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Chaga
CautionSchiefer Schillerporling (Chaga) · (Inonotus obliquus)
Hymenochaetaceae (Hymenochaetaceae)
Description
On birch trunks, Chaga forms a black, cracked growth resembling burnt charcoal – the sclerotium, harvested from October to April, belonging to the Hymenochaetaceae family. It contains beta-glucans, betulin and betulinic acid (absorbed from the birch bark), inotodiol, dark melanin, polyphenols and phytosterols such as ergosterol. In Siberian and northern European folk practice, the crushed sclerotium is prepared as tea or tincture and traditionally used as a general tonic for digestive complaints and to support immunity; an unproven folk application also concerns cancer. Notably, the sclerotium carries a very high oxalate content: chronic use can burden the kidneys, so caution is warranted with kidney disease or kidney stones. Possible interactions exist with anticoagulants and blood-sugar-lowering medication; use is not advised during pregnancy or breastfeeding.
Traditionally the crushed black conk is simmered as a long decoction (tea), drunk in Russian and Siberian folk medicine as a remedy for gastrointestinal complaints and as a general tonic.
Used in Russian folk medicine since the 15th century as a folk remedy against cancer; a curative effect in humans is not scientifically proven.
Alcoholic extracts (tinctures) and dual extracts are used as dietary supplements to capture both water- and alcohol-soluble constituents (triterpenes, polyphenols).
Dried, ground sclerotium is sold as powder or capsules as a dietary supplement; quality varies considerably due to inconsistent processing.
Sources: [1]
Chaga contains very high levels of oxalates (about 2,800-11,200 mg/100 g); chronic use can cause kidney damage (oxalate nephropathy) - avoid with kidney disease or kidney stones. Possible interaction with anticoagulants (e.g. warfarin) and blood-sugar-lowering medication. There is no proven curative effect in humans; do not use as a substitute for medical treatment. Avoid during pregnancy and breastfeeding.
There are no studies in pregnant women. Given the very high oxalate load and the reported kidney damage, chaga is not appropriate during pregnancy.
No data on passage into breast milk. Without such data, and given the known burden on the kidneys, use is not advisable.
Not studied. Relative to body weight, the oxalate load matters even more in children than in adults.
Drug interactions
Gerinnungshemmer und Thrombozytenhemmer
Chaga extract inhibited platelet aggregation in an animal model. An additive effect with anticoagulant medication is conceivable; the clinical relevance is not known.
Blutzuckersenkende Mittel (Antidiabetika)
In vitro, chaga lowered blood sugar in addition to hypoglycaemic agents. Whether this holds in humans is open — with diabetes treatment, keep an eye on blood glucose.
Harvested part: sclerotium (conk)
- Time of day:
- Harvest in winter from living birches, while the sap is up. The black growth is not taken off completely — a remnant stays on the tree so it can regrow, and the bark underneath must not be damaged. Chaga grows over years; a cleanly stripped trunk bears again after a decade at the earliest. On land you do not own, harvesting requires the owner’s permission.
- Drying:
- Break it into walnut-sized pieces while still moist — once dried through, the sclerotium is so hard it is barely possible to break up. Then dry at no more than 50 degrees, or airy in a warm place, until it snaps rather than bends.
- Storage:
- 24 months — Dry, airy and dark. Do not seal it airtight while residual moisture is still in the core — it will mould from the inside.
- Beta-Glucans (polysaccharides)Polysaccharide
Water-soluble beta-D-glucans (up to ~35% in pure extract), immunomodulatory and anti-inflammatory in laboratory studies.
- Betulin / Betulinic acidOther
Triterpenes taken up from the birch host, with proapoptotic effects in laboratory studies.
- InotodiolOther
A lanostane triterpenoid studied for cytotoxic and anti-inflammatory activity.
- MelaninOther
High melanin content gives the sclerotium its black colour; antioxidant properties.
- Polyphenols / phenolic acidsPhenolic acid
Phenolic compounds with antioxidant properties.
- Phytosterols (ergosterol, lanosterol)Other
Sterols present as secondary constituents.
- OxalatesOther
Very high concentrations - relevant for safety (kidneys).
- [3]MonographTherapeutic properties of Inonotus obliquus (Chaga mushroom): A review (PMC11132974)(accessed: 2026-05-31)
- [5]MonographChaga Mushroom — About Herbs, Memorial Sloan Kettering Cancer Center(accessed: 2026-08-22)
- [1]WikipediaInonotus obliquus — Wikipedia (English)(accessed: 2026-05-31)
- [2]WikipediaSchiefer Schillerporling — Wikipedia (Deutsch)(accessed: 2026-05-31)
- [4]CommonsFile:Inonotus obliquus, Finland.jpg — Wikimedia Commons(accessed: 2026-05-31)