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Milk thistle seed is used in herbal medicine for liver and gall bladder conditions

Milk Thistle

Silybum marianum Asteraceae

Milk thistle's traditional reputation as a liver tonic is now supported by extensive research. Modern herbalists use milk thistle for a variety of digestive conditions. It is also used as a standardised extract for the treatment of various liver conditions.

Sustainability status

Not currently on risk lists but complete data may be missing on the status of the species. Commonly cultivated though may be sourced from the wild. Only source cultivated supplies or from certified sustainable wild collection. Read more about our sustainability guide.

Sustainability Status
Key benefits
  • Liver protective
  • Liver tonic
  • Gall stones
  • Dyspepsia
  • How does it feel?

    Milk thistle is a refreshingly sweet and aromatic medicine that is much easier to tolerate than the usual bitter liver herbs. It works best as an alcoholic extract, powdered or dried seed preparation.

  • What can I use it for?

    Milk thistle plant (Silybum marianum)
    Milk thistle plant (Silybum marianum)

    Milk thistle is well known as a liver herb that is safe for all to use to support this important detoxification system. It works via a direct stimulating effect on the liver, which also encourages the flow of bile. Milk thistle is also both a restorative and protector of the liver. It encourages optimum function of the liver and gall bladder – offering a wide range of therapeutic benefits such as better detoxification of the blood as well as improving the assimilation of fat-soluble nutrients.

    Milk thistle’s protective and rejuvenating effect on liver cells has been well documented in modern research. This includes support where there has been exposure to high levels of chemicals and pollution, whether through diet, medication or unprotected contact.

    As the name alludes in the ‘Doctrine of Signatures’ milk thistle is used as a galactagogue- to enhance the flow of breast milk and care for the young. The ‘milky’ white veins are a helpful ‘sign’ and a pointer of its benefits.

    Milk thistle is also a useful remedy for dyspepsia and digestive complaints of that are associated with a sluggish liver, after serious conditions have been ruled out (3).

  • Into the heart of Milk Thistle

    Milk thistle has a sweet, warming and nourishing action. Due to its milder bitter flavour it is useful for those with a colder constitution or for people who are depleted and require nourishing restorative support alongside detoxification. Milk thistle’s warming energetics also have a decongestant effect on stuck and stagnant blood flow resulting from its ability to reduce and eliminate toxicity from the blood (8).

    Matthew Wood recommends it for people with dry constipation that is relating to liver congestion and lack of bile. This type of constipation will usually present as hard and small (rabbit droppings) or they may also be pale in colour due to lack of bile. They might also float rather than sinking, which can indicate poor fat absorption (8).

  • Traditional uses

    Milk thistle has been used for more than 2000 years for diseases of the liver and gallbladder (4). In Europe, milk thistle was used traditionally for curing jaundice and for inflammation in the biliary ducts. It was also traditionally used for hepatitis and haemorrhoids (1).

    Dioscorides referred to milk thistle as a remedy for venomous snake bites, whilst Culpepper discusses an infusion made with both the seeds and root for disintegrating and expelling gall stones (1).

    Traditionally, milk thistle was used by nursing mothers for increasing milk production. As a bitter tonic, it has also had a long history of use for supporting the digestive system. It is referenced also as a demulcent to reduce inflammation topically and as an antidepressant and for dyspeptic complaints (4).

  • Traditional actions

  • What practitioners say

    Milk thistle leaves (Silybum marianum)
    Milk thistle leaves (Silybum marianum)

    Digestive system

    Some of the primary uses for milk thistle are centred around the liver gall bladder and its associated systems. Herbalists may use milk thistle as a part of a supportive treatment for all manner of liver diseases including for cirrhosis, fatty liver, hepatitis and other liver function abnormalities (1). Milk thistle is also indicated for liver problems that may occur in relation to medicines, chemical exposure or environmental pollutants (1).

    A number of mechanisms have been identified as being involved in milk thistle’s effects on the liver. It works by stabilising and protecting the hepatocyte membrane against injury, as well as regulating its permeability (1). It has also been shown to increase the proliferation of important liver cells called Kuppfer cells (which are involved in the breakdown of blood cells in the liver) (11).

    Metabolic

    Milk thistle has potent free radical scavenging properties. It is used to improve detoxification mechanisms and improve cellular regeneration (1). Milk thistle is also indicated in a number of conditions that are caused by oxidative stress and where there has been exposure to pollutants, chemicals are other toxins (1). 

