What chaga is
Chaga, or Inonotus obliquus (English names — Chaga, Birch Conk, Clinker Polypore), is a sterile conk of a parasitic fungus developing on living birches, more rarely on alder, rowan and ash. It is a sterile form: the actual basidiomes form under the bark of the affected tree and are usually not visible outside. The conk is black, very hard and cracked; the interior is dark brown with characteristic yellow veins. The species card with the botanical description is at Chaga (Inonotus obliquus).
Chaga has long been used in the folk medicine of Russia, Northern Europe, North America and East Asia. In the 20th century it was included in the official pharmacopoeias of several countries (including the USSR State Pharmacopoeia). Modern scientific interest in chaga centres on three groups of bioactive substances.
What is studied: the main groups of compounds
Melanins
Chaga is one of the most "melanin-rich" fungi: pigments make up a significant share of the conk's dry mass and give it its characteristic black colour. A study published in the journal "Antioxidants" (MDPI) showed that chaga melanins display pronounced antioxidant activity in model systems and cell cultures.
Betulin and betulinic acid
Chaga accumulates betulin and its derivatives — substances contained in the bark of the host birch. Betulin and betulinic acid are studied for anti-inflammatory and cytotoxic effects. Importantly, betulin enters the fungus from birch bark, so the content of this group depends on the substrate the conk developed on.
Polysaccharides
Chaga's polysaccharide fraction consists of β-(1→3)/(1→6)-glucans, structurally close to the fractions of other wood-decay fungi (cf. Beta-glucans and immunity). These polysaccharides are studied as immunomodulating agents.
Antioxidant action
Chaga's antioxidant activity is the most reproducible finding in laboratory and animal models. Main results:
- Reduced oxidative-stress markers. In rodent models, chaga extracts lowered malondialdehyde levels and increased the activity of superoxide dismutase, catalase and glutathione peroxidase.
- DNA protection. In cellular models, chaga melanins and polysaccharides reduced oxidant-induced DNA damage.
- In vitro confirmations. Numerous cell-line studies confirm the antioxidant action of various chaga fractions; a review of these data is in Phytochemistry Reviews (Springer, Inonotus obliquus).
Metabolic effects
Hypoglycemic action
In a series of 2020–2025 studies in animal models of type 2 diabetes (streptozotocin-induced, high-fat diet), chaga extracts:
- lowered fasting glucose and improved glucose tolerance;
- improved lipid-profile markers (lower triglycerides and LDL);
- reduced the severity of hepatic steatosis.
Proposed mechanisms include antioxidant action, AMPK-signalling modulation and effects on the gut microbiota. Translating these results to humans requires clinical confirmation.
Effects on lipid metabolism
In animal models of atherosclerosis and metabolic syndrome, chaga extracts reduced the severity of atherosclerotic changes — attributed to the combination of antioxidant, anti-inflammatory and lipid-lowering actions.
Anti-inflammatory action
In cellular and animal models, chaga extracts lowered pro-inflammatory cytokines (TNF-α, IL-6, IL-1β) and suppressed activation of the NF-κB signalling pathway. These data overlap with Beta-glucans and immunity and the Mushrooms and immunity topic, where the general anti-inflammatory mechanisms of β-glucans are discussed.
Clinical data: what is known
As of 2025, the clinical data on chaga consist of:
- small pilot studies (n = 20–60) with preliminary results;
- observational work in countries where chaga is part of traditional medicine;
- isolated case series.
These materials are summarized in the review "Inonotus obliquus — phytochemistry and bioactivity" on PubMed. Chaga is included in the USSR State Pharmacopoeia and in the pharmacopoeias of several other countries as a medicinal plant.
Context for the data
- Raw-material composition. The content of melanins, betulin and polysaccharides strongly depends on the conk's age, collection site (region, forest type), and on drying and extraction methods. Comparing different commercial products and wild-harvested material is difficult.
- Extraction method. Water, alcohol and alkaline extracts of chaga contain different shares of active substances. Results obtained with one fraction transfer to another only after appropriate verification.
- Safety. Chaga contains oxalates; kidney complications have been reported with prolonged high-dose use. Interactions with anticoagulants, hypoglycemic drugs and immunosuppressants are still being studied.
- Conservation status. Mass harvesting of wild chaga puts pressure on old-growth birch forests. Cultivated strains are preferable.
Where chaga intersects with other fungi in our catalog
- Reishi (Ganoderma lucidum) — a wood-decay fungus with studied β-glucans and triterpenoids; see the reishi card.
- Turkey tail (Trametes versicolor) — another β-glucan source with a clinical history (PSK, PSP); see Trametes versicolor: PSK and PSP.
- Lion's mane (Hericium erinaceus) — a wood-decay fungus with a neuroprotective profile; see Lion's mane and neurogenesis and the lion's mane card.
- Agarikon (Laricifomes officinalis) — a wood-decay fungus studied for antimicrobial activity; see the agarikon card.
What is important to keep in mind
- Chaga is a food and functional raw material. In several countries it is in official pharmacopoeias and used as a medicinal plant; in Russia it is included in the USSR State Pharmacopoeia.
- The raw material varies widely. Chaga quality depends on region, conk age, drying and extraction. Commercial products should be compared by concrete standardization methods (melanin, β-glucan and oxalate content).
- Wild harvesting is limited. Chaga is listed in the Red Data Books of several Russian regions. For regular use, cultivated strains are preferable.
Related materials
- Species card: Chaga (Inonotus obliquus)
- Catalog: Mushroom catalog
- β-glucans: Beta-glucans and immunity
- Topic: Mushrooms and immunity
- Other wood-decay fungi: Reishi, Trametes, Lion's mane, Agarikon
- Sources