Horsetail Extract
A silica-rich herb sold for hair, nails and bone. The silica argument is real; the delivery is the weak link.
Horsetail Extract quick facts
| Suggested dose | 300–900 mg daily of extract, or a choline-stabilized orthosilicic acid product for better absorption. |
| How often | Daily |
| Who it's for | Hair and nail support. Manage expectations. |
Commonly used in hair and nail formulas, where small combination trials show benefit. The specific caution worth knowing: horsetail contains thiaminase, an enzyme that degrades thiamine, and prolonged use has caused B1 deficiency. Thiaminase-free preparations exist. The diuretic effect matters alongside diuretic medication and lithium.
How Horsetail Extract actually works
A silica source, delivering silicon for collagen cross-linking and connective tissue integrity, alongside flavonoids with mild diuretic activity. The silicon must be solubilized to orthosilicic acid to be absorbed, which limits how much is actually bioavailable.
Where to get Horsetail Extract
Find Horsetail Extract on iHerb →The evidence for Horsetail Extract
Graded by what exists behind each claim.
✅ Clinically validated
- A small trial of a horsetail-containing supplement reported improved hair growth — the product contained several other actives, so attribution is impossible.
- Nail and bone trials are essentially absent in humans.
- Has a genuine diuretic effect in small trials, comparable to hydrochlorothiazide in one study.
📊 Correlative data
- Dietary silicon intake correlates with bone mineral density in cohort studies.
🧪 Theoretical / extrapolated benefits
- Silicon participates in collagen cross-linking and connective tissue formation. Whether plant silica is bioavailable enough to matter is the open question.
How to read these tiers: they say how much human evidence exists, not how well something works — and ✗ flags harm, never a disappointing trial. How the evidence tiers work →
What Horsetail Extract actually does
Horsetail is sold for silicon, and the first thing to establish is which chemical form of silicon a plant actually contains. Equisetum arvense accumulates silica as amorphous, polymerized silicon dioxide in its cell walls, which is why the stems are abrasive enough to have been used to scour pots. Polymerized silica is not absorbable. The only form the human intestine takes up is monomeric orthosilicic acid, and getting from one to the other requires depolymerization in the gut Jugdaohsingh 2002.
Silicon's proposed role in connective tissue is a cross-linking role, and the enzymology is genuinely thin. The leading hypotheses are that orthosilicic acid participates in prolyl hydroxylase activity and in the assembly of glycosaminoglycan-collagen networks. No silicon-dependent enzyme has been isolated in humans, and no deficiency syndrome has been described in a person. This is a mineral with an association and without a requirement.
The plant carries a second chemistry that has nothing to do with silicon and is the reason for the safety section. Equisetum contains thiaminase, an enzyme that cleaves thiamine at the methylene bridge, and the classical presentation of horsetail poisoning in grazing animals is a thiamine deficiency picture. That effect belongs to the enzyme, is heat-labile, and is the single most specific pharmacological fact about this plant.
It also has real diuretic activity, which is what it was historically used for. The flavonoid and phenolic fraction — kaempferol and quercetin glycosides, caffeic acid derivatives — drives an increase in urine output that has been reported in controlled human comparison with a thiazide. That is a genuine pharmacological action and it is not what the hair and nail products are sold for.
And the alkaloid content is a species question. Equisetum palustre, a lookalike marsh horsetail, contains the toxic alkaloid palustrine; Equisetum arvense does not, or contains far less. Distinguishing the two is a botanical authentication problem, not a labeling one.
Cell, rodent, human — and where it stops
The chain here has a marker at one end and a different plant at the other, and the two have never been connected.
The absorption end is well measured, for silicon generally. Comparative human work quantified silicon absorption from different foods and supplements and found it varies over an enormous range, with monomeric orthosilicic acid in beer and drinking water absorbed efficiently and polymerized silica from plants and food additives absorbed poorly Sripanyakorn 2009 Jugdaohsingh 2002.
