Here's an overview of its characteristics, traditional uses, primary compounds, and relevant scientific research.
What is Milk Thistle?
Scientifically known as Silybum marianum, Milk Thistle is a tall, prickly plant with distinctive purple flowers and white veins. It belongs to the Asteraceae (daisy) family and is native to the Mediterranean region but is now widely cultivated worldwide.
Milk Thistle contains a group of flavonoids collectively known as silymarin, which includes silybin, silychristin, and silydianin. Silymarin is considered the primary active compound responsible for Milk Thistle's therapeutic effects.
Traditional Uses
Milk Thistle has been used in traditional medicine systems around the world for centuries, particularly in Western herbalism.
In European herbalism, Milk Thistle was traditionally used to treat liver disorders, jaundice, and gallbladder issues.
In Ayurvedic medicine, Milk Thistle is used as a liver tonic and to support digestion and detoxification.
Health Benefits of Milk Thistle
1. Liver Support: Milk Thistle is best known for its hepatoprotective properties, supporting liver health and function. It has been used traditionally to treat liver disorders such as hepatitis, cirrhosis, and fatty liver disease. It is used to promote liver detoxification, and protect the liver from damage caused by toxins, alcohol, and other substances.
2. Antioxidant Effects: Milk Thistle contains flavonoids, including silymarin, which have antioxidant properties. These compounds help protect liver cells from oxidative damage caused by free radicals. They also help neutralize harmful free radicals, reducing oxidative stress and inflammation throughout the body.
3. Anti-inflammatory Properties: Silymarin, the active compound in Milk Thistle, exhibits anti-inflammatory effects, which may help reduce inflammation in the liver and benefit conditions such as arthritis, inflammatory bowel disease, and skin inflammation.
4. Cholesterol Management: Some research suggests that Milk Thistle may help lower cholesterol levels, which can benefit cardiovascular health.
Following is some notable research on milk thistle.
HIV-1 inhibited in human cells
Researchers from the University of Washington’s Department of Laboratory Medicine have found that a Silymarin extract from the Milk thistle herb inhibits the growth of the Human immunodeficiency virus-1 (HIV-1) among human cells.
The research comes as the HIV-1 virus, and its subsequent development into AIDS – acquired immunodeficiency syndrome – has continued to spread worldwide in epidemic-like proportions.
Currently about 40 million people around the world are infected with the HIV virus. At least 70% of this number live in Africa.
The research utilized the HeLa cell line. This is a human cell line that has been used for decades in countless other human cell studies, including polio research, cancer research and AIDS research.
Multiple cultures of the cells were either bathed in dilutions of Silymarin or not, at varying concentrations, using triplicate parallel testing. The cell dilutions were then incubated with two different strains of the HIV-1 virus.
After different incubation periods, including 48-hours, two-days, and up to two weeks, the cell cultures were analyzed and cross-analyzed for HIV-1 infection and growth rates. The multiple assays were conducted using two independent analysis groups, and then the test results were compared.
HIV-1 replication studies were also done using PBMC (immune) cells to test HIV’s replication within the immune system. Here again cells were tested with and without the Silymarin extract solution. T-cell proliferation and cytokine production were also tested.
Higher silymarin doses inhibit HIV more
At higher doses ,the Silymarin complex inhibited the two strains of HIV-1 viruses by 97% and 80%. The 97% inhibition took place with the earliest and most found form of HIV-1, the LAI strain. Silymarin also suppressed the replication of LAI HIV-1 as tested with immune cells. Silymarin also blocked the LAI and BAL HIV-1 strains from further infecting cells during the incubation period.
Silymarin’s inhibition of the LAI HIV-1 infection among PBMC immune cells lasted for over two weeks in the cell cultures.
The Milk thistle extract also inhibited the production of T-cells and B-cells, unrelated to any cell death or toxicity.
In their discussion, the researchers stated:
“This study shows for the first time that a mixture of two compounds derived from silymarin and formulated for intravenous dosing inhibited HIV-1 infection in multiple cell types including human PBMCs, CEM cells, and TZM-bl cells. SIL’s anti-HIV effects were seen against four viruses.”
Their Silimarin solution was produced using two key compounds, silybin A and silybin B. These were converted to disodium disuccinyl silybin A and disodium disuccinyl silybin B to aid their dilution into the solutions. The body performs a similar process as it ‘chelates’ compounds to allow for their absorption into the body.
Because Silymarin is not water-soluble, it is relatively difficult to fully absorb, and infusions of the Milk thistle herb – tea, in other words – provide little if any medicinal compound absorption.
The researchers also noted that due to Silymarin’s ability to slow the production of T-cells, this could also help prevent the depletion of immune function – which typically occurs at least partially because HIV infection will deplete the body’s T-cells.
