Fennel

Fennel, botanically Foeniculum vulgare, is a hardy flowering plant of the carrot family (Apiaceae), originally native to the Mediterranean region but now grown and naturalized around the world ^[1]. It is a tall herb with hollow stems, finely divided feathery leaves and yellow flowers arranged in flat-topped clusters known as umbels ^[1]. Several parts of the plant are eaten: the swollen leaf base of Florence fennel is used as a crisp vegetable, the leaves serve as an herb, and the dried fruits, commonly called fennel seeds, are a familiar anise-flavored spice ^[1].

The plant's distinctive aroma and much of its biological activity are attributed to its volatile essential oil ^[1][3]. Analyses of fennel seed oil consistently identify trans-anethole as the dominant constituent, accompanied by fenchone, estragole and limonene among more than a dozen components ^[3]. Fennel also contains phenolic compounds and flavonoids such as rosmarinic acid and luteolin, which contribute to its antioxidant properties ^[1].

Fennel has a long history in traditional medicine across many cultures, where it has been used for digestive complaints such as bloating and colic, as a supposed aid to milk production in nursing mothers, and for menstrual and menopausal symptoms ^[1][2]. Laboratory and animal studies have reported a range of pharmacological actions for fennel extracts, including antioxidant, antimicrobial, anti-inflammatory and antispasmodic effects, and reviews have catalogued its traditional use for dozens of ailments ^[1]. Clinical evidence in humans is more limited; systematic reviews have examined fennel for women's health complaints such as painful menstruation and menopausal symptoms, reflecting continuing interest in testing its traditional uses more rigorously ^[2].

Fennel is generally treated as a food and culinary herb rather than a regulated drug, and it is widely consumed as a vegetable, spice and tea ^[1]. Its essential oil contains estragole, a compound that has prompted some safety discussion at high, concentrated intakes, but ordinary culinary use of fennel is regarded as safe ^[1].

Culinary amounts are very safe. Concentrated fennel oil should be used cautiously and avoided in large amounts during pregnancy because of the estrogen-like activity. Some people with allergies to carrots, celery, or mugwort may cross-react.