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Milk thistle (Silybum marianum) is a well known healing plant that is originally native to southern Europe and Asia, though it is now found throughout the world (in fact, this plant is so common that it’s considered a weed in some places). It is also known as carrdus marianus, blessed milk thistle, St. Mary’s thistle, Mary thistle, variegated thistle, Scotch thistle, Mediterranean thistle, and Marian thistle.
Throughout this article I refer to “silymarin”, which is one of the most significant therapeutic compounds found in milk thistle. However, it’s important to note that in reality, silymarin is actually a COMBINATION of various healing compounds found in milk thistle seeds. This combination that makes up silymarin includes three primary flavonolignans known as silibinin (sometimes called silybin), silychristin, and silydianin. In addition to these three constituents in silymarin, milk thistle also contains other compounds including betaine, apigenin, and silybonol, as well as some proteins, oils, and fatty acids.
Milk thistle supplements are generally standardized to contain at least 80% silymarin, so I refer to milk thistle and silymarin somewhat interchangeably here. If a particular study or application uses either whole milk thistle or exclusively 100% silymarin (or a different compound found in the plant entirely), I have specified this accordingly.
Uses of Milk Thistle
Milk thistle has a wide variety of applications in health and healing, including (but not limited to) the following:
- Weight loss support
- Liver detoxification
- Antioxidant (free radical scavenger)
- Regeneration of liver cells
- Improves bone density and strength
- Reverse hearing loss/improve hearing due to loud sounds
- Protects the dopaminergic system
- Inhibits nitric oxide production
- Enhances neuroplasticity (which is associated with improved mood, memory, and learning abilities)
- Alcoholic cirrhosis/hepatitis
- Viral hepatitis (especially in the treatment of hepatitis C)
- Death cap mushroom (Amanita phalloides) poisoning (as well as other types of poisoning discussed below)
- Anticancer effects
- Reduces inflammation
- Gallbladder disorders/ailments (including gallstones)
- Kidney disorders/ailments
- Varicose veins
- Uterine hemorrhage
- Galactagogue – stimulates breast milk production
- Amenorrhea (delayed/no menstruation)
- Splenic congestion
- High cholesterol
- Increases bile secretion
- Anti-ulcer effects
- Healing after ischemic injury (following strokes)
- Healing after radiation exposure (whether the radiation exposure is therapeutic or not is irrelevant in this case)
In Europe, milk thistle also served as a vegetable and was an important staple food. The leaves of Silybum marianum were de-spined and then eaten or prepared as salads or as you’d prepare spinach. The stalks, roots, and flowers of the milk thistle plant were also eaten as foods. The seeds of milk thistle have a long history as a medicine, dating back to the 4th century B.C. when they were first mentioned. The uses of milk thistle have been listed above, but I want to note that one of the primary and most common uses of milk thistle seeds in ancient Europe (and beyond) was as a galactagogue: an herb that stimulates breast milk production in lactating women.
Below is a more in-depth discussion of some of the specific uses of milk thistle:
Poisoning Treatment for Amanita phalloides Poisoning and Other Toxins
One particularly notable use of milk thistle that has been relatively well studied is in the plant’s ability to reverse poisoning by the Amanita phalloides mushroom, otherwise known as the death cap mushroom. Ingestion of this mushroom causes severe vomiting and diarrhea within 5-12 hours after ingestion and can cause both hypovolemia (decreased blood circulating in the body) and hypoglycemia (decreased glucose in the bloodstream) as a result.
In the studies that looked at silymarin’s effect on mushroom poisoning, it was observed that this compound interrupts the ability of the toxins to bind to liver cells and also prevents recirculation of the poisons through the bloodstream. Treatment in these studies used other compounds in addition to the silymarin, and some studies also used intravenous silymarin treatment (as opposed to only oral supplementation). Readers should note that IV silymarin is not currently available in the United States, but may be available in Germany, India, Mexico, and some other countries.
In the treatment of mushroom poisoning, milk thistle’s main compound, silymarin, blocks the receptor sites for the toxins. This blockage means that the phalloidine and a-amanatine (the toxic compounds in the death cap mushroom) cannot affect the liver cells or other cells in the body. In addition, milk thistle increases the regenerative abilities of the liver cells, so any damage that does occur is more likely to repair itself quickly.
Milk thistle also has notable effects as an antidote for some other toxins/poisons, including:
- Tetracycline (brand names Sumycin, Panmycin, Achromycin V)
- Thallium (heavy metal)
- Erythromycin estolate (brand names Schein, Teva, Geneva, Alpharma, Lederle-U.S.)
