Chaga (Inonotus obliquus) is a fungus that grows primarily on birch trees in cold northern climates, including Russia, Siberia, northern Europe, and parts of Canada. Used for centuries in traditional Siberian and Northern European folk medicine, it has attracted increasing scientific attention in recent decades. Among the areas of emerging interest is its potential relationship with blood glucose regulation. While much of this research remains at the preclinical stage, the findings are notable enough to warrant a clear-eyed review of what the evidence currently shows.
What Is Chaga and What Does It Contain?
Chaga is not a conventional mushroom in appearance: it presents as a dark, woody mass on the outside of birch bark, with an inner core that is orange-brown in color. It contains a range of bioactive compounds, including polysaccharides, betulinic acid (derived from the birch host), inotodiol, lanostane-type triterpenoids, and melanin-rich pigments. Its polysaccharide fraction, in particular, has been the subject of most metabolic research.
The diversity of compounds in chaga makes it analytically complex. Different preparations: water extracts, alcohol extracts, or whole-ground preparations, yield different compound profiles, and this variability has implications for interpreting and comparing studies. For more context on how extraction methods affect supplement composition, see our guide on Chaga Mushroom and Antioxidants: How It Compares to Other Superfoods.
Preclinical Evidence on Blood Glucose
The bulk of research on chaga and blood sugar has been conducted in animal models, primarily rodents induced with type 2 diabetes or high-fat diet conditions. These studies offer mechanistic insights, though they cannot be directly extrapolated to human outcomes.
One 2024 study published in the Chinese Journal of Natural Medicines examined chaga extract in a high-fat diet and streptozotocin (HFD/STZ) mouse model, a common approach for inducing glucolipid metabolism disorders. The researchers found that chaga administration was associated with improved glucolipid metabolism markers and renal function indicators, with effects linked to modulation of the NOS-cGMP-PDE5 signaling pathway.[1] The study notes that prior investigations from the same group had already established hypoglycemic effects of chaga in similar models.
A 2025 study in the Journal of Ethnopharmacology investigated betulinic acid, a triterpenoid compound isolated from Inonotus obliquus, in db/db mice, a well-characterized model of type 2 diabetes. The researchers found that betulinic acid administration was associated with improvements in multiple metabolic parameters, including modulation of short-chain fatty acid-producing gut bacteria and alterations in amino acid metabolism pathways linked to insulin sensitivity.[2] These findings suggest that the metabolic effects of chaga compounds may operate partly through the gut-liver axis, though this mechanism requires further validation in human subjects.
A separate 2025 study, also published in the Journal of Ethnopharmacology, focused specifically on chaga polysaccharides and their effects on lipid-induced skeletal muscle insulin resistance. The study found that the polysaccharide fraction appeared to ameliorate insulin resistance markers via PI3K/AKT and AMPK/ACC1/CPT1 signaling pathways, both of which play recognized roles in glucose uptake and fatty acid oxidation in muscle tissue.[3] The authors proposed that polysaccharides from chaga may represent a candidate for further investigation in metabolic conditions.
The Role of Polysaccharides and Betulinic Acid
The two primary compound classes implicated in chaga’s potential metabolic effects are polysaccharides and betulinic acid. These operate through distinct mechanisms and are present in varying amounts depending on how the fungus is prepared.
Polysaccharides from medicinal mushrooms are well studied for their effects on immune modulation and, to a lesser extent, on glycemic markers. In chaga specifically, research suggests they may help sensitize cells to insulin signaling, though the relevant pathways are complex and not yet fully characterized in human physiology.
Betulinic acid originates not from chaga itself but from the birch bark that serves as the fungus’s substrate. Chaga absorbs and biotransforms this compound from its host tree, which is one reason chaga grown on non-birch substrates may have a fundamentally different biochemical profile. The metabolic effects of betulinic acid observed in animal models are promising, but human pharmacokinetic data remains limited.
Limitations of Current Evidence
It is important to be direct about what the current evidence does and does not show. As of mid-2026, there are no large-scale, randomized controlled trials in humans examining chaga’s effects on blood glucose or insulin sensitivity. The studies reviewed here are conducted in animal models, which do not always translate predictably to human outcomes.
Several additional caveats apply:
- Dose extrapolation: Animal doses used in these studies are not directly applicable to human supplementation. The amounts used in laboratory models are determined by body weight scaling and do not correspond to what is found in commercial supplements.
- Preparation variability: Water extracts, ethanolic extracts, and isolated fractions differ substantially in their compound composition. Studies using isolated betulinic acid, for instance, may not reflect outcomes from whole-mushroom products.
- Diabetes medications: Individuals managing blood sugar with pharmaceutical agents should be aware that any supplement with potential glucose-modulating effects may theoretically interact with their medication regimen. Consulting a healthcare provider is strongly advisable.
- Chaga and oxalates: Chaga contains unusually high levels of oxalic acid. There are documented cases in the literature of oxalate nephropathy associated with high-dose chaga consumption over extended periods. This is a relevant safety consideration independent of the blood sugar question.
What Early Studies Suggest: A Summary
Taken together, preclinical research suggests that chaga and its constituent compounds, particularly polysaccharides and betulinic acid, may have effects on glucose metabolism and insulin signaling pathways. These effects appear to operate through multiple mechanisms, including modulation of skeletal muscle insulin resistance, gut microbiome composition, and hepatic lipid metabolism.
Whether these findings will translate into clinically meaningful outcomes in humans is a question that current evidence cannot answer. Researchers have identified plausible mechanisms and consistent patterns in animal models, which may justify further human investigation. What they have not established is a defined therapeutic effect in human populations with or at risk for metabolic disorders.
For individuals with diabetes or prediabetes, chaga remains in the category of “areas of interest” rather than evidence-based interventions. A physician or registered dietitian is the appropriate source of guidance on any supplement that may affect blood glucose, especially where pharmaceutical management is already in place.
References
- [1] Feng Y, Liu J, Gong L, et al. Inonotus obliquus (Chaga) against HFD/STZ-induced glucolipid metabolism disorders and abnormal renal functions by regulating NOS-cGMP-PDE5 signaling pathway. Chin J Nat Med. 2024;22(7):619-631. https://pubmed.ncbi.nlm.nih.gov/39059831/
- [2] Lin B, Bai G, Zhang Y, et al. Betulinic acid from Inonotus obliquus ameliorates T2DM by modulating short-chain fatty acids producing bacteria and amino acids metabolism in db/db mice. J Ethnopharmacol. 2025;342:119417. https://pubmed.ncbi.nlm.nih.gov/39884483/
- [3] Guo Y, Xu N, Meng Q, et al. Mechanisms of Inonotus obliquus (Fr.) Pilát polysaccharides in ameliorating lipid-induced skeletal muscle insulin resistance via PI3K/AKT and AMPK/ACC1/CPT1 signaling pathways. J Ethnopharmacol. 2025;349:119938. https://pubmed.ncbi.nlm.nih.gov/40348308/
This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting any supplement.
