another study found the component benzyl isothiocyanate in cruciferous vegetables inhibited breast cancer cell growth.
Increasing vegetable intake, particularly cruciferous varieties, may play an important role in reducing the risk of breast cancer among African American women. The study’s authors also found that carrots, which are high in antioxidant carotenoids, may contribute to reduced breast cancer risk as well.