Written by Matthew Clark
Medicinal fungi like chaga have boomed in popularity in recent years. This article shares some of the potential ways it can support our health.
Chaga (Inonotus obliquus) is a black, parasitic mushroom, which looks on the outside like a lump of burnt, craggy charcoal; it belongs to the Hymenochaetacea family of fungi. The genus Inonotus is widespread is widespread in North America, Asia and Europe and comprises around 100 species, represented in Europe by four species, one of which is Inonotus obliquus.
The term ‘chaga’ most probably derives from Russian; chaga is also known as birch conk (a woody growth), clinker polypore, cinder conk and black mass, and may usually be found on the boles of birch trees, (1) though occasionally on other trees: on alder, ash, beech, chestnut, hornbeam, plane-tree, poplar, maple, rowan, oak, walnut, and willow. However, reports on the growth of chaga on trees besides beech are often unreliable as the fungus growing on the other kinds of tree are similar and often confused with chaga. (2)
Chaga grows externally on the bark of the host tree, be it living, dead, standing or fallen. Under the black surface, the chaga mycelium is an orange/brown colour. It causes the decomposition of live boles and usually grows to around between 25-40 centimetres; it dries to a consistency similar to that of hard cork. Chaga usually infects trees that are 30-40 years old through wounds in the bark and can continue to grow on the bole for another 30-80 years. On old trees the growth of chaga can exceed 50 cm in diameter. (3)
Low in calories, high in fibre, and rich in minerals and vitamins, chaga has been used as a traditional medicine in various cultures since time immemorial, particularly in Russia, China, Poland (4) and the Baltic countries. It is also used for food in China. (5) Chaga is used to treat diabetes, parasites, tuberculosis, inflammation, gastro-intestinal problems, heart disease and several kinds of cancer. (6) Perhaps the oldest reference to the use of chaga as a medicine is by Hippocrates (c. 460–370 BCE) in his Corpus Hippocraticum, in which is described the use of infusions of chaga to wash wounds. (7)
For medicinal treatments chaga is usually ground to a fine powder and made into a tea, which tastes like mushrooms. It is also available in capsule form as a supplement, sometimes in combination with other mushrooms, such as cordyceps. However, many commercial products are simply unprocessed powdered chaga without having been extracted. This means the active compounds are not bioavailable and so one must be careful when buying a product that the quality is good and that the preparation process is clearly explained if it is simply a powder and not an extract.
The chaga mushroom has been the subject of many scientific investigations to explore its medicinal properties, particularly by researchers in South Korea. (8) Chaga has been shown to be effective in reducing cancerous tumours, thereby suppressing the progression of cancer, through promoting energy metabolism. (9) In the semi-autobiographical novel Cancer Ward by Aleksandr Solzhenitsyn, set in Russia and first published in 1968, cancer patients are prescribed chaga tea.
Several studies on mice and on human cells in vitro have demonstrated the effectiveness of chaga as an anti-tumour agent, effective in the treatment of several kinds of cancers, including cancer in the colon, (10) liver, (11) prostate, breast, (12) lung, stomach, and cervix. (13)
Compounds known as triterpenes/triterpenoids have been extracted from chaga and found to be effective in killing breast cancer cells. (14)
The chaga fungus contains inotodiol (a lanostane triterpenoid), which has anti-tumour properties. (15) Inotodiol and betulin (another triterpenoid with a lupane structure) are found almost exclusively in the fungus growing on birch trees. (16) Betulin forms up to 30% of the dry weight of silver birch bark; it is found in large amounts in chaga and has anti-cancer properties. (17) It is currently believed that the anti-cancer potential of the mushroom is primarily due to the high content of polysaccharides (18) in the mushroom. (19)
The immune system
Chaga has the full spectrum of immune-stimulating phytochemicals found in other mushrooms, such as in maitake and shitake, (21) which are widely consumedin Japan. It has been found that the compounds in mushrooms in general that inhibit tumour growth do so mostly by stimulating the immune system. (22) Chaga may be useful as an immune enhancer in people with either suppressed or compromised immune systems, who may develop auto-immune diseases such as psoriasis, rheumatoid arthritis or type 1 (auto-immune) diabetes. Chaga is a potent immune modulator and could also be used to treat people whose bone marrow has been damaged by chemotherapy. (23)
Many studies have confirmed chaga’s anti-inflammatory properties. (23) One study (24) concluded that chaga could be useful to treat inflammation, notably in bowel disease. It has now evident that inflammation is implicated in numerous health issues, including anxiety, unipolar and bipolar depression, schizophrenia, post-traumatic stress disorder, asthma, rheumatoid arthritis, cardiovascular disease, obesity, diabetes, osteoporosis, Alzheimer’s disease, certain cancers and stroke.
