Milk thistle is a medicinal plant which has been used for over 2,000 years as a herbal remedy for a variety of diseases, particularly for the liver, kidney and gallbladder. Studies dating back to the first century indicate the use of this plant by the Romans as a liver protector. Clinical studies suggest that substances in milk thistle, especially similarina, a flavonoid, can benefit the liver by protecting and promoting cell growth and inhibit oxidation and inflammation.