The association end is a cohort. Dietary silicon intake was positively associated with bone mineral density at the hip in men and premenopausal women in the Framingham Offspring cohort Jugdaohsingh 2004. That is an observational association with a nutrient whose main dietary sources are beer, whole grains and root vegetables, which is a familiar confounding problem.
The one randomized bone trial used a completely different material. Choline-stabilized orthosilicic acid, supplied as a stabilized monomer rather than as plant silica, stimulated markers of bone formation in osteopenic women as an adjunct to calcium and vitamin D Spector 2008. The filed label for that product declares 5 mg of silicon as choline-stabilized orthosilicic acid per capsule Office of Dietary Supplements. It is not horsetail.
The obstacle to transfer is the depolymerization step and nobody has measured it for this plant. No published study has given people a standardized horsetail extract and measured serum or urinary silicon against a control. So the whole chain — from capsule to absorbable silicon to tissue to hair — is broken at the first link, and every downstream claim is inherited from a different silicon source.
And the regulator's read on plant silica is the same. The re-evaluation of silicon dioxide as a food additive treats amorphous silica as largely unabsorbed material passing through the gut Younes 2018, which is the correct default assumption for the silica in a plant cell wall.
Horsetail Extract — which form, and does it matter
Three silicon materials are sold and only one of them is reliably absorbed. Choline-stabilized orthosilicic acid is a stabilized monomer and is the material with the randomized bone data Spector 2008 Office of Dietary Supplements. Silicon dioxide and diatomaceous earth are polymerized silica and behave as inert particulates Younes 2018. Horsetail extract is plant-bound silica whose absorbable fraction has not been characterized.
The extraction method decides whether any silicon is released. A hydroalcoholic tincture, a hot-water decoction and a dried powdered herb differ in how much silica is depolymerized to orthosilicic acid, and no label states which process was used or what the resulting absorbable silicon content is. A product declaring 'standardized to 7 percent silica' has declared the unabsorbable form.
Boiling matters for a second reason, and it is the thiaminase one. Thiaminase is a protein and is denatured by heat, so a decoction carries far less thiamine-cleaving activity than a cold-processed powder or tincture. That is a form distinction with a documented clinical consequence, and it is the reverse of the usual assumption that a raw preparation is gentler.
The exposure numbers for the absorbable form are known. Orthosilicic acid is absorbed rapidly, reaching peak serum concentration within about 1.5 to 2 hours, and is cleared quickly by renal clearance with a plasma half-life on the order of 2 to 4 hours Jugdaohsingh 2002 Sripanyakorn 2009. There is no hepatic metabolism, no cytochrome step and no meaningful first-pass extraction; the body handles silicon as an ion to be excreted. Fractional absorption from beer, an efficient source, is around 50 percent, and from a plant-bound source it can be under 5.
What follows from that clock. A once-daily dose of an absorbable silicon source produces a spike and a return to baseline within a day, so any tissue effect depends on chronic repeated exposure rather than on accumulation. And a poorly depolymerized source produces no spike at all, which is a measurement anybody with access to a silicon assay could make in an afternoon.
What would have to be true, and how you would know it was not
1. Predict serum silicon does not rise much after a horsetail capsule. Measure serum or urinary silicon at baseline and 2 hours after a standard dose. Predict a small rise or none, and predict a clear rise after an equivalent dose of choline-stabilized orthosilicic acid Sripanyakorn 2009 Spector 2008. This is the missing experiment and it is a single morning's work.
2. Predict the hair and nail claim fails an objective measure. Predict no measurable change in nail growth rate or in photographic hair density at 6 months, because no controlled trial of horsetail has demonstrated one. A randomized trial with objective measures showing benefit would falsify this page.
3. The prediction that cuts against the product, and it is a safety one. Predict that whole blood vitamin B1 (thiamine) falls, or that the erythrocyte transketolase activation coefficient rises, with sustained daily use of an unheated horsetail preparation, because the plant carries a thiamine-cleaving enzyme. A trial measuring thiamine status through 12 weeks of horsetail and finding it unchanged would falsify this concern, and no such trial exists.
