With its charcoal-like appearance, Chaga is a fungus that grows primarily on the trunks of birch trees. Once Chaga infects a tree trunk, it can grow there for up to 80 years. The mushroom has been used for centuries and is often touted as a cure-all within the realm of alternative medicine: from gastrointestinal diseases to cancer, there are few ailments for which Chaga has not been used as a potential remedy.
Chaga contains a wide variety of potentially beneficial chemical compounds, such as polyphenols, melanin, triterpenoids, and polysaccharides. Among these, polysaccharides are the most well researched.
There are in vitro and animal studies reporting that Chaga may benefit health. For example, an animal study showed Chaga has antioxidant properties and could positively affect the gut microbiota in mice with chronic pancreatitis. Additionally, there is some in vitro evidence that Chaga has potential anti-cancer effects.
To date, the only study on the effects of Chaga in humans is a case series (a study that looks at a group of people receiving the same treatment) from 1973. In this study, 50 people with both gastrointestinal disease and psoriasis either consumed Chaga orally (1 tablespoon, 3 times per day) or topically (the dosage and duration was not reported). The primary outcome was the improvement in patient’s psoriasis lesions. 38 participants were considered completely cured, 8 participants showed improvement, and 4 participants showed no effect. Considering the age of the study, lack of control group, no randomization, and no standardized measurement of psoriasis disease progression, more human research is needed to determine the utility of Chaga.
The safety data for Chaga is limited. The main concern is that it contains high levels of oxalate (a compound commonly found in plants that can cause kidney stones). While anecdotal evidence suggests it is relatively safe, there are two case reports of oxalate-induced kidney disease (a condition that occurs due to the buildup of calcium-oxalate crystals within the kidney) after long-term consumption of Chaga. One case study found that a 49-year-old man with no other diseases developed end-stage renal disease after consuming Chaga daily for 5 years. However, he had also consumed more than double the recommended manufacturer dose. Another case study reported that a 72-year-old woman with liver cancer developed oxalate-induced kidney disease after 6 months of consuming 4–5 teaspoons of Chaga daily. It is believed that the high oxalate content of Chaga — one study found there are 6.72–97.59 milligrams (mg) of oxalate per gram of Chaga — caused kidney disease in these two cases.
No. Although Chaga is a mushroom, it doesn’t have any psychoactive compounds.
Given there are few human studies using Chaga, it is difficult to determine its safety for pregnant or breastfeeding women. As such, it is not recommended to consume Chaga while pregnant or breastfeeding unless directed by a healthcare provider.
Unfortunately, there are no human studies directly investigating the side effects of Chaga.
There is some lab-based evidence that Chaga may have similar mechanisms of action (the way a substance produces an effect) to blood thinners and diabetic medications. Therefore, it is best to consult your healthcare provider before supplementing with Chaga.
Supplementing with high doses of vitamin C (>1,000 mg/day) can increase the excretion of oxalates from the kidneys. This could increase the risk of kidney stones or kidney disease. Several case studies have reported oxalate-induced kidney disease due to vitamin C supplementation.  It’s important to note that in all of these cases of kidney disease, people were supplementing with doses ranging from 480–5,000 mg, which would suggest that the dose of vitamin C needed to cause kidney disease would differ from person to person.