The liver is the body's main organ of detoxification. In a two-phase process, the liver is able to detoxify toxic substances, making them more water-soluble and therefore easier to excrete. Milk thistle helps protect the liver from potential damage caused by toxic substances.  By acting at the cell membrane of hepatocytes (liver cells), milk thistle helps prevent toxins from entering the cell and causing damage to healthy liver cells.  The active ingredient silymarin is effective at protecting the liver from acute and chronic exposure to toxins.  It also helps support the liver's antioxidant defenses, as this organ is consistently exposed to a variety of damaging free radicals.