Milk thistle

Complementary treatment for liver problems

The Irish Times
Health Supplement, p. 13
5 August 2008

DOES IT WORK? Milk thistle and liver problems

Milk thistle is native to the Mediterranean region and has been used since ancient Greece to treat a variety of liver diseases. Several other names have been used for the plant, including holy thistle, St. Mary thistle and Our Lady’s thistle. These names come from the white veins on the plant’s leaves which were said to carry the milk of the Virgin Mary.

The plant grows to a height of up to ten feet. It produces bright, purple brush-like flowers which in the summer-time produce black seeds. These are used to make an extract containing a group of compounds that together are called silymarin. Most commercial extracts are standardised to contain 70-80 percent silymarin.

The extract is reported to protect the liver from poisons that cause liver damage. Alcohol is the most common cause of liver damage. More commonly, the extract is used to treat jaundice, cirrhosis of the liver (especially related to alcohol damage), hepatitis and other chronic liver diseases. Although a number of conventional treatments are used for liver diseases, none are as effective as one would hope, and some have significant adverse effects. For these reasons, much interest has focused on milk thistle as a complementary strategy for liver diseases.

Evidence from studies

Milk thistle has been consistently recommended by herbalists down through the centuries. Yet when medical researchers have examined the remedy, anything but consistency has been found. Last year a systematic review of controlled trials using milk thistle for cirrhosis or hepatitis B or C was published. Thirteen double-blind studies were found in which patients were randomly assigned to milk thistle or placebo. Some individual studies found benefits from milk thistle, but others found no benefits. Overall, the rate at which people died or had serious liver complications did not improve with milk thistle. However, most studies examined the effect of milk thistle on various lab tests. The results here were inconsistent, although some improvements were seen those taking milk thistle. The quality of these studies varied considerably. When only the highest quality studies were considered, milk thistle did not show any significant benefits.

The evidence for using milk thistle as an antidote to poisonous mushrooms is even more sparse. Its use here is based on laboratory studies showing that silymarin alters the liver cells to prevent toxins from entering. Several case reports have been published where milk thistle was used as a last resort in patients poisoned by the mushroom Amanita phalloides (also called ‘death cap’). Sometimes the extract was given orally, sometimes intravenously. Sometimes the patients recovered, sometimes they didn’t. In all cases numerous treatments were tried, making it impossible to know which ones (or which combinations) were beneficial. At the same time, a controlled trial for these poisonings would be very difficult to conduct in an ethically acceptable way.

Problematic aspects

One of the few consistent findings with milk thistle is a lack of adverse problems. Only a few minor problems have been reported, such as a laxative effect. Milk thistle belongs to the daisy plant family and may cause allergic reactions in those allergic to related plants and weeds.


Milk thistle is one of those herbal remedies with a long tradition of use but which medical science has not consistently confirmed. Decisions on whether or not to use these sorts of herbs are difficult. Given that studies have produced some supportive evidence, that it has few adverse effects and that conventional treatments can be limited, people with chronic liver problems may want to discuss milk thistle with their doctors. A trial period could be considered, with appropriate liver tests conducted to monitor any changes. Medical oversight is also important because the liver is involved in metabolising many medications which should also be closely monitored.

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