Also known as bottle brush, pewterwort, scouring rush, shave grass, and paddock-pipes, some of horsetail’s names allude to its rich content of silica, which makes its aerial parts abrasive and (as it turns out) useful in an industrial sense: In days past, horsetail was used to scour pewter, metals and tableware.
Horsetail’s traditional medicinal uses include balding, hepatitis, jaundice, joint pain, gout, brittle fingernails, osteoporosis, kidney stones, urinary disorders, diabetes, menstrual problems, frostbite, and tuberculosis.
Getting back to modern times – an era marked by sloth, gluttony, and ever-expanding waistlines – we find horsetail (like so many other herbs) being included in any number of weight-loss programs. Although the exact mechanism for horsetail's weight-reducing property remains elusive, it has demonstrated some utility in this regard.
Many weight-loss plans, for reasons that elude rational thought, promote products that help dieters eliminate excess water. While this no doubt makes a person feel good when the scale stops spinning, water weight is just that; although it may be gratifying in the moment, unloading a few pounds of H2O has little bearing on your ultimate weight-control aspirations.
Be that as it may, horsetail appears to be a reasonably good diuretic, and this accounts for at least some of its weight-dropping effects. One 2007 Czechoslovakian study showed that an extract from E. arvense was only slightly less effective than hydrochlorothiazide, a prescription medication used for people with congestive heart failure and other serious water-retention issues. Whether horsetail causes potassium loss like many other diuretics is unclear, so be careful if you tend to run low on your serum potassium level.
For what it’s worth, in 2009 the European Food Safety Authority determined that dried powder from the sterile aerial parts of E. arvense was “sufficiently characterised for the maintenance or achievement of a normal body weight” when used in a daily dose of 400 mg. Alas, the EFSA had no comments on how horsetail works its magic.
Horsetail’s Antioxidant and Anticancer Properties
In the April 2010 issue of “Journal of Medicinal Food,” scientists demonstrated that extracts from E. arvense exerted significant peroxyl scavenging activity in two standard preparations designed to measure antioxidant activity. Horsetail’s antioxidant properties no doubt stem from its flavonoid and catechin content.
These same investigators also measured horsetail’s ability to inhibit the growth of three different human cancer cell lines. In tissue culture, horsetail exerted “antiproliferative” effects – it prevented the growth of cancer cells in a test tube – but any similar benefit in human subjects has not yet been demonstrated.
Horsetail and Diabetes
In 2007, Iranian scientists showed that a methanol extract of E. arvense lowered blood glucose levels in diabetic rats. Interestingly, the rats’ pancreatic beta cells – the place where insulin is made in all mammals – exhibited signs of repair and regeneration following treatment with the horsetail extract.
People who take insulin or other diabetes medications should carefully monitor their blood glucose readings if they choose to take horsetail; the additive effects of your current medications and horsetail could cause dangerous reductions in your blood sugar. Always check with your doctor before taking herbal supplements.
Horsetail and Fingernails
Because it is a rich source of silica, horsetail is often used to treat weak, brittle, or thin fingernails and toenails. Oral preparations of horsetail have never been scientifically proven to improve nail strength…or to improve hair texture, skin health, or bone strength, for that matter.
However, in 2009 Italian scientists tested a topical water-based lacquer containing horsetail and chitosan on the fingernails of patients with psoriasis and found that the "polish" decreased psoriasis-induced nail damage. Not surprisingly, the patients involved in the study were thrilled with the stuff.
Horsetail During Pregnancy
The safety of horsetail during pregnancy has not been adequately demonstrated. Equisetum species contain an enzyme called thiaminase, which degrades thiamine, or vitamin B1. It isn’t clear if long-term use of horsetail causes thiamine deficiency, but pregnant women can't afford to take that chance. Even though some horsetail formulations are labeled “thiaminase-free,” there is no guarantee that they really are.
Horsetail is also a source of nicotine, albeit in small amounts. If you wouldn’t smoke during pregnancy, you probably shouldn’t use horsetail, either.
Horsetail is an ancient plant with a long history of medicinal use, but many of its traditional applications are not supported by scientific evidence. It does appear to be a fairly effective diuretic, it may be useful in some weight-control programs, and it is useful in some topical preparations.
And, you can always use horsetail to put a shine on that old spittoon…
- R Masteiková, et al. An orientational examination of the effects of extracts of mixtures of herbal drugs on selected renal functions. Ceska Slov Farm. 2007;56(2):85-89
- European Food Safety Authority. Scientific opinion on the substantiation of health claims related Equisetum arvense L. EFSA Journ. 2009;7(9):1289-1305
- DD Cetojević-Simin, et al. Antioxidative and antiproliferative activities of different horsetail (Equisetum arvense L.) extracts. J Med Food. 2010;13(2):452-459
- F Cantoresi, et al. Improvement of psoriatic onchodystrophy by a water-soluble nail lacquer. J Eur Acad Dermatol Venereol. 2009;23(7):832-834