Milk thistle is a medicinal plant popular for its extracts' benefits, known as silibinin or Legalon —a type of liver treatment. However, it also has important side effects to bear in mind.
Below we explain what this plant is, its uses, benefits, and side effects and contraindications that exist concerning its dosage.
Milk thistle, or Silybum marianum, is a plant used to treat liver disease and breastfeeding problems, among others. The herb's active ingredient, silymarin, is found in the mature seeds of the plant.
The plant has a long stem, green leaves with white spots and a flower head with pink to purple thorns. The Silybum marianum plant is native to Europe and grows wild in the United States and South America.
The leaves and stem of the milk thistle plant are edible and can be eaten raw, for example, in salads. The plant was cultivated as a vegetable in Europe until the end of the 19th century. Silymarin was first extracted by German scientists in the 1960s.
This plant's medicinal benefits have been known for more than 2 000 years. Written records show that Romans already used the plant in the 1st century to protect the liver.
It was also frequently used during the Middle Ages, when the medicinal properties of milk thistle seeds are first observed.
Nicholas Culpepper, a British herbalist, wrote about its benefits in treating liver and spleen diseases in the late 18th century, and by the end of the next century, records show that American doctors also prescribed it.
Silybum marianum is often prescribed as a treatment and prevention of liver disease, HIV, breastfeeding problems, gallbladder disorders, mushroom poisoning, and psoriasis.
Cardus marianus is believed to promote the growth of new liver cells and prevent toxins from penetrating through healthy liver cells by binding to cell membranes.
It is prescribed for cirrhosis and hepatitis, among others. Also, milk thistle may have a protective effect on the liver and is sometimes prescribed for patients taking medications that can cause liver damage (e.g., Thorazine, Haldol), or for those who are exposed to substances that are harmful to the liver, such as lead.
Silybum marianum is sometimes prescribed in HIV-positive cases to protect the liver from diseases such as hepatitis and from the hepatotoxic effects of other medications prescribed for the treatment of this virus.
This plant is often used in breastfeeding women to promote greater secretion of milk. Although the herb is considered safe for mothers, it should be purchased from a reliable source and prescribed by an herbalist, naturalist, or other health professionals that are familiar with its use.
The active chemical components of milk thistle, silymarin (a flavonoid complex) and silibinin, act as antioxidants. Research is currently underway on how these substances retard cell growth in some types of cancer.
Silybum marianum may prevent inflammation of the gallbladder ducts and eliminate jaundice. Its properties are very beneficial to biliary health.
Milk thistle is the only known antidote for death cap poisoning (Amanita phalloides). Ingestion of this deadly mushroom can destroy the liver by disrupting protein production in liver cells. Milk thistle neutralizes these toxins and protects the liver. It may also be useful in paracetamol overdose.
Because the liver neutralizes certain toxins associated with psoriasis, it is believed that milk thistle can prevent it by promoting proper liver function.
The antioxidant properties of this plant can have a healing effect on wounds and skin burns. Milk thistle is also used as a cosmetic agent to preserve skin tone and quality. More studies are needed to test its efficacy for these applications.
Milk thistle should always be obtained from a reliable source that complies with strict quality control procedures and industry-accepted good manufacturing practices.
It can be used during pregnancy and breastfeeding periods without any problem. However, there are no current long-term studies that confirm it. It is therefore advisable to notify a doctor of their use under these conditions.
This plant may cause nausea and diarrhea. It may also cause an allergic reaction in some people, particularly those with allergies to plants of the Asteraceae family (thistles, daisies, artichokes).
There is no evidence of any side effects other than those mentioned above as long as we take the recommended milk thistle dosage. However, people with chronic diseases should consult with their healthcare professionals before consuming it.
Ford-Martin, P., & Odle, T. G. (2005). Milk Thistle. In J. L. Longe (Ed.), The Gale Encyclopedia of Alternative Medicine (2nd ed., Vol. 3, pp. 1358-1360). Detroit, MI: Gale.