One of the active constituents of Chaga is Vitamin D2 (Ergosterol). The best way for your body to absorb vitamin D is by getting between five and 30 minutes of sunshine at least twice a week, but if weather doesn’t permit, Vitamin D2 can reduce a vitamin D deficiency if taken regularly.
Chaga is also a natural BRM (Biological Response Modifier). It not only stimulates the body’s immune function when necessary, but can also slow it down when it’s overactive (in the case of allergies and many auto-immune diseases; e.g. lupus and psoriasis). In short, it will normalize the immune function, which classifies Chaga as an adaptogenic. The beta-glucans appear to be mainly responsible for that property, but many researchers believe it is actually the synergy between several, if not all constituents that is responsible for the full range of this adaptogenic.
Apart from that beta-glucans, part of the polysaccharides in Chaga, also have a positive effect on the normalization of cholesterol levels and blood sugar. Research showed betulinic acid (a compound unique to Chaga) to be able to break down ‘bad’ cholesterol in the bloodstream. By normalizing those levels Chaga contributes to lowering high blood pressure and promotes a healthy cardio-vascular system: less plaque, stronger arteries.
Research also showed DNA-regenerating and re-vitalizing properties. The whole body will benefit from this; you will look better (skin and hair) and your organs will function better. Check out this study published on Pubmed: http://www.ncbi.nlm.nih.gov/pubmed/18997282
I’ve only summarized a few benefits of chaga, for the most comprehensive article I’ve seen on chaga that doesn’t get into the internet hype going around, I recommend this blogpost: http://oriveda.wordpress.com/chaga-the-facts/
I get my chaga from Raw Revelations.