Studies have not established the effect of fennel on breast cancer

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Effect of fennel on breast cancer not established
Fennel (Foeniculum vulgare) belongs to the umbelliferae family, which also includes carrots, celery, dill, parsnips, parsley, cumin, and coriander. All parts of the fennel plant are edible (bulb, stalk, leaves and seeds). Fennel is a dietary source of vitamin C and fiber. Fennel bulbs and leaves also contain myricetin and various other phytochemicals, including limonene, rutin, quercetin, and kaempferol, all of which have demonstrated chemopreventive activities. Fennel seeds also contain some gallic acid and melatonin.
Fennel contains the terpenoid anethole, which has been reported to have both estrogenic and chemopreventive effects, as well as estragole, which acts as a rodent carcinogen in large doses. Fennel has been shown to have antioxidant, antifungal, antibacterial and antithrombotic properties.
Fennel seed tea and other fennel preparations have been used in some traditional medicine systems to sooth colic in babies, and to help expel gas and treat indigestion in adults. Other traditional uses include enhancing breast milk production, promoting menstrual flow, easing childbirth, and inducing abortion. Extracts of fennel have been shown to be induce melanoma and liver cancer cell death. A fennel seed diet was shown to prevent carcinogen-induced skin cancer in mice in another study.

Breast cancer-related effects of consuming fennel

Information concerning fennel consumption as it relates to risk of breast cancer is limited. Fennel extract has been shown to be cytotoxic to human breast cancer cells. Fennel seed is a source of melatonin, which protects against breast cancer in several ways, including by reducing aromatase activity within the breast, thereby reducing estrogen production. Fennel seed compound gallic acid has been shown to increase the effectiveness of Taxol chemotherapy in hormone receptor positive (ER+/PR+) breast cancer cells.
However, reports that fennel has been used to increase breast milk production are concerning because they suggest that fennel acts directly on breast tissue. Fennel has been shown to have estrogenic and progesterone-binding properties, although not all studies agree on this. Until more information becomes available, it appears inadvisable for breast cancer patients, survivors and those at high risk to consume more than modest amounts of fennel, fennel seed, or fennel seed tea. Fennel oil should be avoided.

Additional comments

Women who are pregnant or nursing should not consume fennel or fennel seed since fennel can stimulate the uterus.
Fennel has been shown to impair the absorption of the antibiotic ciprofloxacin (Cipro) and in all likelihood would interfere similarly with other fluoroquinolone antibiotics.
Note that while we are continually searching for new evidence specifically concerning this food, there is not much interest in it among breast cancer researchers, so few studies are available.

Selected breast cancer studies

Gallic acid potentiates the apoptotic effect of paclitaxel and carboplatin via overexpression of Bax and P53 on the MCF‐7 human breast cancer cell line Myricetin induces apoptosis mediated by oxidative stress in 4T1 and E0771 mammary cancer cells The Effect of Fennel and Black Seed, on Breast Milk, Prolactin Levels and Anthropometric Index in Human and Animal Samples: A Review Association between flavonoids, flavonoid subclasses intake and breast cancer risk: a case-control study in China Foeniculum vulgare (Fennel) Effects on Puberty Timing, Reproductive Function and Behaviour in Adult Female Mice Following Neonatal Exposure Myricetin-induced apoptosis of triple-negative breast cancer cells is mediated by the iron-dependent generation of reactive oxygen species from hydrogen peroxide Myricetin suppresses breast cancer metastasis through down‐regulating the activity of matrix metalloproteinase (MMP)‐2/9 Chloroform fraction of Foeniculum vulgare induced ROS mediated, mitochondria-caspase-dependent apoptotic pathway in MCF-7, human breast cancer cell line Myricetin Inhibits Angiogenesis by Inducing Apoptosis and Suppressing PI3K/Akt/mTOR Signaling in Endothelial Cells Effect of Foeniculum vulgare (fennel) on vaginal atrophy in postmenopausal women: A double-blind, randomized, placebo-controlled trial Cytotoxicity of the Essential Oil of Fennel (Foeniculum vulgare) from Tajikistan Ovarian protection in cyclophosphamide-treated mice by fennel Enhanced oral bioavailability of docetaxel in rats combined with myricetin: In situ and in vivo evidences Protective Effects of Essential Oils as Natural Antioxidants against Hepatotoxicity Induced by Cyclophosphamide in Mice Myricetin arrests Human Telomeric G-quadruplex structure: A new mechanistic approach as an anticancer agent Apiaceae seeds as functional food Potent Chemopreventive/Antioxidant Activity Detected in Common Spices of the Apiaceae Family Intake of selected bioactive compounds from plant food supplements containing fennel (Foeniculum vulgare) among Finnish consumers The Effect of Herbal Tea Containing Fennel Seed on Breast Milk Sufficiency Signs and Growth Parameters of Iranian Infants A striking and frequent cause of premature thelarche in children: Foeniculum vulgare