    Mistletoe may also sometimes be applied for treatment and prevention of blood sugar conditions such as diabetes. It may be most relevant for use where liver conditions are accompanied by a diabetic predisposition or to help lower blood glucose levels in diabetes type 2 patients alongside conventional treatment (7).

    Milk thistle can be used to support phase 1 and phase 2 detoxification pathways. The phase 1 pathway attempts to break down compounds for excretion via oxidation, hydrolysis or reduction reactions facilitated by the cytochrome P-450 enzyme system. If that doesn’t work, the compounds go into phase 2 where other molecules (such as cysteine, glutathione, or sulphur) are added to make the initial compound suitable for excretion. It is then excreted through the bile into the bowel or eliminated as water-soluble compounds via the bladder (9).

  • Research

    Milk thistle seeds (Silybum marianum)
    Milk thistle seeds (Silybum marianum)

    There are a fair number of high-quality clinical trials on milk thistle. Most studies have investigated the isolated compound silymarin or its most active isomer silybin, rather than the herbal plant in its whole form. A number of these studies have been included below to demonstrate the evidence base for the medicinal actions discussed in this monograph.

    Most studies have been carried out on extracts that contain between 60-80% silymarin (1). Many trials using the standardised extract of milk thistle support the clinical indications for both non-alcoholic and alcoholic fatty liver disease/ damage as well as for cirrhosis, fatty liver, exposure to chemical pollutants (such as drugs, halogenated hydrocarbons, solvents, paints, glues and anaesthesia) and even for the treatment of death cap poisoning (1).

    A review of clinical studies evaluating the safety and efficacy of milk thistle

    In this review, a number of experimental and high-quality clinical studies confirmed a number of effects such as anticancer, antidiabetic, and cardioprotective properties of milk thistle extracts. Milk thistle also has a strong body of evidence for mechanisms by which it protects the liver against toxins as well as for its ability to therapeutically assist in chronic liver diseases (3).

    Meta-analysis and systematic review of milk thistle for the treatment of liver disease

    A systematic review of available literature was carried out to determine the efficacy and safety of milk thistle for the treatment of liver disease. The fourteen trials included in this review support the use of milk thistle in the treatment of liver disease (5).

    The therapeutic potential of milk thistle in diabetes

    A review was carried out to analyse the available literature surrounding the use of milk thistle for blood sugar abnormalities such as diabetes. Numerous studies showing milk thistles efficacy were included in this review, including human studies, in vitro and in vivo studies. Compounds of milk thistle, namely silibin have been shown to produce beneficial effects on several diabetic complications, including diabetic neuropathy, diabetic nephropathy, and non-alcoholic steatohepatitis. These effects are thought to be mainly in relation to the anti-oxidant properties of milk thistle (7).

  • Did you know?

    There is a group of polyphenols called flavolignans, which one of the main compounds of milk thistle silymarin is a part of. These have a protective and rejuvenating effect on liver cells, so much show that it has been shown to neutralise the toxic effects of one of nature’s most poisonous mushrooms- Amanita phalloids. This mushroom is known as ‘the avenging angel’, and produces the liver-destroying alkaloids amanantine and phalloidine. A treatment has now been developed into an injectable form for acute poisoning (3).

Additional information

  • Botanical description

    Milk thistle is a robust biennial thistle, forming a rosette of large, spiny dark green leaves with prominent white veins (variegated) that can be 3 inches across. It has purple flower heads with spiny bracts, in the second year. The bluish-purple seed head reaches 4′ tall.

  • Common names

    • Blessed thistle
    • Marian thistle
    • Mary thistle
    • Saint Mary’s thistle
    • Mediterranean milk thistle
    • Variegated thistle
    • Scotch thistle
  • Safety

    Milk thistle is safe to use during pregnancy and lactation (1).

  • Interactions

    None known

  • Contraindications

    Not recommended for anyone with a known sensitivity to plants in the daisy (Asteraceae family).

  • Preparation

    • Liquid extract
    • Decoction
    • Capsules
  • Dosage

    Liquid extract (1:1): Take between 4- 9ml a day.

    Decoction: To make a decoction place between 4-9 grams of dried seed in one cup of boiling water, simmer gently for between 15- 20 minutes. This should be drunk hot daily up to three times a day.