4. Predict a real diuretic effect and the electrolyte consequence of it. Predict increased urine output within days, and predict potassium drifts down over weeks in anybody also taking a thiazide or loop diuretic. Check a chemistry panel at 6 weeks rather than assuming a herbal diuretic is weaker than a pharmaceutical one.
5. Predict the bone marker, if anything, is where a silicon effect would appear. Predict bone formation markers such as osteocalcin respond to an absorbable silicon source over 12 months Spector 2008 and not to a horsetail extract, and predict bone mineral density does not change measurably in either arm inside a year.
What nobody has tested yet
Nobody has measured silicon absorption from horsetail. That is the central gap. Comparative absorption studies covered foods, water, beer and supplements Sripanyakorn 2009 and did not include a standardized Equisetum extract. Until somebody does, the product is sold on a mineral it may not deliver.
There is no marker of silicon status. Serum silicon reflects the last few hours of intake and there is no accepted measure of a tissue pool, so nobody can identify a person who is short of silicon Jugdaohsingh 2002. Without that, no trial can select responders.
The thiaminase risk has never been quantified in people. The enzyme is documented and the veterinary syndrome is well described, and no human study has measured thiamine status through a course of a commercial horsetail product. Given how cheap that measurement is, its absence is striking.
And nobody has surveyed the shelf for species. Equisetum palustre contamination is a recognized botanical hazard and no published market survey has authenticated commercial horsetail products by DNA or by alkaloid profile. That is the same class of problem the rest of this catalog handles with a filed label, and here there is nothing to file Younes 2018.
Horsetail Extract — its own safety story, not its category's
The thiamine risk is the one that is specific to this plant, and it is the reason duration matters. Thiaminase cleaves thiamine, the veterinary syndrome is a thiamine deficiency, and prolonged daily use of an unheated preparation is the exposure pattern that would reproduce it. Anybody with an additional reason for low thiamine — chronic alcohol use, bariatric surgery, a diuretic — is stacking two mechanisms.
The diuretic activity is real and it has electrolyte consequences. Added to a thiazide or a loop diuretic, or taken by somebody on lithium, the effect is additive: dehydration, potassium loss and, for lithium, a concentration change that has a narrow therapeutic window on either side of it.
Nicotine is present in small amounts and it matters for one group. Equisetum contains trace nicotine, which is not pharmacologically relevant for most people and is a reason to keep the product away from children and to avoid it in pregnancy.
Species misidentification is the contamination risk. Equisetum palustre contains palustrine and is a plausible adulterant of an inexpensive wildcrafted herb. A product that does not name the species and its authentication method has not excluded it.
Who should not take it. Pregnancy and lactation, for the nicotine and the absence of data. Anyone on lithium, a diuretic or digoxin, for the electrolyte interaction. Anyone with a history of thiamine deficiency. And anyone buying it for hair or nails, who should know that the randomized silicon evidence belongs to a stabilized orthosilicic acid product rather than to this plant Spector 2008 Office of Dietary Supplements. Nothing here is medical advice or diagnosis, and these statements have not been evaluated by the Food and Drug Administration.
Sources read for this page
- Sripanyakorn S, Jugdaohsingh R, Dissayabutr W, Anderson SH, Thompson RP, Powell JJ. The comparative absorption of silicon from different foods and food supplements. British Journal of Nutrition 2009 · PMID 19356271
- Jugdaohsingh R, et al. Dietary silicon intake and absorption. American Journal of Clinical Nutrition 2002;75(5):887-893 · PMID 11976163
- Jugdaohsingh R, et al. Dietary silicon intake is positively associated with bone mineral density in men and premenopausal women of the Framingham Offspring cohort. Journal of Bone and Mineral Research 2004;19(2):297-307 · PMID 14969400
- Spector TD, et al. Choline-stabilized orthosilicic acid supplementation as an adjunct to calcium/vitamin D3 stimulates markers of bone formation in osteopenic females: a randomized, placebo-controlled trial.. BMC Musculoskeletal Disorders 2008 · PMID 18547426
- Younes M, Aggett P, Aguilar F, et al (EFSA ANS Panel). Re-evaluation of silicon dioxide (E 551) as a food additive. EFSA Journal 2018 · PMID 32625658
- Office of Dietary Supplements, National Institutes of Health. BioSil (Natural Factors) -- filed Supplement Facts panel: silicon 5 mg as choline-stabilized orthosilicic acid (ch-OSA) plus choline 100 mg per capsule, one capsule twice daily; on market. NIH Dietary Supplement Label Database, DSLD ID 220185
How you would know if it worked
There is no blood test for this one. That is not a criticism — it is a fact about the effect, and it changes how you should judge it.