- Amitriptyline (antidepressant; brand names Elavil, Endep, Vanatrip)
- Nortriptyline (antidepressant; brand names Pamelor and Aventyl)
- Tert-Butyl hydroperoxide
- Long-term treatment with phenothiazine (antipsychotic; brand names Compazine, Compro, Mellaril, Permitil, Phenadoz, Prolixin, Serentil, Sparine, Thorazine, Torecan, Trilafon, Phenergan)
- Long-term treatment with butyrophenone (antipsychotic; brand names Haldol, Anquil, Droperidol)
- Halothane (brand name Fluothane)
- Acetaminophen (brand name Tylenol)
- Carbon tetrachloride
- Iron overload
- Fungal food poisoning
Milk thistle/silymarin should not be used exclusively as an antidote in the case of poisoning or toxic overload of any of the substances listed above, however it may be a valuable remedy to prevent severe or long-term liver or tissue damage in the case that any of these should be ingested in particularly high quantities (or at a quantity where they’re considered poisonous).
Milk Thistle and Silymarin in the Treatment of Hepatitis and Liver Cirrhosis
There are many different kinds of hepatitis, including viral variants as well as variants brought on by poor lifestyle habits such as alcoholism or drug addiction. Milk thistle and silymarin can help reverse the effects of hepatitis in all of its forms. It is also a valuable therapy for the treatment of liver disease and cirrhosis. Though the US and many other western countries don’t acknowledge the hepatoprotective (liver protective) effects of milk thistle in conventional medicine practices, in Germany the German Commission E permits and supports the therapeutic use of silymarin as a treatment for hepatitis A, chemically-induced hepatitis, and alcoholic cirrhosis, among other related liver diseases.
One study examining the effects of milk thistle/silymarin supplementation followed a group of 106 patients with liver disease, half of which were given a placebo, and the other half were given silymarin. This study demonstrated that the group receiving silymarin supplementation had significantly lower transaminase levels than the placebo group; high transaminase levels are associated with various liver disease and problems since these liver enzymes are released in response to increased toxins or damage in the liver. Lower levels of transaminase following silymarin supplementation suggests that the body didn’t find it necessary to produce these liver enzymes, meaning that the toxic load and/or damage in the liver was likely decreased following supplementation.
A different study examining patients with chronic alcoholic liver disease noted decreased/normalized levels of bilirubin and the two different kinds of transaminase liver enzymes. As mentioned in the paragraph above, this suggests that healing occurred in the liver to an extent that the body didn’t believe it was necessary to produce bilirubin or transaminase in such high quantities anymore. Yet another study followed the progress of 20 patients with chronic active hepatitis, approximately half of whom were placed on a silymarin and phosphatidylcholine supplementation protocol. The group taking the milk thistle supplement showed notably lower levels of bilirubin, transaminase enzymes, and gamma-glutamyl transpeptidase enzymes. The study observed that a combined silybin-phosphatidylcholine supplement appeared to have a more significant effect than silymarin, milk thistle, or silybin alone, suggesting that this particular combination may increase the bioavailability of milk thistle’s healing constituents.
The fact that all three of these studies mentioned above showed such similar outcomes in liver disorders following supplementation with silymarin is validating in terms of the efficacy of milk thistle and silymarin as a potential liver healer. Nevertheless, some other studies didn’t note any significant changes following supplementation with silymarin.
Liver fibrosis is another issue that silymarin may be capable of treating, particularly when it’s combined with other therapies. This can be caused by a variety of different factors, including hepatitis, fatty-liver disease, alcoholic liver disease, and biliary obstruction, among other issues. Fibrosis in the liver can lead to the liver’s decreased ability to remove toxins from the body (sometimes resulting in compromised brain function) or perform other essential functions. According to some studies, milk thistle, particularly when administered with a standardized silymarin content or when silymarin is administered by itself, inhibits specific processes in the liver that may lead to fibrosis.
Anti-Inflammatory Effects of Milk Thistle and Silymarin
Milk thistle is naturally anti-inflammatory. Because inflammation plays such a significant role in the development and continuation of disease, compounds like silymarin in milk thistle that are anti-inflammatory can be extremely important for recovery. Even some health issues like allergies or asthma that are not considered “diseases” often find their roots in inflammation.
Milk thistle seed works by blocking the formation of certain inflammatory agents in the body, such as prostaglandins and leukotrienes. It also prevents the release of histamine, the primary agent responsible for all kinds of allergic reactions (as well as a major player with inflammation in general). This specific mechanism makes it a potentially valuable therapy for people with chronic allergies, asthma or asthmatic symptoms, and arthritis.
