Chaga
Inonotus obliquus
The birch fungus of the far north, with more than twice the antioxidant capacity of cocoa and a place in the Russian pharmacopoeia.
Overview
It looks like a scorch mark on a birch. Inside, it's gold.
Of all the functional mushrooms, chaga looks least like one. On the trunk of a birch it could pass for a burn scar, so black and cracked that English speakers named it the cinder conk. Split it open and the inside is dense, corky and golden.
That black growth is the sterile conk of Inonotus obliquus, a fungus that lives for decades inside a living birch before breaking through the bark. It draws on the tree's chemistry as it grows, carrying betulin and betulinic acid, the compounds that turn birch bark white, alongside triterpenes, pigments and polyphenols of its own. Foragers across the far north have brewed it for centuries, Soviet medicine registered it, and laboratories are still mapping what it contains.
In figures
- Up to 80 years how long the fungus can live inside a single birch, digesting the heartwood as it grows.
- 10+ years for a conk to grow 10 cm wide. Old ones reach the size of a melon and have to be cut from the trunk with a saw-toothed knife.
- 0 spores from the conk, which is sterile. Chaga fruits only when its tree dies, as a thin crust under the bark that looks like moth-eaten cloth and is soon eaten by insects.
- 1.3 million years since a genome duplication expanded chaga's terpene chemistry. A 2025 study suggests the fungus evolved its own route to betulin, the birch's signature compound.
Other names
In Komi, the language its name comes from, chaga means simply “mushroom”. The names it picked up elsewhere are more vivid.
- Kabanoanatake — Birch mushroom (Japan)
- Shkitagen — The fungus that carries fire (Potawatomi, Great Lakes)
- Tikkatee — Woodpecker tea (Finland)
What it's studied for
- Stimulates macrophages, the immune system's first responders (Lab)
- Calms the mast cells that drive allergic reactions (Animal)
- Protects human cells from oxidative DNA damage (Lab)
- A registered Russian medicine for gastritis since the Soviet era (Clinical use)
- Slows the gut enzyme that turns starch into sugar (Lab)
History of use
Long before chaga reached a supplement shelf, it was a working part of life in the far north.
Western Siberia
The Khanty drank chaga tea for stomach, heart and liver complaints. They also charred it in the fire and broke it into boiling water to make a wash that did the work of soap.
The Great Lakes
The Potawatomi call it shkitagen. Anishinaabe people kept embers alight inside it to carry fire on long migrations, and pounded its fibres into a wool that would take a spark from flint.
1940s · Finland
With coffee scarce during the Second World War, soldiers reportedly brewed chaga in its place. The tea is dark, earthy and bittersweet, with a note of vanilla.
1959 to the early 1960s · Soviet Union
Doctors in Leningrad published their clinical observations of chaga in 1959, and it entered the USSR State Pharmacopoeia in the early 1960s. Its preparation, Befungin, is still a registered medicine in Russia.
1966 · Cancer Ward
Aleksandr Solzhenitsyn wrote chaga into his novel Cancer Ward, in which a doctor writes to a patient about the birch fungus. The book carried chaga’s name around the world.
2024 · Lithuania
A survey of foragers across the country found chaga known in every region and still used at home, often steeped in alcohol.
What's inside the conk
Betulin and betulinic acid
Triterpenes
Betulin is the compound that turns birch bark white, and chaga carries it alongside betulinic acid, its oxidised form. Both have serious pharmacological records. A gel made from birch-bark triterpenes, mostly betulin, is now a licensed medicine in Europe and the US for healing wounds in the skin condition epidermolysis bullosa. A betulinic acid derivative, bevirimat, became the first of a new class of HIV drugs to reach clinical trials.
The fungus makes both compounds itself as well: laboratory cultures of chaga produce them with no tree involved. Levels vary from one conk to the next.
Inotodiol
Triterpenes
Chaga's most abundant triterpene is inotodiol, a compound so characteristic of the fungus that it takes its name from the genus, Inonotus. It has become one of the busiest lines of chaga research. In animal studies inotodiol steadies mast cells, the cells that release histamine, and it eased food allergy and allergic rhinitis in mice.
It is now being developed as a drug candidate, and in 2026 researchers reported that it eased atopic dermatitis in mice.
Polyphenols and melanin
Pigments
The black of the crust is melanin, and the conk is dense with polyphenols. Together they give chaga an antioxidant capacity few foods can match. In ORAC testing, the laboratory yardstick for antioxidant capacity, a water-and-alcohol chaga extract scored around 170,000 µmol TE per 100 g, more than twice the USDA's figure for unsweetened cocoa powder.
