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Inonotus obliquus, commonly known as Chaga mushroom (a Latinisation of the Russian term ‘чага’), is a fungus in Hymenochaetaceae family. It is parasitic on Birch and other trees. The sterile conk is irregularly formed and has the appearance of burnt charcoal. It is not the fruit body of the fungus, but a big mass of mycelium, mostly black due to the presence of massive amounts of melanin. The fertile fruit body can be found very rarely as a resupinate (crustose) fungus on or near the clinker, usually appearing after the host tree is dead. I. obliquus grows in birch forests of Russia, Korea, Eastern and Northern Europe, Northern areas of the United States, in the North Carolina mountains and in Canada. The Chaga mushroom is considered a medicinal mushroom that has a place in Russian and Eastern European folk medicine.


The name Chaga comes from the Russian word of the mushroom (anglicized from Czaga), which in turn is purportedly derived from the word for the fungus in Komi-Permyak, the language of the indigenous peoples in the Kama River Basin, west of the Ural Mountains. It is also known as the Clinker Polypore, Cinder Conk, Black Mass and Birch Canker Polypore.[2]

In Norwegian the name is kreftkjuke which literally translates as cancer polypore, referring to the fungus’ appearance or to its alleged medicinal properties.

In England and Canada it is known as the Sterile Conk Trunk Rot of Birch,, which refers to the growth of the fruiting bodies, which grow under the outer layers of wood surrounding the sterile conk once the tree is dead, in order to spread the spores. In France it is called the Carie Blanche Spongieuse de Bouleau (spongy white birch tree rot) and in Germany it is known as the Slate Inonotus (Schiefer Schillerporling). The Dutch name is Berkenweerschijnzwam (birch mushroom glow).

It has also been known by other Latin names, such as Polyporus obliquus and Poria obliqua.[2]

Medicinal use

Since the 16th century, there are records of chaga mushroom being used in folk medicine and the botanical medicine of the Eastern European countries as a remedy for cancer, gastritis, ulcers, and tuberculosis of the bones. A review from 2010, stated, “As early as in the sixteenth century, Chaga was used as an effective folk medicine in Russia and Northern Europe to treat several human malicious tumors and other diseases in the absence of any unacceptable toxic side effects. Chemical investigations show that I. obliquus produces a diverse range of secondary metabolites including phenolic compounds, melanins, and lanostane-type triterpenoids. Among these are the active components for antioxidant, antitumoral, and antiviral activities and for improving human immunity against infection of pathogenic microbes. Geographically, however, this fungus is restricted to very cold habitats and grows very slowly, suggesting that Chaga is not a reliable source of these bioactive compounds. Attempts for culturing this fungus axenically all resulted in a reduced production of bioactive metabolites.”[3] Cultivated Chaga results in a product with a very different composition of active components, in particular the phyto-sterols. Betulinic acid is absent because cultivation is not using birches, the supplier of the betulin content in Chaga.[4] In 1958, scientific studies in Finland and Russia found Chaga provided an epochal effect in breast cancer, liver cancer, uterine cancer, and gastric cancer, as well as in hypertension and diabetes.[5] In 1973 in interesting case study including 50 patients about the effect of a Chaga extract on psoriasis was published in the Russian journal Vestnik Dermatologii i Venerologii. The outcome was almost 100% successful.[6]

In China, Japan and South-Korea hot water extracts of the non-linear, complex (1<-3) and (1<-6) ß-glucan polysaccharides that are found in Chaga and other mushrooms from the family Hymenochaetaceae are being produced, sold and exported as anti-cancer medicinal supplements. The biologic properties of crude preparations of these specific β-glucans have been studied since the 1960s. Although these molecules exhibit a wide range of biologic functions, including anti tumor activity, their ability to prevent a range of experimental infectious diseases has been studied in the greatest detail.[7] Recent scientific research in Japan and China has been focused more on the anti-cancer potential and showed the effects of these specific polysaccharides to be comparable to chemo therapy and radiation, but without the side effects.[8][9] Further research indicated these polysaccharides have strong anti-inflammatory[10] and immune balancing properties,[11] stimulating the body to produce NK (natural killer) cells to battle infections and tumor growth, instead of showing a direct toxicity against pathogens. This property makes polysaccharide-based supplements stand out from standard pharmaceuticals – no side effects will occur / develop; the body is healing itself.[12] Herbalist David Winston maintains that it is the strongest anti-cancer medicinal mushroom. Russian Literature Nobel Prize laureate Alexandr Solzhenitsyn wrote two pages on the medicinal use and value of chaga in his autobiographical novel, based on his experiences in a hospital in Tashkent, “Cancer Ward” (1968).

