Avocados are not recommended for breast cancer
Avocados (Persea americana) generally are considered a healthy food in the United States; the high fat content of avocados typically is the only reason given for limiting consumption of this fruit. Avocados are a good source of monounsaturated fats, folate, various carotenoids such as lutein and β-carotene, and various chlorophylls. Avocados have been shown to protect the liver, improve cholesterol, and ameliorate osteoarthritis symptoms. Avocado extract has been shown to have chemopreventive effects on human oral premalignant and malignant cells, as well as inhibiting the growth of both androgen-dependent and androgen-independent prostate cancer cell lines in vitro.
Breast cancer-related effects of eating avocados
One study found that a diet high in avocado oil promoted the formation of mammary tumors in rats. Another study of postmenopausal U.S. Latina women found that consumption of avocados was associated with higher circulating estrogen levels. A toxin in avocado leaves has been shown to enhance the cytotoxic effects of tamoxifen on human breast cancer cells regardless of their estrogen receptor (ER) status. Based on the available evidence, breast cancer patients, survivors and those at high risk might do best to limit consumption of avocados until further studies clarify all of these findings.
Additional comments
Lactating animals that gain access to avocado leaves or fruit have been known to develop a type of noninfectious mastitis, with a marked decrease in milk production, and milk characterized by cheesy consistency and clots. This has been shown to be accompanied by pathological changes in the mammary gland. Avocado fruit and leaves have been shown to be toxic to various bird species, dogs, goats, and horses.
Ingesting large amounts of avocado or guacamole can interfere with Warfarin's anticoagulant effect. Up to half of people with a significant latex allergies will develop cross-reactivity to avocados.
Note that while we are continually searching for new evidence concerning this food, there is not much interest in it among cancer researchers so few recent studies are available.