The researchers, in fact, saw multiple mechanisms of action among Silymarin with respect to inhibiting, slowing and preventing HIV infections. They stated: “Cumulatively, the data presented in this report suggest that SIL inhibited viruses by multiple inhibitory mechanisms that target the cell and reduce the activation status/potential.”
Silymarin slows liver inflammation
They also noted that Silymarin’s ability to slow liver inflammation associated with the Hepatitis-C virus – which is thought to infect nearly a third of those in Western countries infected with HIV – may also offer a therapeutic route for those who are co-infected with HIV and HCV.
The groundbreaking research was led by Stephen J. Polyak, Ph.D., a professor in the University of Washington’s Department of Laboratory Medicine and Department of Microbiology. He was the recipient of the American Liver Foundation’s Liver Scholar Award, and his research has been supported by the National Institutes of Health.
Slymarin derivative also inhibits HIV
A 2014 study from the University of Washington tested silibinin derived from milk thistle, along with legalon-SIL, a derivative of silibinin. The researchers found that when T-cells are dosed with the SIL, the T-cells became immune to the entry of the HIV-1 virus.
The bottom line is that milk thistle contains multiple compounds that will inhibit the infection of HIV virus. Since it inhibits HIV, by default this makes milk thistle a potential cure or at least a treatment for HIV.
Does Milk Thistle help hepatitis?
A 2007 Cochrane review of research analyzed studies that have tested milk thistle on patients with hepatitis. The studies tested 1,088 patients with alcoholic-related hepatitis, as well las hepatitis B or C viruses.
The research concluded that over all the studies, milk thistle did indeed reduce the incidence of death among the hepatitis patients ("liver mortality"). However, these included studies considered "low quality" by Cochrane standards.
When the low-quality studies were removed, the studies showed milk thistle did not have "significant" effect on reducing hepatitis deaths. They concluded that more high-quality research was needed.
However, a 2024 review of research found more conclusive evidence, notably that milk thistle improved liver function and helped correct enzyme levels.
The researchers concluded:
"Silymarin, a flavonoid complex derived from the milk thistle plant, has emerged as a promising antioxidant therapy for managing CLDs such as NAFLD, chronic hepatitis, ALD, and cirrhosis. Through its potent antioxidant, anti-inflammatory, and hepatoprotective properties, silymarin has shown efficacy in improving liver function, reducing oxidative stress, and mitigating liver inflammation."
Other herbs proven to be antiviral include goldenseal. Thyme has also been shown to be antiviral. And ginger has been proven to be antiviral as well according to other research.
Scientific References
McClure J, Lovelace ES, Elahi S, Maurice NJ, Wagoner J, Dragavon J, Mittler JE, Kraft Z, Stamatatos L, Horton H, De Rosa SC, Coombs RW, Polyak SJ. Silibinin Inhibits HIV-1 Infection by Reducing Cellular Activation and Proliferation. PLoS One. 2012;7(7):e41832.
McClure J, Margineantu DH, Sweet IR, Polyak SJ. Inhibition of HIV by Legalon-SIL is independent of its effect on cellular metabolism. Virology. 2014 Jan 20;449:96-103. doi: 10.1016/j.virol.2013.11.003.
Dhande D, Dhok A, Anjankar A, Nagpure S. Silymarin as an Antioxidant Therapy in Chronic Liver Diseases: A Comprehensive Review. Cureus. 2024 Aug 17;16(8):e67083. doi: 10.7759/cureus.67083.
Wu J, Wen L, Liu X, Li Q, Sun Z, Liang C, Xie F, Li X. Silybin: A Review of Its Targeted and Novel Agents for Treating Liver Diseases Based on Pathogenesis. Phytother Res. 2024 Sep 23. doi: 10.1002/ptr.8347.
Abenavoli L, Izzo AA, Milić N, Cicala C, Santini A, Capasso R. Milk thistle (Silybum marianum): A concise overview on its chemistry, pharmacological, and nutraceutical uses in liver diseases. Phytother Res. 2018 Nov;32(11):2202-2213. doi: 10.1002/ptr.6171.
Rambaldi A, Jacobs BP, Gluud C. Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases. Cochrane Database Syst Rev. 2007 Oct 17;2007(4):CD003620. doi: 10.1002/14651858.CD003620.pub3.
Abenavoli L, Capasso R, Milic N, Capasso F. Milk thistle in liver diseases: past, present, future. Phytother Res. 2010 Oct;24(10):1423-32. doi: 10.1002/ptr.3207.
Giese LA. Milk thistle and the treatment of hepatitis. Gastroenterol Nurs. 2001 Mar-Apr;24(2):95-7. doi: 10.1097/00001610-200103000-00011.