This study examined chaga mushroom, a traditional medicine used against cancer, grown on two types of birch trees. Researchers tested chaga extracts on 31 different cancer cell types and found they were moderately effective at inhibiting cancer cell growth, particularly against liver and thyroid cancers. The chaga from silver birch (B. pendula) worked slightly better than that from downy birch (B. pubescens) due to higher levels of a compound called inotodiol.