The Fennel Herb and Estrogen

Fennel is a flavorful plant used extensively in herbal medicine and in cooking. The plant's fibrous bulb is eaten as a vegetable, while its seeds are used as seasonings and supplements. Fennel owes its licorice-like flavor to natural plant compounds which are similar to the hormone estrogen. Fennel's exact effects on the human body are poorly understood, but it may raise levels of estrogen if it is consumed in large amounts.

Plant Compounds

Fennel contains a complex of estrogen-affecting compounds. An evaluation published in the "Journal of Enthnopharmacology" found that fennel's primary estrogen-like compounds include anethole, photoanethole and dianethole, which it shares with similar-tasting plants, such as licorice root, anise and star-anise. When used in small quantities as flavoring agents, these compounds are generally recognized as safe, by the Food and Drug Administration.

Estrogenic Effects

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Estrogen-like plant compounds, such as those found in fennel, have a notable effect on human hormones. The "Journal of Ethnopharmacology" notes that fennel has a long history of use as a treatment for lactation problems, infertility and pregnancy complications. The "Journal of Integrative Cancer Therapies" notes that these plant compounds may impact hormone levels in women with estrogen-sensitive conditions such as breast cancer and ovarian cancer. However, scientists are not yet certain whether these hormonal effects are beneficial or detrimental to women with these disorders.

Breast Development

Herbal supplement manufacturers frequently advertise fennel, without FDA approval, as a natural breast enhancer. MayoClinic.com physician Sandhya Pruthi strongly urges against the use of these products, noting that there is insufficient evidence of their safety or efficacy. It is, however, plausible that fennel's estrogen-altering can increase breast size. Renowned lactation expert Kelly Bonyata recommends the herb to nursing women as a galactagogue, or breast milk enhancer. When given fennel tea as a colic remedy, many babies have experienced thelarche, or premature breast development, according to the "Journal of Pediatric Surgery." These findings suggest that medicinal amounts of fennel affect breast tissue.

Potential Dangers

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Fennel used as a food does not generally cause side effects or notable changes in hormone levels. However, medicinal quantities may pose a danger. In addition to causing alarming development of secondary sex characteristics in children, large quantities of fennel can also increase the risk of some forms of cancer. Fennel's hormonal effects could also influence fertility, pregnancy and hormone-sensitive cancers. Until scientists understand more about fennel's pharmacological effects, do not use fennel as a medicinal food without consulting your doctor.