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):
Science Ratings
Health Concerns
Alcohol-related liver disease
Hepatitis
Liver cirrhosis
Type 2 diabetes
Gallstones
Reliable and relatively consistent scientific data showing a substantial
health benefit.
Contradictory, insufficient, or preliminary studies suggesting a health
benefit or minimal health benefit.
For a herb, supported by traditional use but minimal or no scientific
evidence. For a supplement, 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 chemist, 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 anti-oxidant.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 make-up, 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 standardised 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 a few
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 medicines may interact with milk thistle. Refer to drug interactions for a
list of those medicines.
Drug Interactions
Certain medicines interact with milk thistle: Some interactions may increase the
need for milk thistle ( ), other interactions may be negative ( ) and indicate
milk thistle should not be taken without first speaking with your physician or
chemist, others may require further explanation ( ). Refer to the individual drug
article for specific details about an interaction.
Note: The following list only includes the generic or class name of a medicine. To
find a specific brand name, use the Medicines index.
Chemotherapy
Cisplatin
Clofibrate
Fluorouracil
General Anaesthetics
Haloperidol
Hydrocodone with Paracetamol
Lovastatin
Methotrexate
Metronidazole
Nitrous Oxide
Paclitaxel
Paracetamol
Paracetamol with Codeine
Pravastatin
Tacrine
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.