Chaga Benefits Evidence: What Studies Show and Side Effects

Chaga is a fungus that grows on birch trees in cold climates, and most people drink it as a tea because of its bitter taste. Memorial Sloan Kettering’s chaga page says the safety and efficacy of chaga have yet to be evaluated in clinical studies, and there is no human systematic review or randomized trial of chaga. What exists is lab and animal research, which points to possible effects on immunity, inflammation and blood sugar, but none of those effects has been shown in people.

What is birch tree fungus tea?

Birch tree fungus tea is chaga tea. Chaga (Inonotus obliquus) is the fungus MSK describes as commonly found on birch trees in cold climates. The medicinal part is the conk, which is made of wood from the host tree and mycelium of the fungus. MSK says chaga is edible, but most people drink it as a tea made from the whole mushroom. It is also sold as tablets, capsules and powders. You may also see it called cinder conk, birch conk, clinker polypore or Bai Hua Rang.

Chaga at a glance

What the evidence shows for each use

The findings below come from lab dishes and animals. MSK’s named uses come first.

Immune system and allergy (mouse and cell studies)

MSK lists boosting the immune system as a use people give chaga. It attributes immune effects to chaga’s influence on Th1/Th2 cytokines and on antibody production. Two mouse studies it cites found chaga extract reduced IgE production. One was by Ko and colleagues (2011) in ovalbumin-sensitized mice. The other was by Yoon and colleagues (2013) in mice with anaphylactic shock.

Inflammation (mouse colitis and lab work)

MSK lists reducing inflammation as a use. In mice with colitis induced by dextran sulfate sodium, an aqueous extract lowered TNF-alpha, iNOS and IL-1beta, according to Mishra and colleagues (2012). MSK says chaga’s anti-inflammatory and pain-relieving properties may occur via inhibition of iNOS and COX-2, a mechanism it reports from lab work.

Blood sugar (lab work and diabetic mice)

MSK says chaga may have antidiabetic effects. It cites a study of dry matter from a culture of the fungus in normal and alloxan-diabetic mice, by Sun and colleagues (2008). It also cites a study of chaga polysaccharides in mice with streptozotocin-induced diabetes, by Wang and colleagues (2017). In lab tests, terpenoids from chaga inhibited alpha-glucosidase, an enzyme involved in breaking down sugars. Chaga also had additive effects in lowering blood sugar in vitro.

Liver (cell work and a review)

MSK lists liver protection, or hepatoprotection, among purported uses. The research it cites on the liver is in cells. Aqueous extracts inhibited the growth of human liver cancer (hepatoma) cells, according to Youn and colleagues (2008). That is a result on cancer cells, not on liver protection in people. A 2024 review in Mycology, indexed on PubMed, lists hepatoprotective activity among chaga’s properties. Its stated aim is to explore chaga as a naturally sourced option.

Cancer cells and tumors (lab and mouse work)

MSK says chaga has been used as a folk remedy in Russia and other northern European countries for various ailments, including cancer. The research it cites on cancer is in cells: colon, lung, liver and cervical cancer cells. MSK also reports that chaga inhibited melanoma in a mouse model. One study it cites found selective cell death in tumor cells, without affecting healthy cells.

Learning and memory (animal studies)

MSK reports that in animal studies, a methanolic extract of chaga had beneficial effects on learning and memory. The extract lowered markers of oxidative stress and acetylcholinesterase activity, and restored glutathione, superoxide dismutase and acetylcholine levels. One study MSK cites, by Giridharan and colleagues (2011), tested this against scopolamine-induced cognitive dysfunction.

Endurance and fatigue (mouse study)

MSK says oral polysaccharides from chaga increased endurance in mice. The mice also had higher glycogen in the liver and muscle, and lower blood lactic acid and serum urea nitrogen. The study is Yue and colleagues (2015).

Viral infection (lab work)

MSK lists antiviral activity. The study it cites, by Pan and colleagues (2013), found an aqueous extract prevented herpes simplex virus from entering cells. It did this by inhibiting virus-induced membrane fusion, in lab tests.

Oxidative DNA damage in patient cells (lab work)

MSK’s reference list includes a study by Najafzadeh and colleagues (2007). Its title says a chaga mushroom extract inhibited oxidative DNA damage in lymphocytes from patients with inflammatory bowel disease. This is the finding on MSK’s list closest to people, and it is still lab work on cells.

Doses used in studies

The amounts that appear in the kidney reports are what people took, not doses chosen by researchers, and they are not amounts to copy. In the first case, a 72-year-old woman with liver cancer took 4 to 5 teaspoons of chaga powder daily for six months. In the second, a 69-year-old man took 10 to 15 grams of chaga powder a day along with 500 mg of vitamin C a day, for three months. Our vitamin c benefits evidence page covers that vitamin’s human studies, doses and safety.

Side effects, safety and medicine interactions

MSK’s consumer section says there aren’t any reports of side effects from using chaga mushroom. Its adverse-reaction section, however, lists three kidney cases.

MSK names oxalic acid among the compounds identified in chaga extracts. The first two cases are labelled oxalate nephropathy, a kidney injury.

Is it safe to take chaga every day?

MSK says it is generally safe to eat chaga mushroom and drink it as a tea. The kidney cases involved daily powder for months, and the third involved long-term use. Talk with your healthcare provider before taking chaga supplements, since MSK notes that herbal supplements are stronger than the herbs you would use in cooking.

Is chaga hard on your liver?

MSK does not report liver harm from chaga. Its reported harm is to the kidneys. Its liver findings are lab results, described above.

What not to mix with chaga?

Who should talk to a clinician first?

MSK advises telling your healthcare providers about any supplements you take, and talking with them before taking chaga supplements. Talk with a clinician first if you:

• take warfarin or another blood thinner, or any antiplatelet or anticoagulant drug
• take medicine for diabetes or blood sugar
• have kidney disease or a history of kidney problems, given the kidney cases above
• take any prescribed medicine, and want to know whether a supplement fits with it

What is still unknown

• Whether chaga does anything in people. Every use above rests on lab or animal work. There is no human trial to read for any of them.
• The right amount. Ask the company what amount is in each serving.
• Study size and length. Check the original studies for group sizes and how long they ran.
• Does chaga keep you up? If a product is a blend, check the label for caffeine or other stimulant ingredients.
• Is chaga psychoactive? Its brain findings are animal studies of learning and memory.
• Is chaga better than Lion’s Mane? Ask a clinician which fits your situation.

How to read a label that lists chaga

Supplements come as tablets, capsules and powders, and MSK notes that herbal supplements are stronger than the herbs you would use in cooking. Use this checklist when you read a label.

For more on judging a label’s claims, read our ingredient evidence vs marketing claims guide.

By ClinicalStudyConnect.com Research Desk

This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.