Nutritional Supplement

Milk Thistle

Parts Used & Where Grown

Milk thistle is commonly found growing wild in a variety of settings, including roadsides. The dried fruit (also called achenes) are used to produce modern herbal extracts.

How It Works

The dried fruit of milk thistle contain a flavonoid complex known as silymarin. This constituent is responsible for the medical benefits of the plant.1 Silymarin is made up of three parts: silibinin, silidianin, and silicristin. Silibinin is the most active and is largely responsible for the benefits attributed to silymarin.2

Milk thistle extract may protect the cells of the liver by blocking the entrance of harmful toxins and helping remove these toxins from the liver cells.3,4 As with other bioflavonoids, silymarin is a powerful antioxidant.5 Silymarin has also been shown to regenerate injured liver cells.6 Recent studies have shown that silymarin has the ability to block fibrosis, a process that contributes to the eventual development of cirrhosis in people with inflammatory liver conditions secondary to diseases such as alcohol abuse or hepatitis.7

Milk thistle extract is most commonly recommended to counteract the harmful actions of alcohol on the liver. Double-blind trials indicate that it helps the liver return to a healthy state once a person stops drinking.8,9 Some trials suggest it may improve quality of life and even life expectancy in people with liver cirrhosis.10,11 However, another trial found no effect in cirrhosis patients.12 Milk thistle alters bile makeup, thereby potentially reducing risk of gallstones.13 However, this needs to be verified by human clinical trials. Milk thistle extract has been shown to protect the liver from the potentially damaging effect of drugs used to treat schizophrenia and other forms of psychosis.14 However, one trial found that it did not protect the liver from the potentially harmful effects of the drug Cognex (tacrine hydrochloride) used to treat early-stage Alzheimer’s disease. 15


1. Wagner H, Horhammer L, Munster R. The chemistry of silymarin (silybin), the active principle of the fruits of Silybum marianum (L.) Gaertn. Arzneim-Forsch Drug Res 1968;18:688-96.

2. Hikino H, Kiso Y, Wagner H, Fiebig M. Antihepatotoxic actions of flavonolignans from Silybum marianum fruits. Planta Medica 1984;50:248-50.

3. Faulstich H, Jahn W, Wieland T. Silibinin inhibition of amatoxin uptake in the perfused rat liver. Arzneimittelforschung 1980;30:452-4.

4. Tuchweber B, Sieck R, Trost W. Prevention by silibinin of phalloidin induced hepatotoxicity. Toxicol Appl Pharmacol 1979;51:265-75.

5. Feher J, Lang I, Deak G, et al. Free radicals in tissue damage in liver diseases and therapeutic approach. Tokai J Exp Clin Med 1986;11:121-34.

6. Sonnenbichler J, Zetl I. Stimulating influence of a flavonolignan derivative on proliferation, RNA synthesis and protein synthesis in liver cells. In Assessment and Management of Hepatobiliary Disease, ed. L Okolicsanyi, G Csomos, G Crepaldi. Berlin: Springer-Verlag, 1987, 265-72.

7. Schuppan D, Strösser W, Burkard G, Walosek G. Legalon® lessens fibrosing activity in patients with chronic liver diseases. Zeits Allgemeinmed 1998;74:577-84.

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. Leng-Peschlow E. Alcohol-related liver diseases-use of Legalon®. Z Klin Med 1994;2:22-7.

10. Ferenci P, Dragosics B, Dittrich H, et al. Randomized controlled trial of silymarin treatment in patients with cirrhosis of the liver. J Hepatol 1989;9:105-13.

11. Velussi M, Cernogoi AM, De Monte A, et al. Long-term (12 months) treatment with an antioxidant drug (silymarin) is effective on hyperinsulinemia, exogenous insulin need and malondialdehyde levels in cirrhotic diabetic patients. J Hepatology 1997;26:871-9.

12. Parés A, Planas R, Torres M, et al. Effects of silymarin in alcoholic patients with cirrhosis of the liver: results of a controlled, double-blind, randomized and multicenter trial. J Hepatol 1998;28:615-21.

13. Nassuato G, Iemmolo RM, et al. Effect of silibinin on biliary lipid composition. Experimental and clinical study. J Hepatol 1991;12:290-5.

14. Palasciano G, Portinascasa P, Palmieri V, et al. The effect of silymarin on plasma levels of malondialdehyde in patients receiving long-term treatment with psychotropic drugs. Curr Ther Res 1994;S5:S37-45.

15. Allain H, Schück S, Lebreton S, et al. Aminotransferase levels and silymarin in de novo tacrine-treated patients with Alzheimer's disease. Dementia Geriatr Cogn Disorders 1999;10:181-5.

16. Ebrahimpour-Koujan S, Gargari B, Mobasseri M, et al. Lower glycemic indices and lipid profile among type 2 diabetes mellitus patients who received novel dose of Silybum marianum (L.) Gaertn. (silymarin) extract supplement: A Triple-blinded randomized controlled clinical trial. Phytomedicine 2018;44:39–44.

17. Ebrahimpour Koujan S, Gargari B, Mobasseri M, et al. Effects of Silybum marianum (L.) Gaertn. (silymarin) extract supplementation on antioxidant status and hs-CRP in patients with type 2 diabetes mellitus: a randomized, triple-blind, placebo-controlled clinical trial. Phytomedicine 2015;22:290–6.

18. Huseini H, Larijani B, Heshmat R, et al. The efficacy of Silybum marianum (L.) Gaertn. (silymarin) in the treatment of type II diabetes: a randomized, double-blind, placebo-controlled, clinical trial. Phytother Res 2006;20:1036–9.

19. Di Pierro F, Bellone I, Rapacioli G, Putignano P. Clinical role of a fixed combination of standardized Berberis aristata and Silybum marianum extracts in diabetic and hypercholesterolemic patients intolerant to statins. Diabetes Metab Syndr Obes 2015;8:89–96.

20. Di Pierro F, Putignano P, Villanova N, et al. Preliminary study about the possible glycemic clinical advantage in using a fixed combination of Berberis aristata and Silybum marianum standardized extracts versus only Berberis aristata in patients with type 2 diabetes. Clin Pharmacol 2013;5:167–74.

21. Nassuato G, Iemmolo RM, et al. Effect of silibinin on biliary lipid composition. Experimental and clinical study. J Hepatol 1991;12:290-5.

22. Brown DJ. Herbal Prescriptions for Better Health. Rocklin, CA: Prima Publishing, 1996, 151-8.

23. Reyes H. The spectrum of liver and gastrointestinal disease seen in cholestasis of pregnancy. Gastroert Clin N Am 1992;21:905-21.

24. Adverse Drug Reactions Advisory Committee. An adverse reaction to the herbal medication milk thistle (Silybum marianum). MJA 1999;170:218-9.

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The information presented by Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2020.