Milk thistle (Silybum marianum) is a famous herbal remedy with a reputation for improving liver function, but is that reputation justified?  Many people are kicking off January by going on detox diets which often involve taking milk thistle and other liver supporting or cleansing herbs.  But are they just wasting their money?

Well, not if the milk thistle extract they are taking is good quality.  Milk thistle has several active ingredients, primarily silymarin (which is made up of a mixture of flavonoid complexes); it also contains other flavanolignans.  These active ingredients have a very strong body of evidence showing them to be effective at preventing liver damage, improving liver function and promoting liver cell regeneration.


Milk thistle is a far more potent anti oxidant than vitamin E.  It has a powerful ability to protect the liver from damage due to this strong antioxidant action.  Free radicals and leukotrienes (pro inflammatory chemicals) are the main cause of liver cell damage and destruction.  Milk thistle neutralises these chemicals thereby preventing them from doing damage.

Alcohol and other liver toxins cause damage partly by depleting levels of glutathione in the liver.  Glutathione is an incredibly important antioxidant, which plays a key role in liver detoxification reactions and also promotes protein synthesis in the liver i.e. helps with liver regeneration.  Silymarin in milk thistle stops the depletion of glutathione in the liver in people who have consumed alcohol or other poisons; it also increases levels of glutathione in normal individuals.

Protection from harmful chemicals and drugs

Lots of animal studies have shown milk thistle to be very effective at minimising damage to the liver from a wide range harmful substances including alcohol, carbon tetrachloride, and the death cap mushroom which kills through liver poisoning.  When milk thistle extract was given to the mice before the toxins from death cap mushroom it was 100% effective at preventing toxicity.  (Mice given these toxins without milk thistle died from the poison).

In 2007 six members of the same family were extremely ill following accidental consumption of the death cap mushroom.  They were in danger of imminent liver failure.  An American doctor pushed hard to be allowed to administered milk thistle extract intravenously to the family. Everyone in the family except the 83 year old grandmother recovered.  This ground breaking treatment led to further human trials on milk thistle and it is now regularly used for liver poisoning by death cap mushrooms.

Liver regeneration

Milk thistle stimulates the liver to make new proteins and so stimulates the production of new liver cells to replace damaged ones.  Interestingly, it does not stimulate the production of malignant liver tissue.

Uses in human disease

Studies have shown milk thistle to be effective at improving detoxification reactions, improving bile flow and thereby helping with fat digestion and the prevention of gall stones, as well as being useful in the treatment of more serious liver diseases including:
Chronic hepatitis
Chemical or alcohol induced fatty liver

Emerging evidence suggests milk thistle may be of value not only in improving liver function for patients undergoing conventional cancer treatments but it may also in itself have cancer protecting and preventing action.  Some initial studies on children with leukaemia and men with prostate cancer showed very promising results.

Milk thistle for increasing milk in breast feeding mothers

Traditionally milk thistle seed was used as a remedy to improve milk production in nursing mothers and this use has been borne out by a recent study which involved nursing mothers taking a milk thistle extract for 63 days.  The mothers taking the extract had significantly greater improvements in breast milk production than the control group and no adverse side effects were reported.

How to identify a good quality milk thistle supplement

For milk thistle supplements to be effective they need to be made of milk thistle seed or fruit and not other parts of the milk thistle plant.  The fruit and seeds are the only part of the plant to contain significant concentrations of silymarin, the main active components.  The seeds are only produced by the plant once a year and so are more expensive to buy then other parts of the plant such as the leaves or stems which are constantly regenerating.  Some supplement makers chose to use these cheaper parts of the plant in their products.

To extract an effective quantity of silymarin you need to use large amounts of alcohol.  Many herbal tinctures of milk thistle use under the 60% alcohol concentration needed and therefore the resulting tincture will not have any health benefits.  If buying milk thistle tincture look for one made with dried material and an alcohol content of 60% or higher.

It is a good idea to look for milk thistle products which guarantee good levels of the active ingredients.  A standard dose of milk thistle is based on a silymarin content of 70-210mg taken three times daily.  For serious diseases, higher doses achieve better results i.e. 140mg-210mg of silymarin three times daily.  Alcohol based extracts are not recommended in liver disease as the dosages needed for these patients would involve them having to take in a relatively large amount of alcohol.

How safe is milk thistle?

Milk thistle preparations are widely used and a strong body of evidence suggests very low toxicity.  When taken in high doses it can cause looser stools, this is primarily due to its action on improving bile flow and secretion.

Article written by Ellie Holly