Eight out of ten of the leading causes of death in the USA involve inflammation. (25) More research is needed for specific inflammatory processes and conditions, however it would be a viable investigation route to see how chaga can effect illnesses where inflammation is involved.
Besides being anti-inflammatory, chaga is also rich in anti-oxidants, (26) the main anti-oxidants being polyphenols and triterpenoids. As noted above, triterpenoids are effective against some forms of cancer. Antioxidants can prevent or reverse damage to cells caused by aging, the environment or lifestyle.
Polyphenols can help manage both blood pressure and blood sugar levels, and reduce chronic inflammation. There are around 8,000 kinds of polyphenols, which are in many kinds of foods in greater or lesser quantities. Some of the commonly consumed polyphenols include flavonoids, such as quercetin and catechins, which are in fruits; capsaicinoids, in chili peppers; lignans and stilbenes, in vegetables and whole grains; resveratrol in red wine; and ellagic acid in berries. High levels of anti-oxidants are in chokeberries, elderberries and blueberries. (27) However, several surveys indicate that the highest levels, by far, of anti-oxidants in plant sources are in chaga. (28)
Chaga is particularly rich in the antioxidant known as superoxide dismutase (SOD), which has been shown to reduce free radical damage, preventing wrinkles and having an anti-cancer effect. (29) Several extracts from chaga, including polysaccharides, have also been shown to have neuroprotective effects in degenerative diseases such as Alzheimer’s and Parkinson’s. (30)
Studies on the effect of particular compounds in chaga have indicated that after four weeks they can significantly reduce the body weight, blood glucose levels, and plasma insulin levels of mice with diabetes. (31) It has been shown that the polysaccharides in chaga have hypoglycaemic activity, reducing blood sugar levels.(32) Other studies, (33) also on rats and mice, confirm that chaga is antioxidant, can reduce blood sugar, and provided further indications that chaga would most probably be effective against diabetes in humans.
Anti-bacterial, anti-parasitic, anti-viral
Two studies suggest the anti-bacterial and probiotic effect of chaga; another study indicates the anti-parasitic properties of polysaccharides in extracts from chaga. (34) The betulin in chaga can easily be converted to betulinic acid, which has been shown to have antiviral activity against HIV and malaria. (35) Polysaccharides extracted from chaga have been shown to be effective against other viral infections, including herpes, feline influenza (and other feline viral infections), and hepatitis C. (36)
It has been found that chaga modulates immune responses through secretion of cytokines in immune cells, and regulates antigen-specific antibody production. Chaga can increase serum levels of chemoprotective cytokines, (37) which are proteins that regulate the immune system and stimulate white blood cells, which protect against harmful bacteria and viruses.
Cytokines are also implicated in SARS-Covid infection, which causes illness through a cytokine ‘storm’. The triterpenoid inotodiol found in chaga, mentioned above, has been found to induce the proliferation of T-cells, which act against viral infection. (38) So, it may be that chaga can protect against the SARS-Covid virus.
Besides its other effects, chaga has also been shown to be able to reduce levels of total cholesterol in rats, (39) high levels of some forms of cholesterol being a factor in heart disease. It seems that it is the antioxidant effect of chaga that reduces cholesterol.
It has also been found that the polysaccharides in chaga increase in mice the production of sperm and testosterone, and ameliorate impaired reproductive function. (40)
The birch tree
Birch trees are native to northern latitudes of the world: to Russia, Siberia, northern Europe, Canada, Alaska, northern China and Korea. There are far more birch trees in Scotland than in England. The ancient Balts, Slavs and Finns regarded the birch as a sacred tree. In pre-Christian Ireland, birch was considered as one of seven sacred trees. (41) The name ‘birch’ derives from the Proto-Indo-European (PIE) root *bher∂g, which means ‘shine’/’brilliance’/’white’, reflected in names such as Albert, Herbert and Robert. (42)
The Celts saw in the birch the deity Brigit/Brigid, whose name derives from the same root, *bher∂g. Brigit was the muse of healers and bards in pre-Christian Ireland, where smitten boys would place fresh, green birch twigs in front of the house of the one they were courting. (43) Birch twigs used to be used in Europe for the beating of bounds and the flogging of delinquents – and formerly lunatics – to expel evil spirits. In Scandinavia the first leaves of birch mark the beginning of the agricultural year. The witches’ broom used to be made from birch and ash. (44)
In India, the birch tree is called bhūrja in Sanskrit. In north India, texts used to be inscribed on birch bark, which is used by North American Ojibwa Indians for many other purposes, such as for tools, mats, canoes and baskets. (45) The sap of birch trees is used to make a sugar substitute, known as xylitol. Birch sap has less sugar than maple and is used as a syrup by Lithuanians. (46)
In herbal medicine the sap of birch is believed to stimulate urine and bile, purify the blood, and strengthen the urinary tract. (47) Tea made from the leaves of white birch is used for dissolving kidney stones and as a laxative. Twigs and leaves are added to bath water as a treatment for itchy skin and hair loss, while the inner bark is simmered for fever. (48)
In the last couple of decades, numerous scientific studies have indicated the potential for chaga to treat several common diseases, including cancer and diabetes, as an immune-system booster, as an antioxidant, and against harmful viruses. Although the scientific tests so far have been almost exclusively conducted on rats and mice, and many of these studies lack in-depth experiments, (49) it seems highly likely that such effects would be replicated at least to some degree in humans. It should, however, be cautioned that chaga can prevent blood clotting, (50) so it should not be used by anyone using blood-thinning medication.
