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Equisetum Arvense
A silica-rich traditional herb marketed for hair, nails, bone, and as a diuretic. Human evidence is thin: one good diuretic RCT and a topical wound-healing trial exist, but the hair/nail/bone claims rest mostly on tradition and in-vitro data. It also contains thiaminase, which can deplete vitamin B1.
What the evidence says
Most Horsetail studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from medium-quality randomised trials published 2011–2015 with a typical study size of 36 participants.
Based on 4 studies · 2 RCTs · 145 total participants
Confidence
LowBy outcome
Horsetail has an evidence score of 2.5/10 — emerging evidence based on 4 indexed studies. A silica-rich traditional herb marketed for hair, nails, bone, and as a diuretic. Human evidence is thin: one good diuretic RCT and a topical wound-healing trial exist, but the hair/nail/bone claims rest mostly on tradition and in-vitro data. It also contains thiaminase, which can deplete vitamin B1. Representative study: PMID 26019907.
The commonly studied dose of Horsetail is Standardized dried extract ~900 mg/day (the diuretic-trial dose); no validated dose exists for hair/nail/bone use. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Explore: Best supplements for Body Health
Last reviewed June 2026 · evidence from 4 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Horsetail (Equisetum arvense) is an ancient plant valued for its high silica content and used traditionally as a diuretic and for hair, nails, skin, and bone. The marketing leans heavily on silicon being a structural mineral for connective tissue, but the actual human evidence is limited and indirect. The strongest data are off-target: a well-conducted Brazilian RCT found a standardized horsetail extract had a genuine diuretic effect comparable to hydrochlorothiazide, and a topical-ointment trial showed faster episiotomy wound healing. For the headline hair/nail/bone claims there are essentially no robust oral human efficacy trials — only in-vitro work (e.g., inhibition of osteoclast formation) and traditional use. A real safety caveat: horsetail contains thiaminase, an enzyme that breaks down thiamine (vitamin B1); chronic use has been linked in a case report to thiamine deficiency, so prolonged or high-dose use is discouraged.
Horsetail is rich in silica; silicon is a structural component of connective tissue, the basis for hair/nail/bone marketing — but oral cosmetic efficacy is unproven.
A standardized extract produced a measurable diuretic effect in a controlled trial, without significant electrolyte loss.
A hydromethanolic extract inhibited human osteoclast formation in cell culture, a theoretical bone-protective mechanism.
How Horsetail works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
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Standardized dried extract ~900 mg/day (the diuretic-trial dose); no validated dose exists for hair/nail/bone use
Take with food
| Form | Type |
|---|---|
| 💊Standardized dried extract (short-term) | Recommended |
| 🧴Topical 3% ointment | Alternative |
Choose thiaminase-managed products; avoid chronic high-dose use.
Minimum: 1 weeks
Optimal: 4 weeks
Cycling: Avoid prolonged continuous use because of thiaminase; use short courses and consider B1 support.
Note: With food; not recommended for prolonged daily use.
Dose-response data unavailable. The current published research for Horsetail does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
A standardized extract produced diuresis comparable to hydrochlorothiazide in healthy men.
A 3% ointment improved episiotomy wound healing and pain — a topical, not oral cosmetic, effect.
The headline oral cosmetic claims are not supported by robust human trials.
Avoid — thiaminase content and a case report linking prenatal use to thiamine deficiency.
Avoid — additive risk of thiamine deficiency.
Use only with medical supervision.
Horsetail has its own diuretic activity; combining with prescription diuretics could increase fluid loss. Monitor.
Diuretic herbs can alter lithium clearance and raise levels. Avoid combining without monitoring.
Thiaminase content can degrade vitamin B1; chronic use may deplete thiamine, especially with poor diet or alcohol.
Tip: Expected diuretic effect; maintain hydration
Tip: Limit duration; supplement thiamine; avoid with alcohol
Both are marketed for hair and nail health via different proposed mechanisms.
Commonly combined in hair/nail formulas (modest evidence for each).
Horsetail is itself a botanical silica source; supplemental silica targets the same connective-tissue rationale.
Overlapping silicon-based structural-support rationale.
Collagen and silica are both promoted for skin, hair, and nail structure.
Layered connective-tissue support (collagen better evidenced than horsetail).
The best time to take Horsetail is with meals. Take it with food. Taken with food; avoid prolonged use because of thiaminase content.
Horsetail should be used with caution — talk to a healthcare provider before taking it. The most commonly reported side effects are increased urination, thiamine (B1) depletion with chronic use. Use caution if any of these apply to you: Pregnancy/breastfeeding (thiaminase; a case report links prenatal use to thiamine deficiency); Thiamine (B1) deficiency or alcohol-use disorder; Use with potent diuretics (additive fluid/electrolyte effects).
Isoflavone-rich plant with weak estrogenic activity that reduces hot flashes and supports bone density and arterial flexibility.