- What to watch: The same growing-edge measurement on hair and nails, with one addition: this one carries a hard stop. The single small positive trial used a product containing several other actives, so attribution is impossible even in the best evidence that exists for it.
- How long before it means anything: Months for anything visible — but do not run it continuously for months. Thiaminase in this plant degrades vitamin B1, documented in livestock and reported in humans, so a long uninterrupted course builds a nutritional problem while you wait for a cosmetic result.
- What will fool you: The diuretic effect is real and early — one small trial compared it to hydrochlorothiazide — so weight and puffiness changes in the first weeks are water and have nothing to do with hair. If silicon is what you are after, choline-stabilized orthosilicic acid has better absorption data and no thiaminase, which makes this the harder route to an easier answer.
Run it one variable at a time. Starting three things in one week means a result you cannot attribute, which is the same as no result.
Horsetail Extract — safety & side effects
- GI upset and, because it is a diuretic, increased urination and potential potassium loss.
- Contains thiaminase, which destroys thiamine (B1). Sustained use can cause thiamine deficiency; only use products labeled thiaminase-free, and take B1 alongside.
- Avoid in kidney disease, and do not combine with diuretics or lithium (diuresis raises lithium levels). Avoid in pregnancy. Contains nicotine in trace amounts.
Not medical advice. If you take prescription medication or have a diagnosed condition, check this against it with a pharmacist or doctor — pharmacists are underused and free.
- When to take it, and what to take it with
- Which form actually absorbs
- Who it's worth it for
- Coach Cam's stacks and notes
- Fasted or with food, and when in the day
- Morning or night, and why that window
- Around training, or deliberately away from it
- What it must not share a window with
Everything above is free and stays free. Skool is where it becomes a plan — Horsetail Extract in an order, with the rest of what you're running.
Unlock in Skool — $10/mo →Bloodwork to run alongside Horsetail Extract
Baseline first, then again at 8–12 weeks.
| Marker | What it’s watching for |
|---|---|
| Ferritin | Below 50 and hair and skin repair suffer, whatever else you take |
| Vitamin D (25-Hydroxy) | Skin, bone and connective tissue all depend on it |
| TSH (Thyroid-Stimulating Hormone) | Thyroid disease shows in hair, skin and nails first |
| Zinc, Plasma | Deficiency causes poor wound healing and hair shedding |
The Basics — Start Here panel covers these in one order — 4 markers, $32.40 with the discount applied.
Check results you already have → · All 103 markers A–Z
Horsetail Extract — frequently asked questions
What is Horsetail Extract?
A silica-rich herb sold for hair, nails and bone. The silica argument is real; the delivery is the weak link.
What is the suggested dose of Horsetail Extract?
300–900 mg daily of extract, or a choline-stabilized orthosilicic acid product for better absorption. This is a general reference for education only — statements have not been evaluated by the FDA and this is not medical advice.
Where can I find Horsetail Extract dosing and the full breakdown?
The suggested dose and the full evidence — clinical, correlative and theoretical — are on this page. What's inside Skool is when to take it, which form actually absorbs, the brand worth buying and Coach Cam's stacks.
Where can I buy Horsetail Extract?
Coach Cam sources Horsetail Extract from vetted, top-rated brands on iHerb — use the buy link on this page.
What Horsetail Extract is used for
Horsetail Extract appears under 1 goal in the goal router.
Related Skin & Structural supplements
Where this goes next
The pages here are the frameworks. The protocols — the dosing, the order to correct things in, the week-by-week schedule and what to retest — are inside Skool.