In a Japanese comparison of several fungi, chaga's hot-water extract was the strongest scavenger of free radicals tested. In cell studies its polyphenols protected human cells from oxidative damage, and its melanin fed beneficial gut bacteria.
Beta-glucans
Polysaccharides
Chaga carries beta-glucans, the long sugar chains that immune cells recognise, at around 5 to 8% of the raw conk's dry weight, and extraction concentrates them. In a 2024 study from Oslo, two water-soluble fractions of chaga stimulated macrophages through TLR2 and TLR4, the receptors immune cells use to detect microbes.
170,000 ORAC, µmol TE per 100 g
More than twice the antioxidant capacity of unsweetened cocoa powder.
| Chaga, water-and-alcohol extract | 170,000 |
|---|---|
| Unsweetened cocoa powder | 80,933 |
| Blueberries, raw | 4,669 |
Chaga: US Patent 12,514,889. Cocoa and blueberries: USDA ORAC database, 2010.
Why two solvents
Chaga's polysaccharides and melanin dissolve in hot water; its triterpenes barely do. When French researchers analysed a traditional chaga tea, betulin, betulinic acid and inotodiol were all below measurable levels. Alcohol draws them out and lifts the antioxidant capacity with them: in ORAC tests, a water-and-alcohol extract carried close to double the antioxidant capacity of chaga boiled in water for 24 hours. A dual extract, made with both, carries the full chemistry.
Conk or grain?
Plenty of what's sold as chaga is something else. In a 2025 analysis of 18 chaga supplements on the US market, 8 were mycelium grown on grain, with no detectable trace of chaga's characteristic triterpenes and phenolics. Real chaga extract is made from the conk, and its dark melanin is one of the ways laboratories distinguish the two.
The research
Chaga's human research began in Soviet clinics and has reached sports science. The laboratory work behind it runs to hundreds of papers.
Treatment of psoriasis using chaga preparations
Dosychev & Bystrova · 1973 · Human
50 people with psoriasis took a chaga preparation three times a day.
38 cleared and 8 improved, typically within 9 to 12 weeks.
Effect of befungin in peptic ulcer
Fedotov & Rodsolainen · 1981 · Human
58 people with stomach ulcers took Befungin at three doses.
Pain eased, more so at higher doses.
Antioxidant small phenolic ingredients in Inonotus obliquus (Chaga)
Nakajima et al. · 2007 · Lab
Compared the antioxidant activity of several fungi.
Chaga's hot-water extract was the strongest radical scavenger tested.
Anti-allergic effect of inotodiol, a lanostane triterpenoid from chaga mushroom, via selective inhibition of mast cell function
Nguyen et al. · 2020 · Lab and animal
Tested inotodiol on mast cells.
Inotodiol selectively blocked mast-cell activation and allergic reactions.
Structural characterization of chaga polysaccharides and their effects on macrophages
Wold et al. · 2024 · Lab
Separated chaga's polysaccharides and tested them on macrophages.
Two water-soluble fractions stimulated macrophages through TLR2 and TLR4.
Randomised, placebo-controlled crossover trial in cyclists
Nieman et al. · 2024 · Human, randomised and placebo-controlled
20 cyclists took a supplement containing 2.5 g of chaga and cordyceps for two weeks.
Fewer inflammation-related proteins in the blood after 2¼ hours of cycling.
The Soviet studies had no placebo group, and the cyclist trial tested chaga in a blend with cordyceps.
Good to know
Chaga is naturally rich in oxalates, the compounds behind some kidney stones, and there are case reports of kidney damage in people taking 3 to 15 g of chaga powder a day for months. If you have kidney problems, are pregnant or breastfeeding, or take blood-thinning or diabetes medication, check with your doctor first, and stay within the stated dose.
Where you'll find it
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The Mushroom Index
References
- Szychowski KA, Skóra B, Pomianek T, Gmiński J. Inonotus obliquus: from folk medicine to clinical use. J Tradit Complement Med 2021;11(4):293–302.
- Thomas PW, Elkhateeb WA, Daba GM. Chaga (Inonotus obliquus): a medical marvel but a conservation dilemma? Sydowia 2020;72:123–130.
- Safronov O, Bal GL, Sipari N et al. Independent evolution of betulin biosynthesis in Inonotus obliquus. Sci Rep 2025;15(1):21319. DOI
- Drenkhan R et al. Comparative analyses of bioactive compounds in Inonotus obliquus conks growing on Alnus and Betula. Biomolecules 2022;12(9):1178. DOI
- European Medicines Agency. Filsuvez (birch bark extract): European public assessment report, 2022. US Food and Drug Administration approval of Filsuvez, December 2023.
