# Chaga (Inonotus obliquus)

**Inonotus obliquus**

**Known today as.** A black, cracked, charcoal-like growth on living birch.

Kind: Fungus  
Poisoning: Oxalate poisoning (https://thethinkingpress.org/materia-medica/poisons/oxalate)

> **Caution.** Heavy use can damage the kidneys.

## What was it used for?

Brewed as a tea in Russian and Siberian folk medicine for stomach complaints and cancer.

## What does modern science say?

Heavy use has caused kidney damage from its oxalates. Chaga concentrates betulin from the birch, which has anti-tumour activity in the laboratory, and its oxalate content is among the highest of any organism: a Japanese woman who took it daily for months went into kidney failure, and other patients have been reported since.

## Pharmacognosy and toxicology

- **betulin**: from the birch
- **betulinic acid**: 
- **oxalic acid**: very high

**Mechanism.** Oxalate nephropathy with chronic use.

**Dose.** Months or years of daily use in the reported cases.

## What lore surrounds it?

Its use by poor Russians is mentioned in Solzhenitsyn’s *Cancer Ward*, as Géry and colleagues note.

Among the Potawatomi it is *shkitagen*, the fungus that holds an ember without going out, carried as a fire-keeper.

## What did the older authorities say?

**The Khanty and the Russians.** The Khanty drank it for gastritis and ulcers, and Russian farmers and workers too poor to buy tea drank it as an infusion; the name is from the Komi word for mushroom.

**Soviet medicine.** Recognised its decoction in 1955 and entered it in the Soviet Pharmacopoeia as *Befunginum*.

## Sources

- Kikuchi, Y., et al. (2014). “Chaga mushroom-induced oxalate nephropathy.” *Clinical Nephrology* 81.
- Géry, A., et al. (2018). Chaga (*Inonotus obliquus*), a future potential medicinal fungus in oncology? A chemical study and a comparison of the cytotoxicity against human lung adenocarcinoma cells (A549) and human bronchial epithelial cells (BEAS-2B). *Integrative Cancer Therapies* 17: 832–843.
- Fordjour, E., et al. (2023). Chaga mushroom: a super-fungus with countless facets and untapped potential. *Frontiers in Pharmacology* 14: 1273786.
- Lee, S., et al. (2026). Kidney injury induced by high-dose Chaga mushroom consumption: experimental evidence in a rat model. *Journal of Korean Medical Science* 41: e37.
- Kikuchi, Y., et al. (2014). *Clinical Nephrology* 81.

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*Chaga.* In *Materia Medica*, edited by B. C. P. Statema. Version 1, revised 2026-10-03. The Thinking Press. https://thethinkingpress.org/materia-medica/chaga

Historical description, not medical advice.