Also known as: Inonotus obliquus, Birch conk, Betulinic acid, Chaga mushroom
BotanicalEarly evidence
A dark fungal growth found on birch trees across northern forests. Popular in the mushroom category, though human evidence is thinner than for most, and its oxalate content is a genuine consideration nobody mentions.
Typical dose
1.0–3.0 g per day
Any time, with food; keep intake moderate
What it is
Chaga is a sterile conk of Inonotus obliquus, forming a black, cracked mass on the trunks of birch trees in cold northern regions. It is not a typical mushroom fruiting body but a mass of fungal and tree tissue, which is why its composition differs from other medicinal fungi.
Compounds of interest include beta-glucans, melanin, and betulinic acid and related triterpenes drawn from the birch host. It has traditional use across Siberia and Northern Europe, typically as a tea.
Sustainability is a real issue here in a way it is not for cultivated mushrooms. Chaga grows slowly, takes years to form, and is largely wild-harvested, with concerns about over-collection in accessible regions. Cultivated alternatives exist but differ in composition.
How it works
Beta-glucans interact with receptors on immune cells, the mechanism shared across medicinal fungi.
Chaga has notably high antioxidant activity in laboratory measures, largely attributed to its melanin and polyphenol content. Laboratory antioxidant capacity is a weak predictor of anything useful in a person, so this should be treated as a description of the material rather than a benefit.
Betulinic acid and related triterpenes drawn from the birch host have been studied for a range of activities in cell models. Human data on any of it is scarce.
What the evidence shows
Human trial evidence for chaga is very limited. The great majority of published work is laboratory or animal research, and there is little to draw on for what it does in a person taking it daily.
Its long traditional use across northern regions is worth acknowledging, but traditional use establishes acceptability rather than efficacy.
The honest position is that chaga is popular ahead of its evidence. It is a reasonable addition to a mushroom blend for variety, but anyone choosing it over better-studied options on the basis of the research is not reading the research.
Dosing
Common intake is 1-3 g daily of extract, though this is product convention rather than a researched dose.
As with all fungal products, judge on declared beta-glucan content and on whether the material is a genuine extract rather than milled raw conk, which is largely indigestible.
One caution worth taking seriously: chaga is very high in oxalate, considerably higher than most foods. Sustained high intake is not advisable, particularly if you have ever had kidney stones. Keep intake moderate, take breaks, and drink plenty of water alongside it.
At a glance
Common forms
Hot water extract, Dual-extracted powder, Raw milled conk, Chaga tea, Capsules
Half-life / duration
Not characterised in humans
Timing
Any time, with food; keep intake moderate
Competition status
Permitted — not on the WADA Prohibited List
Category
Botanical
Safety and side effects
Generally well tolerated at moderate intakes, with digestive upset the occasional complaint.
The oxalate content is the meaningful safety point and is specific to chaga rather than to mushrooms generally. There are documented reports of kidney problems following prolonged heavy chaga intake. Anyone who has had kidney stones, or who has been told their kidneys are not working normally, should avoid it.
Chaga also has immune-modulating activity, a mild effect on how readily blood clots, and may nudge blood sugar downward. Check with your doctor before use if you take regular medication.
Who should avoid it
Avoid if you have had kidney stones or have been told your kidneys are not working normally — chaga is unusually high in oxalate. Speak to your doctor before use if you take regular medication, particularly anything affecting blood clotting, or if your blood sugar or immune system is being managed. Avoid if sensitive to fungi or moulds. Not established for use in pregnancy or breastfeeding.
This entry is provided for information only. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Consult a qualified healthcare professional before use if you are pregnant, breastfeeding, taking medication or under medical supervision.
