Common Names

St Mary's Thistle, Milk Thistle
Botanical Name
Silybum marianum L.
ASTERACEAE or COMPOSITAE ~ Sunflower family

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What is it?

Both the seeds and the leaves have been used in herbal medicine but most modern usage revolves around the approximately 7mm long grey seeds and the extracts made from them. St Mary’s thistle is a familiar prickly plant that lives for 2 years and grows to a little less than a meter in height.




How has it been used?

St Mary’s thistle has been famous as a liver herb for thousands of years. It has been widely used for liver and gallbladder diseases including hepatitis, cirrhosis, gallstones and jaundice.

T. Bartram states that 'St Mary’s thistle is a cholagogue for promoting the flow of bile up to 60% more in liver disorders' and calls it a 'Liver protector, producing new cells in place of the old'.

S. Mills calls for its use 'whenever alcohol, drug or dietary abuse, or exposure to chemical pollution threatens normal liver function'.

German doctor Rudolph Weiss devotes several pages of his seminal work to St Mary's thistle including describing in great detail how high doses of it can be used to reduce the mortality to 0% from such fatal poisonings as from the Amanita mushroom.


Science on St Mary's

Modern research shows that St Mary’s thistle has a truly remarkable ability to both regenerate damaged liver cells and to protect them from poisons.

St Mary’s thistle has been exceptionally well studied in modern times. The main active ingredient of St Marys is an extract called Silymarin that in turn contains an array of substances called flavanolignans such as silychristin, silybin and silydianin. Almost all the research has been done with concentrates of Silymarin so when we extrapolate out from these studies into clinical practice we have to be careful to ensure the dosages are adequate to what has been achieved in the trials (more info about dosage below).

A few highlights of the research on St Mary's thistle are summarised here:
~ St Mary’s thistle extract, given both before and after surgery, stopped the rise of liver enzymes that otherwise always happen due to the toxic effects of general anaesthesia (Fintelmann V. Med Klin 1973;68(24):809-815)

~ In double blind and randomised clinical trials St Mary’s thistle extract significantly increased survival time of people with liver cirrhosis from varying causes but chiefly alcoholic cirrhosis (Velussi M, Cernigoi AM, De Monte A et al. J Hepatol 1997;26(4):871-879)

~ St Mary’s thistle extract improved the biochemical and functional health of the livers of patients with acute and subacute liver disease in a double-blind, placebo-controlled clinical trial (Ravanelli DV, Haase W. Prak Arzt 1976;30(346):354-367)

~ In a randomized, double-blind, placebo-controlled study St Mary’s thistle extract significantly reduced the toxic effects to the liver of psychotropic drug treatments (Palasciano G, Portincasa P, Palmier V et al. Curr Ther Res Clin Exp 1994;55(5):537-545)

~ St Mary’s thistle extract was shown in a number of uncontrolled trials on patients with toxic liver damage from various origins to significantly reduce liver enzymes, improve platelet counts, reduce general nausea, discomfort and skin itching (Szilard S, Szentgyorgyi D, Demeter I. Acta Med Hung 1988;45(2):249-256)

~ In laboratory studies, St Mary’s thistle extract showed that it protected the liver and helped repair the liver from damage from an array of toxic substances including heavy metals, irradiation, death cap mushroom, viruses and other chemicals (Hakova H. Misurova E. Radiats Biol Radioecol 1996;36(3):365-370)

The authors, titles and the 'where-and-when' published of nearly 200 further studies and articles on St Mary's thistle are listed in a PDF found here

Safety of St Mary's

Being it is a member of the great medicinal Compositae family there is a tiny chance of allergy but otherwise St Mary’s thistle is exceptionally safe to take whilst pregnant or breastfeeding and it may be used with much benefit by people of all ages.


Personal experiences

I use a great deal of St Mary’s thistle in my practice. The kinds of people I use St Mary’s thistle for typically show some indicators that their liver needs some support. This may appear in such signs as poor skin, a furry tongue, excess debris in their blood analysis, a heavy or languid pulse, food allergies or disturbed digestive function.