    Capsules and tablets: There are many readily available capsules or tablets that are standardised to contain a minimum of 200mg silymarin. These should be employed to treat more severe cases of liver damage. For severe liver damage, high doses are recommended to optimise treatment outcomes. The availability of silymarin is enhanced by the consecutive supplementing of lecithin (1). For serious conditions like this, one should always consult a clinical herbalist.

  • Plant parts used

    It is mainly the seed which is used for the conditions discussed in this monograph. Milk thistle leaf as well as root is also sometimes used.

  • Constituents

    One of the most important pharmacological compounds in milk thistle is a complex mixture of flavonolignans called silymarin. The constituents that make up silymarin are the flavonolignan isomers silybins A and B, isosilybins A and B, silychristin (also known as silichristin), silydianin (also known as silidianin), and their flavonoid precursor, taxifolin these are often referred to as silibinins (4).

    Milk thistle also contains fixed oil, flavonoids, taxifolin, sterols (1) as well as oleic and linoleum acid (6). It is the fixed oil fraction of milk thistle that gives it its milky colour (1).

Milk thistle illustration
  • Habitat

    Milk thistle is native to the Mediterranean region. It is mostly found in disturbed areas, such as pastures, roadsides, ditches, and fencerows.

  • Sustainability

    According to the IUCN Red List of Threatened Plants Status milk thistle is classified as least concern due to stable populations in most of its native habitats (9).

    Habitat loss and over-harvesting from the wild are two of the biggest threats faced by medicinal plant species. There are an increasing number of well-known herbal medicines at risk of extinction. We must therefore ensure that we source our medicines with sustainability in mind. 

    The herb supplement industry is growing at a rapid rate and until recent years a vast majority of medicinal plant produce in global trade was of unknown origin. There are some very real and urgent issues surrounding sustainability in the herb industry. These include environmental factors that affect the medicinal viability of herbs, the safety of the habitats that they are taken from, as well as the welfare of workers in the trade.

    The botanical supply chain efforts for improved visibility (transparency and traceability) into verifiably sustainable production sites around the world are now certificated through the emergence of credible international voluntary sustainability standards (VSS). 

    Read our article on  Herbal quality & safety: What to know before you buy and Sustainable sourcing of herbs to learn more about what to look for and questions to ask suppliers about sustainability.

  • Quality control

    Herbal Medicines are often extremely safe to take, however it is important to buy herbal medicines from a reputed supplier. Sometimes herbs bought from unreputable sources are contaminated, adulterated or substituted with incorrect plant matter.

    Some important markers for quality to look for would be to look for certified organic labelling, ensuring that the correct scientific/botanical name is used and that suppliers can provide information about the source of ingredients used in the product.

    A supplier should be able to tell you where the herbs have come from. There is more space for contamination and adulteration when the supply chain is unknown.

  • How to grow

    Milk thistle tea (Silybum marianum)
    Milk thistle tea (Silybum marianum)

    Milk thistle can be grown as a winter annual or a biennial which means that it dies once it has flowered and produced seeds. However, it usually self-seeds in the vicinity, so take care to keep the plants under control 

    Either sow seeds in early spring for late summer flowering, or sow in late summer for flowering in early summer the following year. Either way, as these are large seeds that germinate and grow quickly, we recommend sowing the seeds directly into pots (rather than trays) – one seed per pot.

    If you sow in the spring, sow indoors and plant out as soon as they are big enough to handle. Space the plants at least 2-3 feet apart and allow plenty of space for paths (the spiky leaves will stop all traffic on your paths if you don’t). If you sow in late summer, sow outdoors and move the pots indoors for the winter, then plant out the following spring. Late summer sowing normally produces higher seed yields.

