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Photo copyright Steven Foster

Milk Thistle

Common names: Holy thistle, Marythistle, St. Mary’s thistle, Marian thistle

Botanical names: Silybum marianum, Carduus marianus

Parts used and 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.



Milk Thistle has been used in connection with the following conditions (refer to the individual health concern for complete information):

Rating Health Concerns
3Stars Alcohol-related liver disease
2Stars Hepatitis
Liver cirrhosis
1Star Gallstones
3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.

Historical or traditional use (may or may not be supported by scientific studies): Medical use of milk thistle can be traced back more than 2,000 years. Nicholas Culpeper, the well-known 17th-century pharmacist, cited its use for opening “obstructions” of the liver and spleen and recommended it for the treatment of jaundice.

Active constituents: 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

How much is usually taken? For liver disease and impaired liver function, research suggests the use of 420–600 mg of silymarin per day from an herbal extract of milk thistle standardized to 80% silymarin content.16 According to research and clinical experience, improvement should be noted in about eight to twelve weeks. For people with chronic liver disease, milk thistle extract may be considered a long-term therapy.

For those who prefer, 12–15 grams of milk thistle dried fruits can be ground and eaten or made into a tea. This should not be considered therapeutic for conditions of the liver, however.

Are there any side effects or interactions? Milk thistle extract is virtually devoid of any side effects and may be used by most people, including pregnant and breast-feeding women. In fact, it has been recommended as a treatment for itching due to poor gallbladder function during pregnancy.17 Since silymarin stimulates liver and gallbladder activity, it may have a mild, transient laxative effect in some people. This will usually cease within two to three days.

There is one case report of a 57-year-old Australian woman experiencing several episodes of nausea, abdominal pain, vomiting and weakness after taking a milk thistle preparation.18 This case is so atypical, however, that the Adverse Drug Reactions Advisory Committee of Australia questioned whether the product taken might not have contained other herbs or additives that could be responsible for the adverse reaction.

Are there any drug interactions? Certain medications may interact with milk thistle. Refer to the drug interactions safety check for a list of those medications.

References:

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. Arzneim-Forsch Drug Res 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, Sama S. Effect of silymarin on chemical, functional and morphological alterations of the liver. 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. Pares A, Plancs 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, Strazzabosco M, 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. Brown DJ. Herbal Prescriptions for Better Health. Rocklin, CA: Prima Publishing, 1996, 151–8.

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

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