St Mary's is also the first 'go-to' medicine I think of when people are suffering from toxic effects from prescription drugs but still need to be on them.

There are compelling arguments that much of the reason for the increases in cancer and allergy-based illness in our society are due to the heavy toxic load that we now carry as a collective. I don’t think anyone can deny that we are surrounded by more pollution and chemical additives than at any other time in history and it is clearly the liver that bears the brunt of this onslaught of toxicity.

Given all this it is truly a remarkable, proven fact that in St Mary’s thistle we have a herb that both protects the liver from damage whilst at the same time helping it to regenerate itself.

It is very important to understand that St Mary's thistle is a herb that needs to be taken in adequate quantity for the active ingredients to work. Many commercial preparations of St Marys are substandard and would require you to take much more than the recommended dosage on the label to get the real benefits of this herb. Getting your St Marys from a reputable herbalist should ensure you get the right stuff but as another option I've also had excellent results with a very cheap and simple way to take St Mary's thistle as a ground slurry as described below

St Mary's thistle slurry

~ Ingredients:
1 heaped dessertspoon of freshly ground St Mary's thistle seeds
enough water to make into an easily drunk 'slurry'

~ Recipe:
Take one heaped dessertspoon of St Mary’s thistle seeds and grind them as fine as you can in any kind of small kitchen blender. Mix the powdered seeds into water and drink it all down. The ground St Mary's seeds are not bad tasting at all, just a slightly nutty flavour.

~ Dosage:
If you want to get a lot of St Marys into a person who has a really sick liver or who has been poisoned by something then this slurry is ideal to use 2 times a day for up to a week. At that point, if there are ongoing concerns that still need treatment, taking the slurry once a day should be sufficient.

1 heaped dessertspoon of the ground seeds equals close to a massive 20grams of St Mary's thistle so it really is a tremendous way to harness the great power of this herb when it is particularly needed.

An excellent experiment to see if the reason that you are feeling run-down, tired, grumpy etc is that you are simply a bit 'liverish' is to take the above slurry once a day for a week. If your liver needed a boost you will almost certainly feel quite remarkably better for the process!

St Mary's thistle combines perfectly with Dandelion root to gently cleanse the liver, with Golden Seal to activate liver detoxification pathways and Celandine as a particularly potent combination when the need to remedy liver congestion is especially great.


Constitutional note

Much of the information here about the traditional uses of St Mary's Thistle is consistent with the model of thinking whereby one may treat problem A with plant B. There is value in this approach, especially in how it helps us pass on useful knowledge to one another, but it falls short in one vital area; and that is that people are not all cut from the same cloth! Something that works brilliantly for one person may do less for another, why is this?

The reason is that people vary in their constitutions as to whether they are either hotter or cooler and, at the same time, either dryer or damper. This interesting and useful subject is introduced further here

There is an old wisdom in treating the person first and the condition second and in this light St Mary's thistle can particularly offer its benefits when a cleansing action is needed in the 'cycle of healing', more about this here

Excerpt from Felter & Lloyd's Kings Dispensatory from 1898

Congestive conditions of the liver are those most benefited by St Mary's thistle. To some extent the whole venous apparatus is influenced by this drug, giving power to the veins, and preventing varicoses and other dilatations.

Dull, aching, splenic pain passing up under the left scapula, and associated with pronounced general debility and despondency is the indication for its use. It controls splenic pain even where no enlargement can be detected, and it is the remedy for hypertrophy of the spleen when non-malarial in character.

Congestion of the liver, spleen and kidneys is relieved by its use. Bilious states, with stitches in the side and pain in the abdomen, hard and tender right hypochondrium, gall stones, jaundice, hepatic pain and swelling, vomiting of pregnancy, and leucocythemia, are conditions in which it is highly useful.

Please understand that I cannot advise you, including on products or dosage, without seeing you in person in my clinic but for ideas on how you might find a good herbalist in your area read here

This living 'book' is my labour of love so, wherever you are, I wish you peace & good health!



© 2011 R.J.Whelan Ltd