Information about the herb St Mary’s Thistle

 Silybum marianum, also known as Milk Thistle is part of the Compositae plant family. St. Mary’s Thistle is native to the Mediterranean, Europe and Asia and grows wild throughout Europe, North America and Australia. 

General Information

Thistle is an old English name for a large family of plants occurring chiefly in Europe and Asia. There are 14 species of Thistles just in Great Britain.

Botanical Name:  Silybum marianum

Plant Family: Compositae

Common Names:  Milk Thistle, Marian Thistle  

History:  The use of St. Mary’s Thistle was recorded in the first century (AD 23-79) noting that the plant was excellent for protecting the liver. Early Christian tradition dedicated the plant to Mary, calling it Marian Thistle

In the 19th century the Eclectics used the herb for:

  • congestion in the liver, spleen and kidneys.
  • menstrual difficulties
  • varicose veins

According to the herbalist Culpepper, ‘Thistles, in general, are under the dominion of the planet, Jupiter’.

Tradition: This thistle supposedly gets its name because the milk white veins of the leaves originated in the milk of the Virgin which once fell upon a plant of thistle.

An old Saxon tradition said that if:

  • sprinkled around the home
  • worn near the person
  • it ‘setteth snakes to flight’ [kept snakes away]

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Plant Constituents of St Mary’s Thistle


  • Silybin (the active chemical component) is one of the most potent liver protective agents. An injection of silybin is a proven antidote for poisoning with the Deathcap mushroom (Amanita phalloides).


  • antioxidant (more potent than Vitamins C and E)
  • demulcent [a substance that soothes irritated tissue, particularly mucous membranes]
  • galactagogue [an agent that encourages or increases the secretion of milk]
  • inhibits the factors responsible for liver damage
  • stimulates production of new liver cells to replace old damaged ones

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Usage of St Mary’s Thistle

Medicinal Parts Used:   Whole herb, roots, leaves, seeds and hull

St. Mary’s Thistle is used for:

Brain and Nervous System Conditions

  • depression
  • severe melancholy

Female Conditions

  • increases breast-milk production

Genitourinary Conditions

  • breaks and expels stones
  • dropsy

Inflammatory Conditions

  • catarrh

Liver conditions

St. Mary’s Thistle supports nutritionally the liver’s ability to maintain normal liver function. It has been used to treat nearly every known form of liver disease including:

  • biliary derangements
  • cirrhosis
  • hepatitis
  • jaundice
  • liver damage due to drug and alcohol abuse
  • necroses
  • removing obstructions from liver and spleen
  • skin conditions related to poor liver function
  • stimulating the secretion of bile
  • the liver detoxification process

It protects the liver from damage from the harmful, detrimental effects of:

  • alcohol
  • chemotherapy
  • drugs
  • environmental toxins
  • by fighting pollutants, preventing free radical damage and stimulating the production of new liver cells

Respiratory Tract Conditions

  • pleurisy


  • tinnitis (ringing in ears) combined with Ginkgo biloba

Other Uses:

The leaves are nutritious:

  • when steamed
  • in a salad when young and tender

St.Mary’s Thistle has similar properties to Blessed Thistle



Recommended dose:


  • dried herb 12 to 15g/day
  • capsules/trablets 200-400 mg/day
  • liquid herbal extract 30-60mL/week

For liver protection:

  • 120 mg silymarin (about 2 capsules twice/day)
  • To treat liver damage (from alcohol, drugs, or chemicals)
  • 120 mg (about 3 capsules), 3 times/day

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St. Mary’s Thistle should not be used by:

  • pregnant or breastfeeding women

Side effects from St. Mary’s Thistle happen only rarely, but may include:

  • anaphylaxis, a life-threatening allergic reaction that causes: 
  • throat tightness
  • shortness of breath
  • loss of consciousness
  • diarrhea
  • stomach pain
  • headache
  • impotence
  • joint pain
  • nausea and vomiting
  • rash
  • skin reactions

The last two reactions listed are extremely rare.

Drug Interactions:

If you are currently being treated with any of the following medications, you should not use milk thistle without first talking to your healthcare provider.

Similar to its ability to protect against damage to the liver from alcohol and acetominophen, as discussed in the Overview, milk thistle may also protect against liver damage from the following medications:

  • Antipsychotics: This group of medications used for schizophrenia includes butyrophenones (such as haloperidol) and phenothiazines (such as chlorpromazine, fluphenazine, and promethazine)
  • Phenytoin: a medication used for seizures
  • Halothane: a medication used during general anesthesia

Other medications that may interact with milk thistle include:


One animal study found that milk thistle may enhance the effectiveness of aspirin in rats with liver cirrhosis. Whether this herb-drug combination has the same effect in people is not known at this time.

Chemotherapy medications

Preliminary research suggests that silybin may enhance the tumor fighting effects of cisplatin and doxorubicin when tested against breast and ovarian cancer cells.

In addition, milk thistle may protect the kidneys against toxic side effects associated with cisplatin and cyclosporine, two medications that are commonly used to treat cancer.

On the other hand, a different laboratory study revealed that the anticancer effect of cisplatin and ifosfamide was diminished in the presence of milk thistle. More research needs to be done to assess how milk thistle and cancer-fighting agents interact.

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Global Herbal Supplies has St Mary’s Thistle available in the following forms