- Smith PF et al. Phase I and II study of the safety, virologic effect, and pharmacokinetics/pharmacodynamics of single-dose 3-O-(3′,3′-dimethylsuccinyl)betulinic acid (bevirimat) against HIV infection. Antimicrob Agents Chemother 2007;51(10):3574–3581.
- Nguyet TMN et al. The mast cell stabilizing activity of chaga mushroom critical for its therapeutic effect on food allergy is derived from inotodiol. Int Immunopharmacol 2018;54:286–295. DOI
- Nguyen TMN, Le HS, Le BV, Kim YH, Hwang I. Anti-allergic effect of inotodiol, a lanostane triterpenoid from chaga mushroom, via selective inhibition of mast cell function. Int Immunopharmacol 2020;81:106244. DOI
- Chung J et al. Inotodiol suppresses allergic inflammation in allergic rhinitis mice. Int Forum Allergy Rhinol 2023;13(9):1603–1614. DOI
- Nguyen TMN et al. CE9A215 (inotodiol) ameliorates oxazolone-induced atopic dermatitis by targeting mast cells and proinflammatory cytokines. J Pharmacol Exp Ther 2026;393(9):104998. DOI
- US Patent 12,514,889. Oxalic acid or oxalate free Inonotus obliquus extract and uses thereof (priority 19 November 2021). ORAC results, Example 1 and Table 6.
- US Department of Agriculture. Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2, 2010.
- Nakajima Y, Sato Y, Konishi T. Antioxidant small phenolic ingredients in Inonotus obliquus (Chaga). Chem Pharm Bull 2007;55(8):1222–1226. DOI
- Cui Y, Kim DS, Park KC. Antioxidant effect of Inonotus obliquus. J Ethnopharmacol 2005;96(1–2):79–85. DOI
- Burmasova MA et al. Melanins of Inonotus obliquus: bifidogenic and antioxidant properties. Biomolecules 2019;9(6):248. DOI
- Wold CW et al. Structural characterization of chaga polysaccharides and their effects on macrophages. Commun Biol 2024;7:233. DOI
- Ying YM et al. Terpenoids with alpha-glucosidase inhibitory activity from the submerged culture of Inonotus obliquus. Phytochemistry 2014;108:171–176. DOI
- Géry A et al. Chaga (Inonotus obliquus), a future potential medicinal fungus in oncology? Integr Cancer Ther 2018;17(3):832–843. DOI
- Windsor C, Kreynes AE, Chilton JS et al. Comparative study of chaga (Inonotus obliquus) dietary supplements using complementary analytical techniques. Int J Mol Sci 2025;26(7):2970. DOI
- Avula B, Katragunta K, Tatapudi KK, Khan IA. Quantitative analysis and simultaneous characterization of triterpenoids and phenolics in Inonotus obliquus (chaga). Planta Med 2026;92(4):494–516. DOI
- Saar M. Fungi in Khanty folk medicine. J Ethnopharmacol 1991;31(2):175–179. DOI
- Kimmerer RW. Braiding Sweetgrass. Milkweed Editions, 2013.
- Zmitrovich IV et al. Chaga and its bioactive complexes: history and perspectives [in Russian]. Formulas of Pharmacy 2020;2(2):84–93. DOI
- Motiejūnaitė J et al. Diversity of ethnomycological knowledge and mushroom foraging culture in a small nation: case of Lithuania. J Ethnobiol Ethnomed 2024;20(1):88. DOI
- Dosychev EA, Bystrova VN. Treatment of psoriasis using chaga preparations. Vestn Dermatol Venerol 1973;47(5):79–83. PubMed
- Fedotov AA, Rodsolainen IuI. Effect of befungin in peptic ulcer. Klin Med (Mosk) 1981;59(7):22–25. PubMed
- Nieman DC et al. Randomised, placebo-controlled crossover trial in cyclists. Front Nutr 2024. DOI
- Kikuchi Y et al. Chaga mushroom-induced oxalate nephropathy. Clin Nephrol 2014;81(6):440–444. PubMed
- Lee S et al. End-stage renal disease after long-term ingestion of chaga mushroom. J Korean Med Sci 2020;35(19):e122. PubMed
- Kwon O et al. Chaga mushroom-induced oxalate nephropathy manifesting as nephrotic syndrome. Medicine 2022;101(10):e28997. PubMed