Betulin and betulinic acid, are compounds found naturally in chaga and birch trees. The compounds are now being studied for use as a chemotherapeutic agent. Whereas Betulin as it is found in birch bark is indigestible by humans, the Chaga mushroom converts it into a form that can be digested orally. In an animal study, researchers found betulin from birch bark lowered cholesterol, obesity and improved insulin resistance.[13]

Although the majority of research has been performed in vivo and in vitro, there have been a few human clinical trials. In a 48 patient human clinical trial in Poland in 1957, ten patients treated with chaga showed a reduction of tumor size, a decrease in pain, a decrease in the intensity and the frequency of hemorrhaging, and a recovery that was accompanied with better sleep, appetite and feelings of improvement. Most of these patients were females treated with chaga for cancer of the genital organs or breast cancer.[14]


Chaga is usually grated into a fine powder and used to brew a beverage resembling coffee. For medicinal use, an extraction process is needed to release the major active ingredients, the polysaccharides[15]—which are found in the mostly indigestible chitin cellwalls of the Chaga. Humans lack the enzyme chitinase and therefore cannot fully digest raw mushrooms or derivatives of these. Scientific studies and research are in general also based on highly concentrated extracts. Currently three extraction processes are used, each with a different outcome.

  • Hot water extraction. This is the most common and cheapest way. All water soluble components will be present in the resulting extract. Non-water soluble components, like phyto-sterols, betulinic acid and betulin, will be absent. Several extraction rounds can result in very high levels of polysaccharides, up to 50%. Polyphenolic components are also present.[citation needed]
  • Alcohol / ethanol extraction. This will isolate the non-water soluble components, like betulinic acid, betulin and phyto-sterols.
  • Fermentation method. Being the most time consuming and therefore the most expensive (to purchase), this method is not used very often. Because fermentation methods are not standardized (many types of bacteria and fungi can be used in the process) the outcome is also not standardized.

Extracts with a therapeutic value usually combine two methods, in general hot water extraction and alcohol / ethanol extraction. This will result in the most valuable components being present. Cheap mass produced extracts are in general hot water based low percentage (4-20%) polysaccharide extracts with limited therapeutic value. The information on the label will usually reveal a lot, be it by inclusion or exclusion of components.


In 1998 there was a study in Poland that demonstrated Chaga’s inhibiting effects on tumor growth.[16] Noda and colleagues found that betulin seems to work highly selectively on tumor cells because the interior pH of tumor tissues is generally lower than that of normal tissues, and betulinic acid is only active at those lower levels. Fulda et al. found in 1997 that once inside the cells, betulinic acid induces apoptosis (programmed cell death) in the tumors.[citation needed] In 2005, I. obliquus was evaluated for its potential for protecting against oxidative damage to DNA in a human keratinocyte cell line. The study found that the polyphenolic extract protected these cells against hydrogen peroxide-induced oxidative stress.[17] Another study that year found the endo-polysaccharide of Chaga produced indirect anti-cancer effects via immuno-stimulation. The mycelial endo-polysaccharide of I. obliquus was identified as a candidate for use as an immune response modifier and indicate that the anti-cancer effect of endo-polysaccharide is not directly tumorcidal but rather is immuno-stimulating.[18][12] It also has anti-inflammatory properties.[11] Saitoh Akiko published on the antimutagenic effects of Chaga in 1996. Mizuno et al. published on the anti-tumor and hypoglycemic activities of the polysaccharides from the sclerotia and mycelia of Chaga.[19] Due to the hypoglycemic activity of polysaccharides caution may be taken by those with hypoglycemia.

Written on February 10th, 2012 , Botany, Mycology Tags:

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