Milk thistle, also known as Silybum marianum or Carduus marianus, is a plant that is native to Europe’s Mediterranean region.1 It was introduced into North America by the colonists. It can now be found in California and the eastern United States. Milk thistle was traditionally used to treat liver and gallbladder diseases.1 Currently, milk thistle is used as a dietary supplement for hepatitis, cirrhosis, jaundice, and indigestion.1,2
What are liver and biliary tract diseases?
Liver diseases are the diseases that affect the liver. They can be caused by virus, drugs, and excessive alcohol consumption.3,4 The most common liver diseases are hepatitis, fatty liver disease, cirrhosis, liver cancer, and liver failure. Symptoms of liver diseases include jaundice (yellowing of the skin and eyes), nausea, vomiting, fatigue, abdominal pain, dark-colored urine, and light-colored stool.3,4 Liver function tests such as albumin, bilirubin, alanine aminotransferase (ALT), and aspartate aminotransferase (AST) may be performed to help diagnose liver diseases.3 Prescription medications used to treat liver diseases include antivirals, steroids, blood pressure medications.4 Some people also take vitamins and supplements to boost liver health.4
Biliary tract diseases are the diseases that affect the bile ducts and gallbladder.5 Bile is a fluid produced by the liver and stored in the gallbladder. Symptoms of biliary tract diseases include jaundice, abdominal pain, loss of appetite, fatigue, light brown urine, and greasy or clay-colored stools.5 Tests that are commonly done to diagnose biliary tract diseases are liver function tests, liver biopsy, blood tests, ultrasound, and MRI.5 Treatments for biliary tract diseases include medications that increase the flow of bile from the liver and antibiotics.5
How does milk thistle improve symptoms of liver and biliary tract diseases?
The active compound in milk thistle is called silymarin.2 Silymarin is thought to be responsible for stabilizing cellular membranes, stimulating detoxification pathways, and stimulating the liver tissue regeneration.2
Not too many studies have been conducted to assess whether milk thistle is beneficial in patients with liver and biliary tract diseases. A 2009 randomized controlled trial assessed the safety and efficacy of silymarin on symptoms, signs, and biomarkers of acute hepatitis.6 The participants were given either silymarin 140 mg daily for 4 weeks or placebo for 4 weeks. Biliary retention symptoms (dark urine, jaundice, scleral icterus) resolved quicker in patients who were given silymarin, compared to those who were given placebo. However, the liver function tests (bilirubin, alanine aminotransferase (ALT), and aspartate aminotransferase (AST)) were similar in silymarin and placebo groups.
A 2012 randomized controlled trial investigated effect of silymarin on liver disease in patients with chronic hepatitis C virus (HCV) infection who were not successfully treated with interferon-based therapy.7 The participants were randomly assigned to silymarin 420 mg three times daily for 24 weeks, silymarin 700 mg three times daily for 24 weeks, or placebo for 24 weeks. There was no significant difference across the three groups in liver function tests and quality of life.
Moreover, a 2017 systematic review with meta-analysis looked at 23 studies on the effect of silymarin in patients with liver disease.8 The meta-analysis concluded that silymarin did not significantly improve the liver functions of the patients with liver disease.
How do you take milk thistle?
Milk thistle supplement is made from the seed-like fruit of milk thistle, which contains silymarin.2 The major component of silymarin is silybin. Most milk thistle supplements in the market are standardized according to the silybin content.2,9 The supplement is available as capsules, tablets, powder, and liquid extract.2 Milk thistle is not approved as a drug by the Food and Drug Administration (FDA). It can be tough to figure out how much milk thistle to take since there are no official recommended dosages. It is recommended to start with a low dosage and increase slowly until the desired effect is reached. Before using milk thistle, have a discussion with your doctor to make sure it is appropriate to use.
Safety of milk thistle
Milk thistle is generally well tolerated.1,2 Most common side effects are diarrhea and upset stomach.2,10 Other less common side effects include nausea, bloating, flatulence, and indigestion.11 The safety of milk thistle during pregnancy and lactation has not been vigorously studied.1 Milk thistle may mimic the effect of estrogen.11 So, it should be avoided in women who have endometriosis, breast cancer, uterine cancer, and ovarian cancer.
Milk thistle is not known to have serious interactions with any medication. Milk thistle has moderate interaction with diabetes medications.11 It can lower blood glucose levels, increasing the risk of hypoglycemia. Milk thistle binds to estrogen receptor, so it may interfere with estrogen therapy.11 In addition, milk thistle may slow blood clotting.11 Therefore, taking milk thistle and warfarin at the same time may increase the risk of bleeding.
Milk thistle is currently used as a dietary supplement for liver and biliary tract disorders. Silymarin, the active component of milk thistle, is thought to stabilize cellular membranes, activate detoxification pathways, and stimulate the regeneration of liver tissues. Study findings concluded that milk thistle did not improve symptoms of liver and biliary tract diseases. If you are planning to use milk thistle, please consult your doctor to make sure that it is safe and appropriate for you.
- “Milk Thistle.” National Center for Complementary and Integrative Health. https://www.nccih.nih.gov/health/milk-thistle. Aug. 2020. Accessed Oct. 21, 2020.
- “Milk Thistle (PDQ) – Health Professional Version.” National Cancer Institute. https://www.cancer.gov/about-cancer/treatment/cam/hp/milk-thistle-pdq. Oct. 29, 2019. Accessed Oct. 21, 2020.
- “Liver Diseases: What You Should Know.” WebMD. https://www.webmd.com/hepatitis/liver-and-hepatic-diseases. Accessed Oct. 21, 2020.
- “Liver Diseases 101.” Healthline. https://www.healthline.com/health/liver-diseases. March 21, 2019. Accessed Oct. 21, 2020.
- “Biliary Disease.” George Washington University Hospital. https://www.gwhospital.com/conditions-services/digestive-disorder-center/biliary-disease. Accessed Oct. 21, 2020.
- El-Kamary, Samer S et al. “A randomized controlled trial to assess the safety and efficacy of silymarin on symptoms, signs and biomarkers of acute hepatitis.” Phytomedicine : international journal of phytotherapy and phytopharmacology 16,5 (2009): 391-400. doi:10.1016/j.phymed.2009.02.002
- Fried, Michael W et al. “Effect of silymarin (milk thistle) on liver disease in patients with chronic hepatitis C unsuccessfully treated with interferon therapy: a randomized controlled trial.” JAMA 308,3 (2012): 274-82. doi:10.1001/jama.2012.8265
- de Avelar, Camila Ribeiro et al. “Effect of silymarin on biochemical indicators in patients with liver disease: Systematic review with meta-analysis.” World journal of gastroenterology 23,27 (2017): 5004-5017. doi:10.3748/wjg.v23.i27.5004
- “Milk thistle.” Mayo Clinic. https://www.mayoclinic.org/drugs-supplements-milk-thistle/art-20362885. Oct. 14, 2017. Accessed Oct. 21, 2020.
- “Milk Thistle: Benefits and Side Effects.” WebMD. https://www.webmd.com/digestive-disorders/milk-thistle-benefits-and-side-effects#1. Accessed Oct. 21, 2020.
- “Milk Thistle.” Natural Medicines. https://naturalmedicines-therapeuticresearch-com.proxy.hsl.ucdenver.edu/databases/food,-herbs-supplements/professional.aspx?productid=138. Accessed Oct. 21, 2020.