Herbs & Supplements:
Horsetail
Equisetum arvense

Principal Proposed Uses
  • Brittle Nails, Osteoporosis, Rheumatoid Arthritis

Horsetail is a living fossil, the sole descendent of primitive plants that served as dinosaur snacks 100 million years ago. The herb is unique for its high concentration of silicon, as well as for its ability to dissolve gold and other minerals into itself. Because of its silicon content, horsetail is abrasive enough to be used for polishing.

Medicinally, horsetail has been used for treating urinary disorders, wounds, gonorrhea, nosebleeds, digestive disorders, gout, and many other conditions.¹

What Is Horsetail Used for Today?

Silicon plays a role in bone health,² and for this reason, horsetail has been recommended to keep bones and nails strong. The famous German herbalist Rudolf Weiss also suggests that horsetail can relieve symptoms of rheumatoid arthritis.³ However, there is no real scientific evidence for any of these uses.

Dosage

The standard dosage of horsetail is 1 g in capsule or tea form up to 3 times daily, as needed. Medicinal horsetail should not be confused with its highly toxic relative, the marsh horsetail (Equisetum palustre)

Safety Issues

Noticeable side effects from standard dosages of horsetail tea are rare. However, horsetail contains an enzyme that damages vitamin B₁ (thiamin) and has caused severe illness and even death in livestock that consumed too much of it.⁴ In Canada, horsetail products are required to undergo heating or other forms of processing to inactivate this harmful constituent.

Also, perhaps because horsetail contains low levels of nicotine, children have been known to become seriously ill from using the branches as blow guns.⁵ This plant can also concentrate toxic metals present in its environment.

For all of the above reasons, horsetail is not recommended for young children, pregnant or nursing women, or those with severe kidney or liver disease.

Individuals taking the medication lithium should use herbal diuretics such as horsetail only under the supervision of a physician, as being dehydrated when taking this medication can be dangerous.⁶

Horsetail may also cause loss of potassium, which may be dangerous for those taking drugs in the digitalis category.^7,8

Interactions You Should Know About

If you are taking

• Drugs in the digitalis category: Use horsetail only under medical supervision.
• Lithium: Do not use horsetail except under the supervision of a physician.

Last reviewed March 2002 by Medical Review Board

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