Fennel Seed
Foeniculum vulgare
Also known as: Sweet Fennel, Saunf, Finocchio
Overview
A Mediterranean culinary and medicinal herb with powerful carminative properties. Anethole is the primary bioactive responsible for digestive smooth muscle relaxation.
Proposed mechanism
In laboratory and animal studies, trans-anethole inhibits NF-kB signaling, relaxes intestinal smooth muscle through calcium antagonism, and increases bile flow. Its estrogen-related activity is less settled than commonly stated: trans-anethole binds estrogen receptors only at high laboratory concentrations, and the activity is largely attributed to its breakdown products — the metabolite anol, and the dimers dianethole and photoanethole proposed in older animal work — rather than to trans-anethole itself. In small trials in postmenopausal women, topical fennel cream improved vaginal atrophy and sexual-function scores, while oral fennel reduced menopausal symptom scores in some trials but not others. The trials that measured serum estradiol found no consistent change, so fennel is not established as altering hormone levels.
Mechanisms describe how researchers think a compound may act, often from laboratory work — a proposed mechanism is not proof of a clinical effect in people.