Research review
Chaga mushroom: what the research does and doesn't show
A map of every chaga study we found: no human trials, two case reports of kidney harm, and lab work on human cells and animals.
No human trial shows that chaga mushroom does anything. A PubMed search on 2 October 2026 found no clinical trial, observational study or meta-analysis of Inonotus obliquus in people. The human record is two case reports of kidney harm, plus human blood cells tested in a dish. This page maps every type of study that exists.
What the evidence doesn't support
It does not support any benefit of chaga at any dose, because no dose has been tested in a controlled human study. It does not support treating a cell-dish result as a result in a person: in the two lab studies below, nobody swallowed anything. And it does not support carrying findings from the hard black conk, which most chaga research and most chaga tea describe, over to mycelium grown on grain or to a powder of unknown origin. A 2025 analysis found grain-fermented chaga mycelium products chemically very different from conk (PMID 40243601). The narrative version of this is on chaga benefits: what the research does and doesn't show; this page is the inventory.
What the trials found
There are no trials. The table lists every study type we found, grouped by what actually happened to whom. We searched PubMed on 2 October 2026 for Inonotus obliquus or chaga combined with the clinical trial, randomized controlled trial, observational study and meta-analysis publication types, and the search returned zero records. Certainty is stated for the question "does chaga do something good in a person who takes it".
| Study | Who or what | Dose and form | Duration | Result | Certainty |
|---|---|---|---|---|---|
| People who swallowed chaga (case reports only) | |||||
| PMID 35451393 (2022) | One 69-year-old man | 10-15 g a day of chaga powder plus vitamin C 500 mg a day | About 3 months | Acute kidney injury with calcium oxalate crystals in the kidney; function recovered about a month after treatment began | None for benefit; one case of harm |
| PMID 32419395 (2020) | One 49-year-old man taking it for a skin condition | Chaga powder, daily dose not stated; leftover powder assayed at 14.2 g oxalate per 100 g | About 5 years | End-stage kidney disease with oxalate deposits on biopsy | None for benefit; one case of harm |
| Human cells, nobody ingested anything | |||||
| PMID 18997282 (2007) | White blood cells from 20 people with inflammatory bowel disease and 20 healthy volunteers | Ethanol extract, 10-500 micrograms per mL, applied to cells | In a dish | Hydrogen-peroxide DNA damage was 54.9% lower in the patient cells and 34.9% lower in the healthy cells | Very low: a dish is not a body |
| PMID 15630179 (2004) | Human white blood cells | Water extract, 10-500 micrograms per mL, applied to cells | 1 hour before peroxide | Over 40% less DNA fragmentation than the peroxide-only control | Very low |
| Animals and lab assays | |||||
| PMID 41555803 (2026) | Rats | Powder at 1,281.6 or 3,844.8 mg per kg body weight, scaled from a human case | Not stated in abstract | At the higher dose: kidney tubular injury, oxalate crystals, more urinary protein and oxidative-stress markers | Animal data on harm; no human dose |
| PMID 16289471 (2006) | Platelets in the lab; mice | Mycelium ethanol extract and a purified peptide | Not stated | Less platelet clumping in the lab (81.2% at best) and in mice | Very low; relevant as a caution about blood thinners |
| Reviews and product analyses | |||||
| PMID 34195023 (2021) | Narrative review of mostly cell and animal work | Mostly extracts | Varied | The authors conclude that studies meeting evidence-based medicine criteria are needed | Not a trial |
| PMID 40243601 (2025) | Chaga conk, mycelium and supplements, analysed in the lab | Not applicable | Not applicable | Grain-fermented products were starch-rich and chemically very different from conk; the authors work for a conk supplier | Not a human study |
Where the evidence is, and isn't
The evidence is in two places: lab work on extracts, and two reports of kidney damage in people eating large amounts of powder. It is not in controlled human studies, because there are none. Chaga is naturally high in oxalate, which is why the harm reports matter more than the dish studies. A case report cannot say how common the problem is, and neither case tells you what a small daily amount of a mycelium powder would do. For the safety narrative, see chaga mushroom side effects and who should not take chaga mushroom.
Questions people ask
Can chaga mushrooms cause diarrhea?
No study we found reports diarrhea from chaga, so we cannot say how often it happens or whether it does. The only human outcomes on record are the two kidney cases above, and neither is a controlled study. If you have digestive symptoms after taking any new supplement, stop and ask a doctor or pharmacist.
Are chaga mushrooms safe during pregnancy, while breastfeeding, or for kids?
We found no study of chaga in pregnancy, breastfeeding or children, so nothing here can tell anyone it is safe, and this page gives no guidance on any of them. If you are pregnant, nursing or choosing for a child, ask a doctor before using a chaga product.
Does chaga mushroom interact with medicines?
The only evidence is a lab and mouse study of platelet clumping (above). It is not a human interaction study. See chaga mushroom and medications and talk to a pharmacist if you take a blood thinner.
When to talk to a doctor
Chaga is not a treatment for any condition, and nothing above supports using it as one. If you have kidney disease or a history of kidney stones, or you take blood thinners or blood-sugar medicine, talk to a doctor before taking any chaga product. Seek care promptly for reduced urine, swelling, or flank pain while taking chaga.
Sources
- Comparative Study of Chaga (Inonotus obliquus) Dietary Supplements Using Complementary Analytical Techniques Lab analysis of chaga supplements found grain-fermented mycelium products chemically very different from wild chaga conk, and starch-rich.
- Chaga mushroom-induced oxalate nephropathy that clinically manifested as nephrotic syndrome: A case report A 69-year-old man taking 10-15 g a day of chaga powder plus vitamin C for 3 months developed acute kidney injury with oxalate crystals; he recovered with treatment.
- Development of End Stage Renal Disease after Long-Term Ingestion of Chaga Mushroom: Case Report and Review of Literature A 49-year-old man who took chaga powder for years ended up with end-stage kidney disease and oxalate deposits; the leftover powder was very high in oxalate.
- Chaga mushroom extract inhibits oxidative DNA damage in lymphocytes of patients with inflammatory bowel disease In white blood cells from 20 patients and 20 healthy people, a chaga extract added to the dish reduced induced DNA damage; nobody swallowed any chaga.
- Chaga mushroom extract inhibits oxidative DNA damage in human lymphocytes as assessed by comet assay An aqueous chaga extract reduced peroxide DNA damage in human white blood cells in a dish; no one swallowed anything.
- Kidney Injury Induced by High-Dose Chaga Mushroom Consumption: Experimental Evidence in a Rat Model In rats, very high doses of chaga powder caused kidney injury with oxalate crystals; this is animal data, not a human dose.
- Isolation and characterization of a novel platelet aggregation inhibitory peptide from the medicinal mushroom, Inonotus obliquus A lab and mouse study found a chaga mycelium extract and a peptide from it reduced platelet clumping; no person took part.
- Inonotus obliquus - from folk medicine to clinical use A 2020 review of chaga research says the evidence is mostly cell and animal work and that properly designed human studies are still needed.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.