About Milk Thistle
Milk thistle (silymarin) is a dietary supplement traditionally used to treat and prevent damage to the liver. There has been some research of mixed quality to assess the potential of Milk Thistle in treating and preventing liver damage from alcohol and from other causes which have shown a very positive potential benefit. However it is clear more robust, placebo controlled clinical studies involving human volunteers are needed.
What is Milk Thistle or Silybum marianum?
Milk Thistle or Silybum marianum as it is known in more technical botanical circles, is an annual or biannual plant of the Asteraceae family. This fairly typical thistle is a thorny plant, has red to purple flowers and shiny pale green leaves with white veins. The medical parts of the plant are the ripe seeds not the leaves.
The flower heads are 4 to 12 cm long and wide, of red-purple colour. They flower from June to August in the North or December to February in the Southern Hemisphere (Summer through Autumn).
Thistle is an old English word and Milk Thistle gets its name from the milky sap that comes out of the leaves when they are broken. The leaves also have unique white markings that, according to legend, were the Virgin Mary’s milk. Thistles describe a a large family of plants occurring in Europe and Asia under the botanical groups Carduus, Carlina, Onopordon and Carbenia, or Cnicus.
Many people get confused with all the different, very similar sounding names. Milk Thistle is often called Blessed Milk Thistle, Marian Thistle, Mary Thistle, Saint Mary's Thistle, Mediterranean milk thistle, Variegated Thistle and Scotch thistle. However, Milk thistle should not be confused with Holy or Blessed Thistle (Cnicus benedictus) and the Scotch Thistle (Onopordum acanthium), it is a different species with different medicinal properties. Whereas Holy Thistle cannot be eaten, Scotch Thistle and Milk Thistle are edible and used by foragers as ‘bush food’.
The Silybum species as a whole is native to the Mediterranean regions of Europe, North Africa, and the Middle East; and the most widespread species is Silybum marianum. The plants in Silybum group include:
- Silybum eburneum Coss. & Dur., known as the Silver Milk Thistle, Elephant Thistle, or Ivory Thistle (Algeria, Morocco, Tunisia, Spain)
- Silybum eburneum Coss. & Dur. var. hispanicum
- Silybum marianum (L.) Gaertner
Where does Milk Thistle grow and naturally found?
Originally a native of Southern Europe, Silybum marianum was probably first found around the coast of southeast England (perhaps brought by the Romans) or from the mountains of the Mediterranean region. It is now found throughout the world including the United States, North, Australia and New Zealand where it is considered a weed.
Milk Thistle is grown by the pharmaceutical and herbal supplements industry in areas such as Waldviertel in Austria, Germany (Milk Thistle is called Mariendistel in German), Hungary, Poland, Argentina and China.
In Europe it is sown yearly in March–April. The harvest in two steps (cutting and threshing) takes place in August, about 2–3 weeks after the flowering.
Milk Thistle extract and its chemistry
Traditional milk thistle extract is made from the seeds, which contain approximately 4–6% silymarin. The extract consists of about 65–80% silymarin (a flavonolignan complex) and 20–35% fatty acids, including linoleic acid.
Silymarin is a complex mixture of polyphenolic molecules, including seven closely related flavonolignans (silybin A, silybin B, isosilybin A, isosilybin B, silychristin, isosilychristin, silydianin) and one flavonoid (taxifolin).
Origins of Medicinal use of Milk Thistle and use as Liver Tonics and Liver Detoxifiers
Silymarin marianum has been used by humans probably for thousands of years for its medicinal effects. The liver protective effects, for example, were known and written about in ancient times in Roman and Greek texts. It is possible that as a whole the plant has anti-bacterial, anti-fungal, anti-viral and anti-parasitic action.
The liver has a wide range of functions in the human body and we cannot live without it functioning properly. Lobules are the functional units of the liver and each lobule is made up of millions of hepatic cells (hepatocytes) which are the basic metabolic cells. It is pivotal in the detoxification of various metabolic by products of food, protein synthesis, and the production of biochemicals necessary for digestion. It also plays a role in metabolism, regulation of glycogen (energy related) storage, decomposition of red blood cells and hormone production. So your liver is a pretty important organ!
Therefore it is not surprising that any drug which helps the liver to cleanse more effectively can be useful in treating liver diseases such as liver cirrhosis, chronic hepatitis (liver inflammation) and jaundice. Cirrhosis is a condition in which the liver does not function properly due to long-term damage with scarring. Cirrhosis is most commonly caused by alcohol or the viruses hepatitis B and hepatitis C. Jaundice is the medical term that describes yellowing of the skin and eyes caused when there is too much bilirubin in the body. Bilirubin is a yellow pigment that is formed by the breakdown of dead red blood cells in the liver. Normally, the liver gets rid of bilirubin along with old red blood cells.
