Herbs (Global Traditional) · European
Equisetum arvense
Moderate Evidencebotanical
Hermetica Superfood Encyclopedia
Horsetail extract (Equisetum arvense) contains high concentrations of silica and flavonoids that support urinary health and blood pressure regulation. Clinical studies demonstrate diuretic effects comparable to hydrochlorothiazide without significant electrolyte imbalance.
Equisetum arvense, commonly known as horsetail, is a perennial herb from the Equisetaceae family native to temperate regions worldwide, including Europe, Asia, and North America. The aerial parts (stems) are harvested during the sterile phase in summer and processed into standardized dry extracts, often standardized to contain specific levels of silica or flavonoids.
Two double-blind randomized controlled trials have evaluated standardized E. arvense extract (900mg/day): one crossover trial (n=36, PMID: 24723963) demonstrated diuretic effects equivalent to hydrochlorothiazide, and another (n=58, PMID: 35168030) showed similar blood pressure reduction in hypertensive patients over 3 months. Additional pilot studies have examined silicon absorption (PMID: 34706374) and topical wound healing applications (PMID: 26019907).
Clinically studied dosage for standardized dry extract: 900mg/day divided into three 300mg capsules, taken for 4 days (diuretic effect) or 3 months (hypertension management). No clinical data available for powder or other forms. Consult a healthcare provider before starting any new supplement.
Equisetum arvense (horsetail) is characterized by exceptionally high silicon (silica) content as its defining nutritional feature. Silica (SiO2) comprises approximately 5–8% of dry weight, present primarily as monosilicic acid and silica gel forms; aqueous tea extraction yields bioavailable monosilicic acid at approximately 4.9 mg Si per 500mL serving (confirmed via ICP-MS, PMID: 34706374). Mineral profile includes potassium (approximately 1.0–2.5% dry weight, relevant to diuretic mechanism), calcium (approximately 0.5–1.2% dry weight), magnesium (approximately 0.1–0.3% dry weight), manganese (approximately 20–50 mg/kg dry weight), and trace iron. Flavonoids present at approximately 0.2–1.0% dry weight, dominated by kaempferol glycosides (kaempferol-3-sophoroside, kaempferol-3-glucoside) and quercetin derivatives, with isoquercitrin identified as a key bioactive contributor to diuretic activity. Phenolic acids include caffeic acid esters (di-E-caffeoyl-meso-tartaric acid, equisetonin) at approximately 0.1–0.5% dry weight. Alkaloids include trace nicotine (0.00004%) and 3-methoxypyridine at low concentrations. Thiaminase enzyme is present in raw plant (destroyed by drying/heat processing). Protein content is low at approximately 2–4% dry weight, consisting largely of structural proteins. Crude fiber constitutes approximately 30–40% dry weight, primarily insoluble silica-bound and cellulosic fractions. Fat content is negligible (<1% dry weight). Ascorbic acid present at approximately 5–7 mg/100g fresh weight. Bioavailability note: silicon absorption from tea form is confirmed and superior to solid extract forms; flavonoid bioavailability is moderate and enhanced by hot aqueous extraction. Thiaminase activity is neutralized in standardized dried/tea preparations used in clinical studies.
Horsetail's silica content and flavonoids including quercetin and kaempferol enhance renal sodium excretion through modulation of aquaporin channels and sodium-potassium pumps. The silica compounds directly affect mineralocorticoid receptor sensitivity, promoting diuresis while maintaining potassium homeostasis. Phenolic compounds provide additional vasodilatory effects through nitric oxide pathway activation.
A randomized controlled trial in 36 healthy males demonstrated horsetail extract's diuretic efficacy equivalent to hydrochlorothiazide 25mg daily without significant electrolyte disturbances. Another study of 58 stage I hypertension patients showed blood pressure reductions of ≥10 mmHg, matching hydrochlorothiazide's antihypertensive effects. Silicon bioavailability studies confirm enhanced resorption from horsetail preparations. Current evidence is promising but limited to small-scale trials requiring larger confirmatory studies.
Horsetail is generally well-tolerated but may cause mild gastrointestinal upset and increased urination frequency. Potential interactions exist with lithium medications due to enhanced renal clearance and with thiazide diuretics due to additive effects. Contraindicated in pregnancy, kidney disease, and heart failure due to fluid-electrolyte concerns. Long-term use may theoretically cause thiamine depletion, though clinical significance remains unclear.
