Our Birch Leaf Extract has an extract ratio of 5:1. It is obtained from the leaf of Birch (Betula alba L). Birches are deciduous trees that are native to Europe and growing from Central Europe to Siberia. Birch leaves contain Flavonoids and other Polyphenols. Birch leaves have been used since the ancient Greeks and Romans. They are said to have diuretic properties that promote flushing of the urinary tract.