Chaga mushroom supplement: what is known and the kidney risk to understand
We research products from makers' specs and health sources; we do not run hands-on tests. Links to Amazon may earn us a commission at no cost to you. How this works.
- Chaga tea chunks or tea bags. Best for: People who want chaga the traditional way. See options on Amazon
- Organic chaga capsules. Best for: Adults whose doctor has cleared them for chaga. See options on Amazon
What chaga is
MSK describes chaga as a fungus commonly found on birch trees in cold climates, used as a folk remedy in Russia and other northern European countries. The part used medicinally, called a conk, is a mix of birch wood and fungal mycelium. Because it tastes bitter, most people drink it as a tea rather than eating it.
A 2024 review in Mycology says chaga has been used since the sixteenth century, with folk records for digestive cancers, diabetes, infections and liver disease. Its compounds include polysaccharides, triterpenoids, polyphenols and lignin metabolites. The review summarizes research on anti-inflammatory, antioxidant, anti-diabetic, anti-obesity, liver-protective and anti-fatigue activity, mostly from lab and animal work.
MSK also notes wild chaga reserves have nearly been exhausted, so researchers are developing cultivated substitutes.
What the research shows
| Claim | What the evidence says |
|---|---|
| Immune support | Lab and animal studies only |
| Inflammation and pain | Lab and animal studies only |
| Blood sugar | Lab and animal studies only |
| Cancer | Lab and animal studies only |
| Safety and effectiveness in people | Not yet evaluated in clinical studies (MSK) |
MSK lists preclinical findings including antitumor, antiviral, antiplatelet, antidiabetic, antioxidant, pain-relieving and immune effects, and better exercise endurance in animals given chaga polysaccharides. Chaga extracts also killed colon, lung and liver cancer cells in the lab.
But MSK states plainly that chaga's safety and efficacy have yet to be evaluated in clinical studies. Marketing claims about immunity, inflammation or cancer are not backed by human trials.
The kidney risk: oxalate
Chaga contains a lot of oxalate, a compound that can form crystals in the kidneys. MSK and a 2020 case report in the Journal of Korean Medical Science describe serious kidney injury:
- A 72-year-old woman with liver cancer took 4 to 5 teaspoons of chaga powder daily for 6 months, developed oxalate kidney damage and needed dialysis; her kidney function did not recover.
- A 69-year-old man took 10 to 15 grams of chaga powder plus 500 mg of vitamin C daily for 3 months; his kidney function improved after dialysis and steroids.
- A 49-year-old man took chaga powder long term for eczema and developed end-stage kidney disease. Testing showed his chaga had extremely high oxalate content, and his estimated daily oxalate intake was several times higher than a usual diet.
The case report authors call chaga a potential risk factor for chronic kidney disease. Avoid chaga supplements if you have kidney disease, and do not take large amounts for long periods.
Other cautions
- Blood thinners. Chaga reduced platelet clumping in animals and may add to anticoagulant or antiplatelet drugs. MSK says to talk with your provider if you take warfarin.
- Diabetes medicines. In lab studies chaga had additive blood sugar lowering effects; ask your doctor if you take diabetes medicine.
- Food vs supplements. MSK says eating chaga or drinking it as tea is generally safe, but supplements are stronger than amounts used as food.
- Pregnancy and nursing. Ask your provider before using chaga supplements.
How to choose, if you use chaga
- Talk with your doctor first, especially about kidney health and blood thinners.
- Modest amounts. The kidney cases involved large amounts of powder taken daily for months. Follow labels and avoid stacking several chaga products.
- Tea is the traditional form. MSK notes chaga is usually consumed as tea.
- Single ingredient and tested. Prefer clearly labeled chaga with third-party testing. Mushroom blends add other ingredients.
- Source. Labels may say wild-harvested or cultivated; MSK notes wild supplies are under pressure.
What to look for when you buy
Chaga tea chunks or tea bags
Best for: People who want chaga the traditional way
MSK notes chaga is usually brewed as tea and that drinking it as tea is generally safe.
Watch out: Still contains oxalate. Avoid with kidney disease, and do not drink large amounts daily for months.
See options on AmazonOrganic chaga capsules
Best for: Adults whose doctor has cleared them for chaga
Single-ingredient capsules make the daily amount clear and easy to keep modest.
Watch out: Serious oxalate kidney injury has been reported with long-term powder use. Not with blood thinners without your doctor's okay.
See options on AmazonQuestions people ask
- What is chaga good for?
- Lab and animal studies suggest many effects, but MSK says its safety and effectiveness have not been evaluated in clinical studies.
- Is chaga bad for your kidneys?
- It can be. Chaga is very high in oxalate, and case reports describe serious oxalate kidney injury after months of chaga powder.
- Can I take chaga with blood thinners?
- Ask your doctor first. Chaga reduced platelet clumping in animal studies and may raise bleeding risk.
- Is chaga tea safe?
- MSK says drinking chaga as a tea is generally safe, but avoid large amounts if you have kidney problems.
- Where does chaga come from?
- It grows on birch trees in cold climates and has long been used as a folk remedy in Russia and northern Europe.
Sources
- Chaga Mushroom: About Herbs (mskcc.org), Memorial Sloan Kettering Cancer Center
- Therapeutic properties of Inonotus obliquus (Chaga mushroom): A review (pmc.ncbi.nlm.nih.gov), Mycology (PMC11132974)
- Development of End Stage Renal Disease after Long-Term Ingestion of Chaga Mushroom: Case Report and Review of Literature (pmc.ncbi.nlm.nih.gov), Journal of Korean Medical Science (PMC7234858)