What is milk thistle?

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    Last Updated: May 16, 2025

    Milk thistle (Silybum marianum) is a medicinal plant from the Asteraceae family that is native to Southern Europe, Central Asia, and Ethiopia; it is known for its distinctive white-veined leaves and ability to grow up to 6 feet tall. It blooms from June to August and produces black seeds that are harvested for medicinal use, and its extracts contain 70% to 80% of the compound silymarin.

    Milk thistle (Silybum marianum) is a medicinal plant belonging to the Asteraceae/Compositae family. It is native to Southern Europe, Central Asia, and Ethiopia[1] and grows particularly well on the sunny slopes of the Mediterranean countries. Milk thistle’s leaves have characteristic white, “milky” veins, and the plant can grow up to 6 feet tall. It typically blooms from June to August, after which its black seeds are harvested to be used for medicinal purposes. Milk thistle can now be found throughout California, South America, Africa, Australia, and Asia.[2][3]

    Although the terms milk thistle and silymarin are often used interchangeably, silymarin is a complex extracted from the dried seeds and fruits of milk thistle.[2][4][5] Milk thistle extracts are typically odorless and contain 70–80% of silymarin.[6]