As mentioned above, the birch tree is revered in several cultures, notably by the Balts, Slavs and Finns. It has been suggested by some commentators (51) that this reverence for the birch tree may derive from the fact that one of the main places where the red, spotted, fly-agaric mushroom (Amanita muscaria) may be found is beneath birch trees. Fly-agaric has psychedelic effects and is used for shamanic purposes in some cultures in Siberia and North America. (52) It was famously, though incorrectly, (53) identified in the late 1960s by R. Gordon Wasson – one of the great mycologists of the 20th century – as the ‘nectar of immortality’, the ritual drink known as soma, (54) which is revered by the Brahmins of India. However, leaving this suggestion aside, perhaps, as a speculation, reverence for the birch tree has, instead, practical roots in the ancient use of chaga as a wondrous medicine.
- Betula fontinalis, Betula lenta, Betula lutea, Betula papyrifera, Betula pendula (silver birch), Betula pubescens/alba (white birch).
- Szychowski et al. (2021:293).
- Szychowski et al. (2021:293).
- Inonotus obliquus is a partially protected species in Poland (Szychowski 2021:293).
- Ma et al. (2013.
- Kim (2005).
- Szychowski et al. (2021:294).
- For a recent, comprehensive review of the scientific literature on research into the medical potential of chaga, see Szychowski (2021).
- Arata et al. (2016).
- Lee et al. (2015).
- Youn et al. (2008).
- Ma et al. (2013).
- Chung et al. (2010).
- Zhao et al. (2016).
- Chung et al. (2010).
- Phillips (2006:310). Betulin is also found in red alder (Alakurtti et al. 2006) and a few other plants (Moghaddam (2012).
- Alakurtti et al. (2006).
- Three important polysaccharides – starch, glycogen and cellulose – are composed of glucose.
- Szychowski et al. (2021:299).
- Kim (2005).
- Borchers et al. (2008:259).
- Kim (2005).
- Ma et al. (2013).
- Mishra et al. (2012).
- Slavich (2015).
- Cui et al. (2005); Liang et al. (2009).
- In one survey (WebMD 2020) it is reported that the foods with the highest levels of antioxidants are (per half-cup serving) chokeberries (1,123 mgs), elderberries (870 mgs), blueberries (535 mgs) and blackcurrants (485 mgs). Blackberries, raspberries and strawberries have around 160 mgs. Per ounce, cloves contain 542 mgs, and peppermint 427 mgs. Dark chocolate has 249 mgs per tablespoon (milk chocolate has just 35 mgs). Of all nuts, the most polyphenols are in chestnuts, with 347 mgs per ounce. Other sources of polyphenols include flax seeds (229 mgs per tablespoon); a small artichoke has around 260 mgs; a small red onion has around 170 mgs; an olive has around 20–25 mgs; and a cup of coffee has about 35 mgs of polyphenols.
- Acai berries reportedly contain 165 oxygen radical absorbent capacity (ORAC) units, pomegranates 105, and blueberries 24; chaga contains 1,104 (Chichaga 2015; Wild Kingdom 2022).
- Younus (2018).
- Szychowski et al. (2021: 295).
- Wang et al. (2017).
- Szychowski et al. (2021:299).
- Cha et al. (2006); Diao et al. (2014); Sun et al. (2015); Wang et al. (2017).
- Szychowski et al. (2021:296).
- Alakurtti et al. (2006); Moghaddam et al. (2012).
- Szychowski et al. (2021:294, 296).
- Kim (2005); Ko et al. (2011).
- Maza et al. (2021).
- Sun et al. (2015).
- Ding et al. (2020).
- Graves (1977:253).
- Online Etymological Dictionary (2022).
- Müller-Ebeling et al. (2003:8).
- Graves (1977:166, 173).
- Nyholm (2022).
- Chepaitis (2016).
- Müller-Ebeling et al. (2003:7).
- Hopman (1995:187).
- Szychowski et al. (2021:298).
- Hyun et al. (2006).
- For example: Müller-Ebeling et al. (2003:10).
- Morgan (1995:106–110).
- See Clark (2020).
- See Wasson (1969).