Milk thistle

Milk thistle
Milk thistle

Milk thistle (Silybum marianum or Cardus marianum) is a plant used for treating liver disorders, breastfeeding problems, and other illnesses. The active ingredient of the herb, silymarin, is found in the ripe seeds of the plant.

The milk thistle plant has a long stem, green leaves with white spots, and pink to purple spiky flowered head (which true to its name, resembles a thistle). The plant is native to Europe and grows in the wild in the United States and South America. Other common names for the plant include Mary thistle, St. Mary thistle, Marian thistle, and lady’s thistle.

The medicinal benefits of milk thistle have been valued for more than 2,000 years. Written records show that as early as the first century, Romans were using the plant as a liver-protecting agent.

The plant was also frequently used throughout the Middle Ages, and it is in the herbal literature of this period that the medicinal properties of milk thistle seeds are first noted.

Nicholas Culpepper, a British herbalist, wrote about the value of the herb in treating diseases of the liver and spleen in the late eighteenth century, and by the end of the next century, records show that American physicians were also prescribing the substance. Silymarin was first isolated from the milk thistle plant by German scientists in the 1960s.

The leaves and stem of the milk thistle plant are edible, and can be used in salads or eaten raw. The plant was cultivated as a vegetable in Europe through the end of the nineteenth century.

General use

Milk thistle flower
Milk thistle flower

Milk thistle is prescribed for a number of medicinal uses, including liver disease treatment and prevention, HIV treatment, lactation problems, gallbladder disorders, mushroom poisoning, and psoriasis, a chronic skin disease characterized by reddish patches.

Liver disease

Milk thistle is thought to promote the growth of new liver cells, and to prevent toxins from penetrating through healthy liver cells by binding itself to the cell membranes.

It is prescribed for cirrhosis, hepatitis, and other liver disorders. Several clinical studies have demonstrated that individuals with cirrhosis who take daily doses of milk thistle extract have a lower mortality rate than those who took a placebo (or sugar pill).

While further research needs to be completed, a 2001 article reports that clinical trials show that milk thistle (at 140 mg three times per day) did indeed improve survival among cirrhosis patients.

In addition, milk thistle may have a protective effect on the liver, and is sometimes prescribed for patients who take medications that can cause liver damage (e.g., Thorazine, Haldol), or those who are exposed to liver-damaging substances such as lead.

A large, controlled trial sponsored by the National Center for Complementary and Alternative Medicine (NCCAM) and the National Institutes of health (NIH) of milk thistle’s medicinal value in the treatment of hepatitis and liver injury was scheduled to begin in the year 2000.

HIV treatment

Milk thistle is sometimes prescribed for HIV-positive patients to protect the liver from diseases such as hepatitis and from the hepatotoxic effects of other medications prescribed for HIV treatment.

Lactation problems

Milk thistle is frequently prescribed for breastfeeding mothers to promote increased breast milk secretion. Although the herb is considered safe for nursing mothers, it should be acquired from a reputable source and prescribed by an herbalist, naturopathic physician, or other healthcare professional familiar with its use.

Cancer prevention

The active chemical components of the milk thistle, silymarin (a complex of flavonoids) and its constituent, silibin, act as antioxidants. These substances have been shown to slow cell growth in some types of cancer.

Gallbladder disorders

Milk thistle may prevent inflammation of the gallbladder ducts and clear up jaundice.

Death cap mushroom poisoning

Milk thistle is the only known antidote for death cap mushroom (Amanita phalloides) poisoning. Ingesting this deadly mushroom can destroy the liver by shutting down protein production in liver cells. Milk thistle neutralizes these toxins and protects the liver. Milk thistle may also be helpful in acetaminophen overdosage.


Because the liver neutralizes certain toxins associated with psoriasis attacks, milk thistle is believed to help prevent psoriasis outbreaks by promoting proper liver function.

Several other dermatological uses for the herb are currently under investigation. The antioxidant properties of the herb may have a healing effect on skin wounds and burns. Milk thistle has also been proposed as a cosmetic agent to retain skin tone and quality. Further studies are needed to prove the efficacy of the herb for these applications.


Milk thistle seeds
Milk thistle seeds

Milk thistle is available in seed form, in capsules, and in extracts and tinctures. A tincture is an herbal preparation made by diluting the herb in alcohol. Tinctures of milk thistle can be taken in 1 or 2 ml doses three times a day.

Milk thistle seed has a low level of water solubility, so infusions (or teas) made from the herb are weaker than milk thistle tinctures and extracts. An infusion of milk thistle can be prepared by pouring a cup of boiling water over one teaspoon of seeds that have been ground to a fine texture.

After the mixture steeps for 10-20 minutes, the herb is strained out and the mixture can be drunk. Instead of straining, the herb can also be placed into an infuser ball, tea bag, or a piece of cheesecloth or muslin and removed after steeping. Individuals can drink two to three cups of the infusion daily.

Milk thistle seed can also be taken by mouth in a dose of 1 tsp of fresh ground seeds daily. The herb should always be stored in an airtight container in a cool location away from bright light to maintain its potency.


Individuals who suspect they have a liver disorder should always seek care from a healthcare professional.

Milk thistle should always be obtained from a reputable source that observes stringent quality control procedures and industry-accepted good manufacturing practices.

Consumers should look for the designations “U.S.P.” (U.S. Pharmacopeia) or “NF” (National Formulary) on milk thistle labeling. Herbal preparations prepared under USP or NF guidelines meet nationally recognized strength, quality, purity, packaging, and labeling standards as recommended by the U. S. Food and Drug Administration (FDA).

Botanical supplements are regulated by the FDA; however, they currently do not have to undergo any approval process before reaching the consumer market, and are classified as nutritional supplements rather than drugs.

Legislation known as the Dietary Supplement Health and Education Act (DSHEA) was passed in 1994 in an effort to standardize the manufacture, labeling, composition, and safety of botanicals and supplements, and in January 2000, the FDA’s Center for Food Safety and Applied Nutrition (CFSAN) announced a 10-year plan for establishing and implementing these regulations by the year 2010.


Milk thistle is considered safe to use during pregnancy and in women who breastfeed. However, there are currently no long-term studies on use of the herb during pregnancy or lactation. A woman should speak with her healthcare practitioner before taking any herbs and/or medications during pregnancy.

Milk thistle farm
Milk thistle farm

Side effects

Milk thistle may cause mild nausea and diarrhea, or loose stools. The herb may also cause an allergic reaction in some individuals, particularly those with known allergies to plants in the Asteraceae family (thistles, daisies, artichokes).

No other widely reported side effects are known when milk thistle is taken in proper therapeutic dosages. However, people with chronic medical conditions should consult with their healthcare professionals before taking the herb.


There are no reported negative interactions between milk thistle and other medications and herbs, although certain drugs with the same therapeutic properties as milk thistle may enhance the effect of the herb. Again, individuals should consult their healthcare provider if they are taking other medications concurrently with milk thistle.