Giant horsetail / Cola de caballo
Equisetum giganteum
Photo credit: Frank Vincentz
Safety information
Safety information
Toxicity: Equisetum contains thiaminase, which breaks down thiamine (vitamin B1); chronic use risks thiamine deficiency (neurological/hepatic harm). Few in-vivo toxicity studies; no consensus non-toxic dose. Heat (~100 C), alcohol and alkaline processing inactivate thiaminase, so properly prepared teas/tinctures are preferred.
Contraindications: Pregnancy and lactation (insufficient data); thiamine deficiency or alcoholism (thiaminase risk); pre-existing electrolyte imbalance/heart or kidney disease (diuretic effect); avoid chronic/high-dose use.
Interactions: Additive fluid/electrolyte loss with diuretics; possible additive potassium loss; caution with lithium (diuretic-type herbs can raise lithium levels); may compound thiamine depletion with alcohol.
Pregnancy & breastfeeding: Pregnancy and lactation: insufficient data — avoid.
Evidence level
Supported by laboratory or animal studies; not yet confirmed in humans.
Preparations
infusion/tea, decoction, fluid extract/tincture (heat/alcohol preparation favored) · aerial stems
Part used: aerial stems
Traditional use: diuretic and for genitourinary disorders, kidney/bladder complaints, diarrhea, heartburn, inflammation
Proposed mechanism: chloroform extract showed diuretic activity in mice comparable to hydrochlorothiazide; high silica/minerals; thiaminase (B1 breakdown)
Dosage note (descriptive only): heat (~100 C), alcohol and alkaline processing inactivate thiaminase
Associated conditions
Nutritional notes
High in silica and minerals but not used as a nutritional food; thiaminase makes raw chronic consumption unsafe.
Healing traditions
Sources (2)
- Horsetail, Drugs.com Natural Products monograph
- Phytochemistry and Pharmacology of the Genus Equisetum (Kidney Diseases), PMC7954623, 2021