From the Manufacturer:
Black Walnut [Intestinal] The ancient Greeks used the hulls of black walnut to support the intestinal system and the skin. Herbalists classify black walnut as an astringent because it is rich in tannins, which have toning properties. Black walnut’s fame in folk herbology is due to its cleansing properties. The unripe hulls of the black walnut contain vitamin C and the trace minerals chromium and iodine.