Black Walnut [Intestinal] (Juglans nigra) is a rich source of the trace mineral chromium and is also high in iodine. The ancient Greeks used the hulls to support the intestinal system and to treat skin infections. Herbalists classify black walnut as an astringent because it is rich in tannin, a toning substance. Black walnut's fame in folk medicine is due to its cleansing properties. The unripe hulls of the black walnut are high in vitamin C. Available in capsules and in an alcohol-base liquid form. Each capsule contains 500 mg black walnut. Take 2 capsules with a meal twice daily; for liquid, take 20-25 drops (1 ml) with water twice daily.