Holland & Barrett Effervescent Milk Thistle Extract 100mg Milk thistle (Silybum marianum) is one of the most well-researched herbal ingredients in natural medicine, with centuries of traditional use for liver and digestive health. Its primary active constituent, silymarin (a group of flavonolignans), is associated with antioxidant activity and liver-protective properties. Holland & Barrett provides a highly concentrated 25:1 extract in a convenient, pleasant-tasting effervescent format, making it an accessible daily supplement. The effervescent delivery may also improve absorption compared to traditional hard tablets