Because milk thistle promotes liver function and helps it process cholesterol, it benefits cardiovascular health by maintaining cholesterol levels that are already in the normal range. Milk thistle extract has been studied primarily for its effects on liver health. Milk thistle seeds yield the most active ingredient, silymarin, a nutrient complex made up of numerous flavonoid antioxidants, including silybinin. Milk thistle is widespread in many parts of the world and is especially prized for its seeds, which have long been used in European folk medicine. Milk thistle supplements come in a variety of forms, including capsules, tablets and liquids. Some of these supplements can be standardized to provide guaranteed minimum levels of silymarin, milk thistle’s most active component. There is no fixed dosage of milk thistle. Milk thistle extract is usually obtained from the seeds of the plant. Before you start taking milk thistle extract, discuss its use with your doctor. Studies have shown that the antioxidants in silymarin act against harmful free radicals in the liver, providing a protective effect. Silymarin has also been studied for its effect on cholesterol balance. Silymarin may also improve protein synthesis in the liver and stimulate liver cell regeneration. **These claims have not been evaluated by the Food and Drug Administration.