Chaga

Safety first: kidneys. Case reports describe kidney damage from oxalate (a natural chemical that can form crystals in the kidney) after long-term daily use of chaga powder, in some cases leading to dialysis. [1][2] In one report a biopsy showed oxalate crystals and the leftover chaga had an extremely high oxalate content. [2] People with kidney disease should ask their clinician before using chaga, and anyone who has used it regularly should mention it if their kidney tests are abnormal. Memorial Sloan Kettering Cancer Center (MSK) also advises talking to a healthcare provider about blood thinners such as warfarin. [1] See chaga side effects, oxalates and kidney concerns and kidneys, oxalates and the liver.

What it is

Chaga is Inonotus obliquus (Fr.) Pilát, an accepted species in the family Hymenochaetaceae. [3] MSK describes it as commonly found on birch trees in cold climates. [1] The lump sold as chaga is called a conk; MSK says the medicinal conk comprises wood from the host tree plus mycelium (the thread-like body) of the fungus. [1] A 2022 case report calls it a fungus parasitic on birch and other trees. [4]

This guide gives no harvesting or identification instructions. Wild fungi can look like other species; for any wild mushroom that was eaten, call Poison Help at 1-800-222-1222 in the US.

Traditional use

Traditional use only, not proof. MSK says chaga is used as a folk remedy in Russia and other northern European countries for various ailments, including cancer. [1] It says chaga is edible but not commonly ingested because it is bitter, and that tea made from the whole conk is consumed instead. [1]

What research shows

"Antioxidant" is a lab measurement. It does not show that drinking chaga tea protects the body. See chaga benefits claims checked.

Forms and why the form matters

Chaga is sold as powder, tea, extract and capsules. The case reports MSK lists involved daily powder: 4 to 5 teaspoons daily for 6 months in one woman and 10 to 15 g daily for 3 months, with vitamin C, in a man, and long-term chaga use for skin disease in a third. [1] We do not know how much oxalate other forms deliver, and the sources we read did not compare tea, extract and powder. See chaga tea, powder and extracts. A clinician decides what is right for a person; amounts here describe case reports, not advice.

Conservation

MSK says natural reserves of this fungus have nearly been exhausted and that scientists are seeking cultivated substitutes for wild chaga. [1] Check how a product was sourced; see wild harvest and conservation.

Official statements

The National Cancer Institute's PDQ summary (2024) says the US FDA has not approved medicinal mushrooms to treat cancer or any other medical condition. [5]

Lab data and chemistry

This section is about what laboratories have measured in chaga, not about what chaga does in the body. A lab value shows a compound is there; it does not show a health effect. No open food-composition table (for example USDA FoodData Central) has an entry for chaga, so the numbers below come from research papers that we opened. The part sold as chaga is a sterile conk (also called a canker) on birch, made of host wood plus fungal tissue, not a true mushroom cap. [1][6] One industry-authored paper says that wild conks are about 10 percent fungus by that paper's own citation, and that no chaga has so far been successfully cultivated. [6] That is a claim by authors who sell chaga, and we did not check the cited source.

A. What the laboratory literature reports in this species

Wikidata, which imports the LOTUS natural-products records, lists 97 compounds as found in Inonotus obliquus. [11] Of these, 64 have a ChEBI chemical-database ID and 49 are 30-carbon triterpenoid-type molecules, so triterpenoids are by far the biggest group. [11] The records in the file we used carry no paper reference, so we cannot say which studies sit behind each one. "Reported" means found in at least one study of this species, not present in every product. The table picks the groups most relevant to what is sold; IDs come from the Wikidata file unless stated.

On betulin: one lab separated and measured betulin and betulinic acid in a purified triterpenoid fraction of chaga, [7] while a 2025 comparison found no betulin or betulinic acid in its samples. [6] A 2023 study of lab-grown mycelium argued there is no evidence the fungus makes them itself, and that birch bark is rich in them, [9] whereas a 2025 genome paper abstract proposes the fungus has its own betulin-making pathway. [10] We read only the abstract of the last one. This is unsettled.

B. Measured values

Two sources disagree on betulin (see above). The oxalate figure of 14.2 g per 100 g means about 14 percent of the powder's weight. [2] The Wikidata-sourced IDs are from the file we used; we did not open each ChEBI page.

C. What the numbers do and do not mean

• Ranges move with the host tree, region, harvest, drying and extraction. The six conks in the 2025 study came from five regions on three continents, and the paper reports a spread (for example inotodiol SD 0.080 around a mean of 0.19 percent), so one product's label does not predict another's. [6]


• A compound being present does not show a health effect. Almost all the activity reports for these compounds are in cells or animals; see the table above and [1].


• "Standardised to beta-glucan" depends on the test. The enzymatic assay separates beta-glucan from grain-derived alpha-glucan; a plain total-polysaccharide or starch-based test cannot. [6]


• Fruiting body or conk versus mycelium on grain: in the 2025 study, products made from fungus grown on grain had up to 68 percent alpha-glucan, no detectable chaga triterpenoids and almost no melanin, unlike wild conks. [6] The authors sell conk products, so read this as one industry-authored study. See fruiting body versus mycelium and mycelium on grain.


• Safety numbers matter more than potency numbers here. Oxalate in powders varied several-fold between companies in one report, [2] and the measured caesium-137 in Siberian conks was low in that study, [8] but we found no open data on heavy metals. See mushroom heavy metals and contamination.