  • References

    1. Bone, K. (n.d.). Principles and practice of phytotherapy : modern herbal medicine. Elsevier Uuuu-Uuuu.
    2. (No date) European Union herbal monograph on Silybum Marianum (L.) gaertn., fructus. Available at: https://www.ema.europa.eu/en/documents/herbal-monograph/draft-european-union-herbal-monograph-silybum-marianum-l-gaertn-fructus_en.pdf (Accessed: 18 December 2023). 
    3. Saller, R., Brignoli, R., Melzer, J., & Meier, R. (2008). An Updated Systematic Review with Meta-Analysis for the Clinical Evidence of Silymarin. Forschende Komplementärmedizin / Research in Complementary Medicine, 15(1), 9–20. https://doi.org/10.1159/000113648
    4. Milk Thistle (PDQ®)–Health Professional Version – National Cancer Institute. (2003, December 23). www.cancer.gov. https://www.cancer.gov/about-cancer/treatment/cam/hp/milk-thistle-pdq
    5. Saller, R., Brignoli, R., Melzer, J., & Meier, R. (2008). An Updated Systematic Review with Meta-Analysis for the Clinical Evidence of Silymarin. Forschende Komplementärmedizin / Research in Complementary Medicine, 15(1), 9–20. https://doi.org/10.1159/000113648
    6. DOĞAN, G., KARA, N., GÜR, S., & BAGCI, E. (2022). Chemical Composition and Biological Activity of Milk Thistle Seeds (Silybum marianum (L.) Gaertn.). International Journal of Nature and Life Sciences, 90–98. https://doi.org/10.47947/ijnls.1124453
    7. Wood, M. (). The earthwise herbal : a complete guide to Old World medicinal plants. North Atlantic Books.
    8. Not for Public Distribution. For Education of Health Care Professionals Only. 1 Herbs for Enhancing Phase I/II Hepatic Detoxification Key Points at a Glance Detoxification in the Liver. (2011). https://assets-us-01.kc-usercontent.com/b3f5510f-b2f6-0081-05a1-dbd7a9328e1f/16b1a3a5-b32a-4fb2-98a7-d5dd8d3d7ae0/2011-pp-no-56_au.pdf
    9. Khela, S., & RBG, R. (2019, August 28). IUCN Red List of Threatened Species: Silybum marianum. IUCN Red List of Threatened Species; Name. https://www.iucnredlist.org/species/202991/88329022
    10. Rainone, F. (2005). Milk Thistle. American Family Physician, 72(7), 1285–1292. https://www.aafp.org/pubs/afp/issues/2005/1001/p1285.html#:~:text=In%20some%20studies%2C8%20milk
Aromatic
An ‘aromatic’ remedy, high in volatile essential oils, was most often associated with calming and sometimes ‘warming’ the digestion. Most kitchen spices and herbs have this quality: they were used both as flavouring and to ease the digestion of sometimes challenging pre-industrial foods. Many aromatics are classed as ‘carminatives’ and are used to reduce colic, bloating and agitated digestion. They also often feature in respiratory remedies for colds, chest and other airway infections. They are also classic calming inhalants and massage oils, and are the basis of aromatherapy for their mental benefits.
Astringent taste
The puckering taste you get with many plants (the most familiar is black tea after being stewed too long, or some red wines) is produced by complex polyphenols such as tannins. Tannins are used in concentrated form (eg from oak bark) to make leather from animal skins. The process of ‘tanning’ involves the coagulation of relatively fluid proteins in living tissues into tight clotted fibres (similar to the process of boiling an egg). Tannins in effect turn exposed surfaces on the body into leather. In the case of the lining of mouth and upper digestive tract this is only temporary as new mucosa are replenished, but in the meantime can calm inflamed or irritated surfaces. In the case of open wounds tannins can be a life-saver – when strong (as in the bark of broadleaved trees) they can seal a damaged surface. One group of tannins, the reddish-brown ‘condensed tannins’ are procyanidins, which can reduce inflammation and oxidative damage.
Bitter
Bitters are a very complex group of phytochemicals that stimulate the bitter receptors in the mouth. They were some of the most valuable remedies in ancient medicine. They were experienced as stimulating appetite and switching on a wide range of key digestive functions, including increasing bile clearance from the liver (as bile is a key factor in bowel health this can be translated into improving bowel functions and the microbiome). Many of these reputations are being supported by new research on the role of bitter receptors in the mouth and elsewhere round the body. Bitters were also seen as ‘cooling’ reducing the intensity of some fevers and inflammatory diseases.
Blue-purple colouring
Any fruits with a blue-purple colouring contain high levels of the polyphenols known as anthocyanins. These work 1) on the walls of small blood vessels, helping to maintain capillary structure to reduce a key stage in inflammation, and improving the microcirculation to the tissues; 2) to improve retinal function and vision; 3) to support connective tissue repair around the body.
Cooling
Traditional ‘cold’ or cooling’ remedies often contain bitter phytonutrients such a iridoids (gentian), sesiquterpenes (chamomile), anthraquinones (rhubarb root), mucilages (marshmallow), some alkaloids and flavonoids. They tend to influence the digestive system, liver and kidneys. Cooling herbs do just that; they diffuse, drain and clear heat from areas of inflammation, redness and irritation. Sweet, bitter and astringent herbs tend to be cooling.
