Milk thistle (Silybum marianum) seed extract

Milk thistle (Silybum marianum) seed extract, also known as Lady’s Thistle and St. Mary’s Thistle, has been used by herbalists for thousands of years, particularly because of its ability to function as an hepatoprotective (i.e., liver protective) agent. Constituents of particular interest are the complex mixture of multiple flavanolignans derived from the fruit that are known collectively as silymarin (silybin A and B, silychristin, silydianin, isosilybin and 2,3-dehydro derivatives). The terms “milk thistle” and “silymarin” are often used interchangeably. The fruit of milk thistle also contains flavonoids, lipids, sterols, sugars, amines and saponins 1.

Traditional uses of milk thistle for protection of the liver have triggered clinical studies attempting to validate the hepatoprotective benefits of a variety of milk thistle extract preparations for individuals with health conditions. Some 2,3,4,5,6,7,8 but not all 9,10,11,12 studies have shown that oral intake of milk thistle extracts can benefit the liver. When used appropriately, milk thistle extracts have been safe when used for as long as six years. Daily intake of silymarin has ranged from 140-2,100 mg/day 3,9. When reported, most noted adverse reactions have been mild 2,6,8,10,11,12.

This ingredient can be found in the following products in United States:


  1. Barnes J, Anderson LA, Phillipson JD. Herbal Medicines. A Guide for Healthcare Professionals. Chicago, Ill.: Pharmaceutical Press, 2002.
  2. Freedman ND, Curto TM, Morishima C et al. Aliment.Pharmacol Ther. 2011;33:127-37.
  3. El-Kamary SS, Shardell MD, bdel-Hamid M et al. Phytomedicine. 2009;16:391-400.
  4. Saller R, Brignoli R, Melzer J, Meier R. An updated systematic review with meta-analysis for the clinical evidence of silymarin. Forsch Komplementmed. 2008;15:9-20.
  5. Velussi M, Cernigoi A, Viezzoli L. Curr Ther Res 1993;53:533-45.
  6. Ferenci P, Dragosics B, Dittrich H et al. J Hepatol 1989;9:105-13.
  7. Szilard S, Szentgyorgyi D, Demeter I. Protective effect of Legalon in workers exposed to organic solvents. Acta Med Hung. 1988;45:249-56.
  8. Salmi HA, Sarna S. Effect of silymarin on chemical, functional, and morphological alterations of the liver. A double-blind controlled study. Scand J Gastroenterol. 1982;17:517-21.
  9. Fried MW, Navarro VJ, Afdhal N et al. JAMA. 2012;308:274-82.
  10. Parés A, Planas R, Torres M et al. J Hepatol 1998;28:615-21.
  11. Bunout D, Hirsch S, Petermann M et al. Rev Med Chil. 1992;120:1370-5.
  12. Trinchet JC, Coste T, Levy VG et al. Gastroenterol Clin Biol. 1989;13:120-4.