For many centuries extracts of milk thistle were used as "liver tonics" used to treat alcohol and toxin related liver damage. The plant was even used for the prevention of severe liver damage from the accidental eating of Death Cap mushroom (Amanita phalloides) in days gone by .
The plant also appears to have some ability to remove toxins. The physician Wiliam Westmacott, writing in 1694 in "The education of a puritan Country Physician" said of Milk Thistle: 'It is a Friend to the Liver and Blood” .
Traditionally it was has also been used as a hangover cure (and some swear by its effectivensss here)and is still used in traditional Chinese medicine to “clear heat and relieve toxic material”, to soothe the liver and to promote bile flow.
These anecdotal medicinal properties led to research being conducted by German scientists beginning in the 1950's to assess its active chemical, pharmacological, and safety leading to the commercial growing of the plant for pharmaceutical purposes.
Dosage of Milk Thistle
In clinical trials silymarin has typically been administered in amounts ranging from 420–480 mg per day in two to three divided doses. However higher doses have been studied, such as 600 mg daily in the treatment of type II diabetes and 600 or 1200 mg daily in patients chronically infected with hepatitis C virus.
An optimal dosage for milk thistle preparations has not been established.
Clinical efficacy of Milk Thistle - does Milk Thistle work and is it safe? Does it harm the liver?
At recommended doses:
- Does Milk Thistle work - Yes
- Is Milk Thistle safe - Yes
- Does Milk Thistle harm the liver - No
- Does Milk Thistle have harmful side effects - No
A thorough review of the literature on milk thistle current to the year 2000 can be found at Milk Thistle: Effects on Liver Disease and Cirrhosis and Clinical Adverse Effects whose link is located below:
This review finds that the evidence to date is strongly suggestive that milk thistle helps heal or cleanse the liver, although studies to date are not yet fully conclusive. However, Milk Thistle is very likely not to harm the liver.
A more recent review of the literature can be found in Saller (2008) "An updated systematic review with meta-analysis for the clinical evidence of silymarin" which concluded, "Based on the available clinical evidence it can be concluded - concerning possible risks /probable benefits - that it is reasonable to employ silymarin as a supportive element in the therapy of Amanita phalloides poisoning but also (alcoholic and grade Child 'A') liver cirrhosis. A consistent research programme, consolidating existing evidence and exploring new potential uses,would be very welcome."
Side effects of Milk Thistle
On the available evidence, which is not exhaustive, Milk Thistle (Silymarin) is likely to be safe for most adults. However, it sometimes causes minor side effects such as a laxative effect. Other less common side effects are nausea, diarrhoea, indigestion, intestinal gas, bloating, fullness or pain, and loss of appetite.
Special Precautions & Warnings:
Pregnancy and breast-feeding: Not enough is known about the use of milk thistle during pregnancy and breast-feeding. Stay on the safe side and avoid use.
Allergy to ragweed and related plants: Milk thistle may cause an allergic reaction in people who are sensitive to the Asteraceae/Compositae plant family. Members of this family include ragweed, chrysanthemums, marigolds, daisies, and many others. If you have allergies, be sure to check with your doctor or pharmacist before taking milk thistle.
Hormone-sensitive conditions such as breast cancer, uterine cancer, ovarian cancer, endometriosis, or uterine fibroids: Extracts from Milk Thistle plant might act like oestrogen. If you have any condition that might be made worse by exposure to estrogen, don’t use these extracts. In contrast, the more commonly used milk thistle seed extracts do not seem to act like oestrogen.
Milk Thistle Products
You can buy Milk Thistle in the form of tablets, capsules and drops either as a single ingredient in different strengths or as a combination with other liver cleansing herbs. Popular brands include Natures Aid, Vogel, Solgar and Schwabe.
Should I take Milk Thistle supplements regularly?
The jury is still out on whether it really works, but Milk Thistle appears to have low toxicity and studies are suggestive of a positive effect on the liver and it having a protective effect against excessive drinking of alcohol. The benefits therefore seem to outweigh any very limited risks. The editor of the Fermented Grape uses Milk Thistle personally, but do your own research before taking this supplement and if in doubt talk to your doctor. They could be associated with a placebo effect, but the evidence suggests not.
Using Dandelion root with Milk Thistle
In addition to Milk Thistle other herbs and vitamins are said to help the liver cleanse itself. Antioxidant vitamins such as C, E, and beta-carotene; minerals such as zinc and selenium; B-vitamins that aid alcohol metabolism. Dandelion root and schizandra are traditionally held to have liver cleansing actions.
About the author
This article is written by Richard Norton, trained in Pharmacy and working in the healthcare industry since 1994. He has no affiliation with any Milk Thistle or herbal supplements company and views are his own, not his employer, based on the available evidence.
Lawrence V, Jacobs B, Dennehy C, et al. (2000) Milk thistle: effects on liver disease and cirrhosis and clinical adverse effects. Evidence Report/Technology Assessment No. 21. AHRQ Publication No. 01-E025. Rockville, MD.