Horsetail

Parts used and where grown: Horsetail is widely distributed throughout the temperate climate zones of the Northern Hemisphere, including Asia, North America, and Europe.¹ Horsetail is a unique plant with two distinctive types of stems. One variety of stem grows early in spring and looks like asparagus, except for its brown color and spore-containing cones on top. The mature form of the herb, appearing in summer, has branched, thin, green, sterile stems and looks like a feathery tail.

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

Rating	Health Concerns
	Brittle nails Edema (water retention) Osteoarthritis Osteoporosis Urinary tract infection Wound healing (topical)
Reliable and relatively consistent scientific data showing a substantial health benefit. Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit. An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.

Historical or traditional use (may or may not be supported by scientific studies): Reportedly first recommended by the Roman physician Galen, several cultures have employed horsetail as a folk remedy for kidney and bladder troubles, arthritis, bleeding ulcers, and tuberculosis. In addition, the topical use of horsetail was used traditionally to stop the bleeding of wounds and promote rapid healing. The use of this herb as an abrasive cleanser to scour pots or shave wood illustrates the origin of horsetail’s common names—scouring rush and shave grass.²

Active constituents: Horsetail is rich in silicic acid and silicates, which provide approximately 2–3% elemental silicon. Potassium, aluminum, and manganese, along with fifteen different types of flavonoids, are also found in this herb. The presence of these flavonoids, as well as saponins, is believed to cause the diuretic effect, while the silicon content is thought to exert a connective tissue-strengthening and anti-arthritic action.³ Some experts have suggested the element silicon in horsetail is also a vital component for bone and cartilage formation.⁴ Anecdotal reports suggest that horsetail may be of some use in the treatment of brittle nails.⁵

How much is usually taken? The German Commission E monograph suggests up to 6 grams of the herb per day for internal use.⁶ A tincture can also be used at 2 teaspoons (10 ml) three times per day. A horsetail tea may be made by boiling 2–4 teaspoons of the herb in one cup (250 ml) of water for five minutes. Steep the tea for an additional 15 minutes, strain, and drink two or three times daily. The tea can also be used externally as well as internally.

Are there any side effects or interactions? Horsetail is generally considered safe. The only concern would be that the correct species of horsetail is used. Equisetum palustre is another species of horsetail, which contains toxic alkaloids and is a well-known livestock poison. Due to a lack of clear safety information, horsetail should be avoided during pregnancy and breast-feeding.

The Canadian Health Protection Branch requires supplement manufacturers to document that their products do not contain the enzyme thiaminase, found in crude horsetail, which destroys the B vitamin thiamine. Since alcohol, temperature, and alkalinity neutralize this potentially harmful enzyme, tinctures, fluid extracts, or preparations of the herb subjected to 100°C temperatures during manufacturing are preferred for medicinal use.⁷

Are there any drug interactions? Certain medications may interact with horsetail. Refer to the drug interactions safety check for a list of those medications.

References:

1. Leung AY, Foster S. Encyclopedia of Common Natural Ingredients Used in Foods, Drugs, and Cosmetics, 2nd ed. New York: John Wiley & Sons, 1996, 306–8.

2. Castleman M. The Healing Herbs. Emmaus, PA: Rodale Press, 1991, 219–21.

3. Weiss RF. Herbal Medicine. Gothenburg Sweden: Ab Arcanum, 1988, 238–9.

4. Seaborn CD, Nielsen FH. Silicon: a nutritional beneficence for bones, brains and blood vessels? Nutr Today 1993;28:13–8.

5. Hamon NW, Awang DVC. Horsetail. Canadian Pharm J 1992;September:399–401.

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, 150–1.

7. Fabre B, Geay B, Beaufils P. Thiaminase activity in Equisetum arvense and its extracts. Plant Med Phytother 1993;26:190–7.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2003.