Hot
Traditional ‘hot’ or ‘heating’ remedies, often containing spice ingredients like capsaicin, the gingerols (ginger), piperine (black or long pepper), curcumin (turmeric) or the sulfurous isothiocyanates from mustard, horseradich or wasabi, generate warmth when taken. In modern times this might translate as thermogenic and circulatory stimulant effects. There is evidence of improved tissue blood flow with such remedies: this would lead to a reduction in build-up of metabolites and tissue damage. Heating remedies were used to counter the impact of cold, reducing any symptoms made worse in the cold. .
Mucilaginous
Mucilages are complex carbohydrate based plant constituents with a slimy or ‘unctuous’ feel especially when chewed or macerated in water. Their effect is due simply to their physical coating exposed surfaces. From prehistory they were most often used as wound remedies for their soothing and healing effects on damaged tissues. Nowadays they are used more for these effects on the digestive lining, from the throat to the stomach, where they can relieve irritation and inflammation such as pharyngitis and gastritis. Some of the prominent mucilaginous remedies like slippery elm, aloe vera and the seaweeds can be used as physical buffers to reduce the harm and pain caused by reflux of excess stomach acid. Mucilages are also widely used to reduce dry coughing. Here the effect seems to be by reflex through embryonic nerve connections: reduced signals from the upper digestive wall appear to translate as reduced activity of airway muscles and increased activity of airway mucus cells. Some seed mucilages, such as in psyllium seed, flaxseed (linseed) or guar bean survive digestion to provide bulking laxative effects in the bowel. These can also reduce rate of absorption of sugar and cholesterol. .
New-mown hay aroma
The familiar country odour of haymaking, of drying grass and other plants, is largely produced by coumarins (originally isolated from tonka beans – in French coumarou) and widely used in perfumery. They are chemically categorised as benzopyrone lactones and are important phytochemicals, with strong antioxidant activity in the laboratory and likely effects in modulating inflammation. They were most often associated with the calming effect linked to their use in stuffing mattresses and pillows and plants, high In coumarins were commonly used for these properties.
Resinous
Resins are most familiar as tacky discharges from pine trees (and as the substance in amber, and rosin for violin bows). They were most valued however as the basis of ancient commodities like frankincense and myrrh (two of the three gifts of the Three Wise Men to the baby Jesus) and getting access to their source was one benefit to Solomon for marrying the Queen of Sheba (now Ethiopia). Resins were the original antiseptic remedies, ground and applied as powders or pastes to wounds or inflamed tissues, and were also used for mummification. With alcohol distillation it was found that they could be dissolved in 90% alcohol and in this form they remain a most powerful mouthwash and gargle, for infected sore throats and gum disease. They never attracted much early research interest because they permanently coat expensive glassware! For use in the mouth, gums and throat hey are best combined with concentrated licorice extracts to keep the resins in suspension and add extra soothing properties. It appears that they work both as local antiseptics and by stimulating white blood cell activity under the mucosal surface. They feel extremely effective!
Salty
The salty flavour is immediately distinctive. A grain dropped onto the tongue is instantly moistening and a sprinkle on food enkindles digestion. This easily recognisable flavour has its receptors right at the front of the tongue. The salty flavor creates moisture and heat, a sinking and heavy effect which is very grounding for the nervous system and encourages stability. People who are solid and reliable become known as ‘the salt of the earth'.
Sharpness
The sharp taste of some fruits, and almost all unripe fruits, as well as vinegar and fermented foods, is produced by weak acids (the taste is generated by H+ ions from acids stimulating the sour taste buds). Sour taste buds are hard-wired to generate immediate reflex responses elsewhere in the body. Anyone who likes the refreshing taste of lemon or other citrus in the morning will know that one reflex effect is increased saliva production. Other effects are subjective rather than confirmed by research but there is a consistent view that they include increased digestive activity and contraction of the gallbladder.
Sweet
In the days when most people never tasted sugar, ‘sweetness’ was associated with the taste of basic foods: that of cooked vegetables, cereals and meat. In other words sweet was the quality of nourishment, and ‘tonic’ remedies. Describing a remedy as sweet generally led to that remedy being used in convalescence or recovery from illness. Interestingly, the plant constituents most often found in classic tonics like licorice, ginseng are plant steroids including saponins, which also have a sweet taste.

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