Horsetail

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.

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

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

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.

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

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.