Fennel

Botanical name: Foeniculum vulgare

Photo

© Steven Foster

Parts used and where grown

The fennel plant came originally from Europe, where it is still grown. Fennel is also cultivated in many parts of North America, Asia, and Egypt. Fennel seeds are used in herbal medicine.

Fennel has been used in connection with the following conditions (refer to the individual health concern for complete information):

Science Ratings Health Concerns
2Stars

Colic (in combination with chamomile, vervain, licorice and lemon balm)

Colic (fennel seed oil)

Indigestion and heartburn
1Star

Irritable bowel syndrome
3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.

Historical or traditional use (may or may not be supported by scientific studies)

According to the Greek legend of Prometheus, fennel was thought to have bestowed immortality.1 Fennel seeds are a common cooking spice, particularly for use with fish. After meals, they are used in several cultures to prevent gas and upset stomach.2 Fennel has also been used as a remedy for cough and colic in infants.

Active constituents

The major constituents, which include the terpenoid anethole, are found in the volatile oil. Anethole and other terpenoids inhibit spasms in smooth muscles,3 such as those in the intestinal tract, and this is thought to contribute to fennel’s use as a carminative (gas-relieving and gastrointestinal tract cramp-relieving agent). Related compounds to anethole may have mild estrogenic actions, although this has not been proven in humans. Fennel is also thought to possess diuretic (increase in urine production), choleretic (increase in production of bile), pain-reducing, fever-reducing, and anti-microbial actions.4 Fennel was formerly an official drug in the United States and was listed as being used for indigestion.5

How much is usually taken?

The German Commission E monograph recommends 1–1 1/2 teaspoons (5–7 grams) of seeds per day.6 To make a tea, boil 1/2 teaspoon (2–3 grams) of crushed seeds per 1 cup (250 ml) of water for ten to fifteen minutes, keeping the pot covered during the process. Cool, strain, and then drink three cups (750 ml) per day. As a tincture, 1–2 teaspoons (5–10 ml) can be taken three times per day between meals.

Are there any side effects or interactions?

No significant adverse effects have been reported. However, in rare cases fennel can cause allergic reactions of the skin and respiratory tract.7 Anyone with an estrogen-dependent cancer (e.g., some breast cancer patients) should avoid fennel in large quantities until the significance of its estrogen-like activity is clarified.

Are there any drug interactions?
Certain medicines may interact with fennel. Refer to drug interactions for a list of those medicines.

References

1. Duke JA. CRC Handbook of Medicinal Herbs. Boca Raton, FL: CRC Press, 1985, 145–6.

2. Mills SY. Out of the Earth: The Essential Book of Herbal Medicine. Middlesex, UK: Viking Arkana, 1991, 424–6.

3. Forster HB, Niklas H, Lutz S. Antispasmodic effects of some medicinal plants. Plant Med 1980;40:303–19.

4. Tanira MOM, Shah AH, Mohsin A, et al. Pharmacological and toxicological investigations on Foeniculum vulgare dried fruit extract in experimental animals. Phytother Res 1996;10:33–6.

5. Hare HA, Caspari C, Rusby HH. The National Standard Dispensatory. Philadelphia: Lea & Febiger, 1916, 63, 1129.

6. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 128–9.

7. Blumenthal M, Busse WR, Goldberg A, et al. (eds). The Complete Commission E Monographs: Therapeutic Guide to Herbal Medicines. Boston, MA: Integrative Medicine Communications, 1998, 128–9.