About this material
This is an adaptation of the editorial review "How Chaga Can Change Your Health" (MushroomReferences.com, January 2025). It takes a comprehensive look at chaga (Inonotus obliquus) — from the history of folk-medicine use to modern data on bioactive substances and their effects. This review complements the specialized article Chaga: antioxidant and metabolic effects with broader context.
What chaga is
Chaga (Inonotus obliquus) 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 basidiomes form under the bark of the affected tree. 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 USSR State Pharmacopoeia.
Three groups of active substances
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 "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 from the host birch's bark. The content of this group depends on the substrate: a conk that developed on birch is rich in betulin; on another tree it is scarce.
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
The most reproducible finding in laboratory and animal models:
- 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).
Metabolic and anti-inflammatory effects
In animal models of type 2 diabetes, atherosclerosis and metabolic syndrome, chaga extracts:
- lowered fasting glucose and improved glucose tolerance;
- improved lipid-profile markers (lower triglycerides and LDL);
- reduced the severity of hepatic steatosis;
- suppressed NF-κB-pathway activation and lowered pro-inflammatory cytokines (TNF-α, IL-6, IL-1β).
Proposed mechanisms include antioxidant action, AMPK-signalling modulation and effects on the gut microbiota. Translating these results to humans requires clinical confirmation.
Clinical data
As of 2025, the clinical data on chaga consist of:
- Small pilot studies (n = 20–60) with preliminary results on antioxidant status and subjective measures;
- 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.
Antiviral activity
The antiviral direction deserves separate mention. In laboratory work, chaga extracts suppressed the replication of several viruses (including HIV, herpes simplex virus, hepatitis C virus) in cell cultures. This gave rise to a research direction later extended to agarikon, reishi and other wood-decay fungi. Clinical data remain limited.
What is important to keep in mind
- The raw material varies widely. The content of melanins, betulin and polysaccharides depends on conk age, region, forest type, drying and extraction. Comparing commercial products is difficult.
- Extraction method. Water, alcohol and alkaline extracts contain different shares of active substances. Results obtained with one fraction transfer to another only after 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; chaga is listed in the Red Data Books of several Russian regions. Cultivated strains are preferable.
Related materials
- Species card: Chaga (Inonotus obliquus)
- Narrower topic: Chaga: antioxidant and metabolic effects
- Catalog: Mushroom catalog
- Mechanisms: Beta-glucans and immunity, topic Mushrooms and immunity
- Other wood-decay fungi: Reishi, Trametes, Lion's mane, Agarikon
- Sources