Silybum marianum (milk thistle) seeds have been used for 2000 years to treat chronic liver disease and protect the liver against toxins. Increasing research is being undertaken on the physiological effects, therapeutic properties and possible medical uses of milk thistle. Milk thistle is believed to give some remedy for liver diseases (e.g., viral hepatitis) and the extract, silymarin, is used in medicine. Mild gastrointestinal distress is the most common adverse event reported for milk thistle. Traditional milk thistle extract is made from the seeds, which contain approximately 4-6% silymarin.