(See also Overview of Dietary Supplements.)
Milk thistle (Silybum marianum) is a purple-flowered plant. Its sap and seeds contain the active ingredient silymarin, a potent antioxidant and a term often used interchangeably with milk thistle. Silymarin can be further divided into 3 primary flavonoids: silybin, silydianin, and silychristin. Extracts of milk thistle should be standardized to 80 percent silymarin.
A 2007 Cochrane review of 13 randomized clinical trials assessed milk thistle in 915 patients with alcoholic and/or hepatitis B or C virus liver diseases (4). Data from this analysis determined that intervention had no significant effect on all-cause mortality, complications of liver disease, or liver histology. When all trials were included in the analysis, liver-related mortality was significantly reduced; however, in an analysis limited to high-quality studies, this reduction was not significant. Milk thistle was not associated with a significant increase in adverse effects. The design of these clinical trials did come into question, and the authors questioned the benefits of milk thistle and suggested the need for more well-designed placebo-controlled studies. In vitro, silymarin increases levels of intrahepatic glutathione, an antioxidant important for detoxification (5).
Another recent analysis of 9 randomized, placebo-controlled trials (487 patients) (2) indicates that milk thistle may improve glycemic control in type 2 diabetes; however, the studies were small and therefore further high-quality, large controlled trials using standardized preparation are needed before beneficial claims are justified.
Recently, 2 cases of Amanita mushroom ingestion poisoning (3) showed favorable results after treatment with silybin.
Loguercio C and Festi D. Silybin and the liver: From basic research to clinical practice. World J Gastroenterol 17(18):2288–2301, 2011.
Suksomboon N, Poolsup N, Boonkaew S, et al. Meta-analysis of the effect of herbal supplement on glycemic control in type 2 diabetes. J Ethnopharmacol 137(3):1328-1333, 2011.
Ward J, Kapadia K, Brush E, et al. Amatoxin poisoning: case reports and review of current therapies. J Emerg Med 44(1):116-121, 2013.
Rambaldi A, Jacobs BP, Gluud C. Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases. Cochrane Database Syst Rev (4)CD003620, 2007.
Valenzuela A, Aspillaga M, Vial S, et al. Selectivity of silymarin on the increase of the glutathione content in different tissues of the rat. Planta Med 55(5):420-422, 1989.
Wu JW, Lin LC, Tsai TH. Drug-drug interactions of silymarin on the perspective of pharmacokinetics. J Ethnopharmacol 121(2):185-193, 2009.
van den Bout-van den Beukel CJ, Koopmans PP, van der Ven AJ, et al. Possible drug-metabolism interactions of medicinal herbs with antiretroviral agents. Drug Metab Rev 38(3):477-514, 2006.