Horsetail
Also known as: Equisetum arvense, Field horsetail, Shavegrass
The prehistoric silica herb — a traditional diuretic and hair-nails-bones tonic with real silicon content and real caveats.
In short
Horsetail (Equisetum arvense) is a living fossil of a plant — its family predates the dinosaurs — and one of the richest plant sources of silica, the mineral form of silicon used in hair, nail, and bone support. As an herb it has two traditional identities: a mild diuretic (with German regulatory recognition for urinary flushing) and a remineralizing tonic for bones, hair, and nails. The evidence is mixed — small studies show nail brittleness improvement and modest bone-marker effects, but rigorous trials are thin. Its cautions are specific and worth knowing: it contains thiaminase (which can deplete vitamin B1 with heavy use) and its potassium-sparing diuretic effect can interact with medications.
- Ancient plant; richest botanical silica source
- Traditional diuretic + hair/nail/bone tonic
- Small trials: nail strength, bone markers — thin overall
- Contains thiaminase; B1 depletion with heavy use
What is Horsetail?
Horsetail has been growing since before the dinosaurs and being used medicinally for nearly as long as humans have kept records. Its modern relevance comes down to one element: silicon, concentrated in the plant as silica and implicated in the cross-linking of collagen and the mineralization of bone. That chemistry gives horsetail its two lives — as a gentle urinary-flushing diuretic and as a hair-nails-bones tonic — and its caveats: a thiaminase enzyme that can deplete vitamin B1 and a diuretic effect that deserves respect around medications.
Where it comes from
Natural sources
- Aerial parts of Equisetum arvense, a primitive spore plant found worldwide
- Traditional European diuretic and wound remedy
- Contains 5–8% silica, flavonoids, and the enzyme thiaminase
How it's made
Dried herb teas, capsules, and standardized silica extracts.
What it does in products
Benefits
Nail and hair strength
emerging evidenceSmall trials report reduced nail brittleness and improved hair strength, consistent with silicon's connective-tissue role — though effect sizes are modest.
Bone support
emerging evidencePreliminary studies in osteopenic women show positive bone-marker trends; evidence trails the ch-OSA silicon trials it inspired.
Urinary flushing (traditional)
moderate evidenceRecognized in Germany as a supportive diuretic for urinary-tract flushing — traditional use with modest clinical support.
Side effects & safety
Safety considerations
- Avoid — traditional use associates horsetail with uterine activity, and alcohol-containing extracts are unsuitable.
- Diuretics — additive effects and possible potassium interactions
- Lithium — diuretic-induced lithium retention risk, as with all diuretics
- Not for: Pregnancy
- Not for: Heart or kidney conditions requiring diuretic management
- Not for: Thiamine deficiency
How it's used
In supplements
Standardized extracts supplying 10–40 mg silica/day; traditional tea 1–4 g herb daily. Prefer heated preparations (tea) or thiaminase-free extracts.
In skincare
Occasional extract in hair products; no standard concentration.
Regulatory status
- Sold as a dietary supplement; licensed herbal diuretic in Germany.
- Not applicable.
Popular products containing Horsetail
- NOW Horsetail Extract — Silica-standardized capsulesNOW Foods · Supplement
- Nature's Way Horsetail — Dried aerial parts capsulesNature's Way · Supplement
- Traditional Medicinals / herbal tea blends — Horsetail-containing teasTraditional Medicinals · Supplement
Product names and brands are shown for reference and belong to their respective owners.
The silicon connection
Silicon cross-links collagen and supports bone mineralization — and horsetail is its richest botanical source. The plant's hair-nail-bone reputation maps onto silicon biology, but the delivered dose depends on the silica's bioavailability, which varies by preparation. Purified orthosilicic-acid supplements (ch-OSA) deliver the mineral more predictably.
The thiaminase warning
Raw horsetail contains thiaminase, an enzyme that breaks down vitamin B1 — heavy use of raw preparations can induce deficiency. Heating (as in tea preparation) inactivates the enzyme, and many commercial extracts are thiaminase-tested. This is a classic example of preparation method deciding safety.
Frequently asked questions
Does horsetail really grow hair?
It improves hair strength and brittleness modestly in small studies, but there is no evidence it reverses pattern hair loss.
Is horsetail safe as a daily tea?
Moderate tea consumption is traditional and lower-risk (heat inactivates thiaminase), but it is a diuretic — stay mindful of fluid balance and medications.
Should I take horsetail or a silica supplement?
If the goal is silicon for connective tissue, purified ch-OSA delivers the mineral more predictably. Horsetail suits those preferring a traditional herb, in safe preparations.
The bottom line
Horsetail is a silica-rich living fossil with genuine traditional credentials and modest, mostly preliminary evidence — best used in heated or standardized forms that respect its thiaminase caveat.
References
- Horsetail (Equisetum arvense): pharmacology review. PubMed Central. https://pubmed.ncbi.nlm.nih.gov/29199676/
- Horsetail in bone health. PubMed. https://pubmed.ncbi.nlm.nih.gov/30940342/
- Horsetail — NCCIH. NCCIH. https://www.nccih.nih.gov/health/horsetail