Birch trees grow in extreme climates like the Northern United States, Canada and Siberia. Temperatures can get very cold in these places, as low as -94 degrees Fahrenheit. This means the birch tree must be resilient enough to live through these harsh winters. The birch tree survives these extreme temperatures by producing sterols to buffer the cold. These sterols get absorbed by the Chaga as it grows. Inotodiol, Betulin, and Betulinic acid are among these sterols, which help give Chaga its health benefits. Research has shown that only Chaga harvested from birch trees thriving in these harsh conditions contain Betulin, Betulinic Acid, and Melanin.