What is Milk Thistle Used For? A Guide To The Herb's Health Benefits

Quick Health Scoop

• Milk thistle is an herb that contains silymarin, which is believed to have antioxidant properties
• In recent years, milk thistle has become more popular as an herbal remedy
• Though generally considered safe to take, milk thistle has benefits and side effects
• Preliminary research shows promise of milk thistle for liver health, but more conclusive research is needed

Did you know that people have been using milk thistle as a medicinal herb for at least 2000 years?^†,1 Also known as Silybum marianum, milk thistle has become more popular as an herbal remedy, often taken as a milk thistle supplement. But you might be wondering exactly what milk thistle is as well as milk thistle uses, health benefits and side effects.

What Is Milk Thistle?

Here’s a quick science and geography lesson on milk thistle to provide some context on this popular herb. Native to the Mediterranean region, milk thistle can now be found throughout the eastern United States, California, South America, Africa, Australia, and Asia.² 

This flowering, prickly herb is in the same “plant family” as daisies and ragweed and, at maturity, grows between 2 feet to 6½ feet tall. With its distinctive reddish-purple flowers and white veins, milk thistle contains an active ingredient called silymarin, which is extracted from the herb’s seeds and is believed to have antioxidant properties.^†,3

What Is Milk Thistle Used For?

For centuries, people around the world have primarily relied on milk thistle benefits when practicing traditional medicine. According to the World Health Organization, traditional medicine is “the sum total of the knowledge, skill, and practices based on the theories, beliefs, and experiences indigenous to different cultures, whether explicable or not, used in the maintenance of health as well as in the prevention, diagnosis, improvement or treatment of physical and mental illness.”⁴

What is milk thistle used for? In traditional medicine, milk thistle is good for supporting a healthy liver and gallbladder.^{†, 2}

What does milk thistle do to the liver? As the most well-researched plant in supporting liver health, milk thistle’s superpower lies in its active ingredient called silymarin, noted above. Because silymarin acts as an antioxidant by reducing damaging free radicals in the body, it can help support healthy liver function.^{†, 6} 

What Are the Side Effects and Interactions of Milk Thistle?

If you’re worried about milk thistle side effects, it is generally considered safe to take for most people. However, it may cause some side effects, especially for people with certain health conditions.

Talk to your doctor before taking a milk thistle supplement, especially if you have any health concerns or medical condition. Milk thistle can trigger allergic reactions, similar to other plants in the same family, such as chrysanthemums, daisies, marigolds, ragweed.⁵Milk thistle may also cause stomach upset.² 

What can you not take with milk thistle? If you regularly take any medications, talk to your doctor before taking milk thistle. Why? Because it may interact with the following drugs:³

• Cytochrome P450 2C9 (CYP2C9) substrates
• Diabetes medications
• Osteoporosis medication: Raloxifene (Evista)
• Hepatitis C medication: Simeprevir
• Immunosuppressant: Sirolimus (Rapamune)

Tips for Taking Milk Thistle

What is the best way to consume milk thistle? This herb is commonly taken as a milk thistle supplement in the form of capsules, extracts, or tinctures. It can also be ingested as tea, but its therapeutic compounds are not readily soluble in water, which is why tea offers less value.⁷

Wondering how much milk thistle you should take a day? Research suggests that a safe dosage range is 175 mg extract standardized to ≥80% silimarin, two to three times daily.8 Check with your doctor to get the right dosage for your individual circumstances. 

The Bottom Line

Historically, milk thistle has been used in traditional medicine to support a healthy liver. ^† Because the herb’s active ingredient (silymarin) acts as an antioxidant, milk thistle supports healthy liver function. Preliminary research shows promise as a complementary therapy for various health conditions, but more conclusive research is needed to confirm milk thistle’s health benefits. Of course, you should always check with your primary care physician before taking any supplements—especially if you are pregnant or breastfeeding or taking other medications.

Continue to check back on the Nature Made blog for the latest science-backed articles to help you take ownership of your health.

This information is only for educational purposes and is not medical advice or intended as a recommendation of any specific products. Consult your health care provider for more information.

† These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure, or prevent any disease.

References 

1. Agriculture and Natural Resources, University of California. “Blessed Milkthistle.” 2016. Accessed on: March 15, 2021. http://ipm.ucanr.edu/PMG/WEEDS/milkthistle.html

2. National Center for Complementary and Integrative Health. “Milk Thistle.” August 2020. Accessed on: March 15, 2021. https://www.nccih.nih.gov/health/milk-thistle

3. Mayo Clinic. “Milk Thistle.” November 19, 2020. Accessed on: March 16, 2021. https://www.mayoclinic.org/drugs-supplements-milk-thistle/art-20362885

4. World Health Organization. “Traditional, Complementary and Integrative Medicine.” 2021. Accessed on: March 16, 2021. https://www.who.int/health-topics/traditional-complementary-and-integrative-medicine#tab=tab_1

5. University of Rochester Medical Center. “Milk Thistle.” 2021. Accessed on: March 16, 2021. https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=19&contentid=MilkThistle

6. Medical News Today. “Ten health benefits of milk thistle.” December 20, 2017. Accessed on: March 16, 2021. https://www.medicalnewstoday.com/articles/320362#ten-health-benefits-of-milk-thistle

7. Esposito T, Sansone F, Russo P, et al. A Water-Soluble Microencapsulated Milk Thistle Extract as Active Ingredient for Dermal Formulations. Molecules. 2019;24(8):1547. Published 2019 Apr 19. doi:10.3390/molecules24081547

8. Huntington College of Health Sciences. “Smart Supplementation: Milk Thistle.” 2009. Accessed on: March 16, 2021.