One study on silymarin in the treatment of arthritis noted, however, that the compound may be more effective in relieving arthritis that is only just developing rather than treating arthritis that has already developed. Thus, though milk thistle is likely to benefit anyone with arthritis due to its anti-inflammatory nature, it’s not as likely that it would cure or totally relieve symptoms for people who have already developed a fully blown version of arthritis.
Immunomodulation and Anti-Viral Activity of Milk Thistle
Milk thistle helps regulate immune system function and can also be used as an antiviral herb in some cases. As an anti-inflammatory, as discussed above, the plant reduces the production of histamines and certain other inflammatory agents that may be blamed for cytokine storm syndrome. In this way, it can help modulate the immune system by preventing or reducing an overreaction. In addition, however, milk thistle can also increase and improve the function of the immune system for people whose immune systems may not be functioning optimally. When milk thistle is given over a longer period of time, it can increase the production of T-lymphocyte and interleukin immune cells, thus improving the immune response. For people with an auto-immune disease, milk thistle can lower immunoglobulin levels and reduce the symptoms of the disease in some cases.
Milk thistle also reduces the production of Tumor Necrosis Factor Alpha (TNF-a), a primary cytokine implicated in cytokine storm syndrome. For patients who are struggling to recover from an acute viral or bacterial infection, high levels of TNF-a can cause severe tissue and organ damage and thus finding ways to reduce the production of this cytokine is extremely important in these situations.
As an antiviral, milk thistle has specifically been used in the treatment of viral hepatitis. Studies have shown that silymarin can inhibit the growth of particular viral hepatitis cells, including Heb3B (a type of hepatitis B virus cell) and HepG2 (a different hepatitis B cell type). The effects of silymarin against the Hep3B cells were more significant with the possibility of even inducing cell death when administered as a treatment for viral hepatitis B of this type. In the treatment of hepatitis B, silibinin was the primary constituent used as a medicine.
Milk Thistle as a Treatment for Cancer
Silymarin has notable anti-cancer effects, specifically in the treatment of the following cancers/tumor types:
- Prostate cancer/tumor
- Tongue squamous cell carcinoma
- Breast cancer
- Cervical cancer
- Skin cancer
- Small cell lung cancer
- Non-small cell lung cancer
- Colon cancer
- Bladder cancer
- Hepatocellular cancer
Milk thistle may be administered as a cancer treatment either by oral, intravenous, or topical application. As an oral therapy, it’s best to use a standardized, capsulized form of the herb rather than a tea because the silymarin in milk thistle is more bioavailable in the capsulized form, and thus is more powerful. Intravenous therapy with silymarin isn’t available everywhere so it may not be an option for all patients, however individuals located in/with access to Germany, India, or Mexico or some other countries may be able to take advantage of IV therapy with silymarin. The topical application of milk thistle should specifically be used in cases where it’s being used in the treatment of skin cancer.
Milk thistle can prevent tumor growth as well as promote cancer cell death in tumors that have already developed. In addition, it can be a helpful adjunct therapy for patients who have chosen to receive chemotherapy or radiation because it protects the liver and other organs from toxicity and tissue damage that may occur as a result of these treatments during the course of the illness.
Milk Thistle as an Antidepressant and Neuroprotective Agent
Traditionally, milk thistle was used commonly as an antidepressant. Even before modern science was able to crack open the “why” of milk thistle’s effects on the body, people in Europe were using this plant to improve and regulate mood. Today, we know that milk thistle protects and supports the dopaminergic neurons in the brain from certain types of neurotoxicity. Because of this support that milk thistle offers this system in the brain, the dopaminergic system is able to produce and release dopamine more effectively, resulting in a better and more balanced mood.
For the treatment of depression, anxiety, or other dopamine-related problems (such as many types of addiction), milk thistle may combine well with Mucuna pruriens, a plant that contains higher quantities of L-dopa, the precursor to dopamine in the brain. The combination of these two plants would allow the brain to repair any potential damage to the dopaminergic system using the compounds found in silymarin (and then also ward off any future damage) while also getting plenty of the raw materials it needs to actually make the dopamine.
Milk Thistle as a Diabetes Treatment
One study demonstrated that silymarin was able to decrease blood glucose levels in diabetic test subjects in addition to reducing insulin requirements. Plus, milk thistle has anti-ulcer effects. Because some diabetics struggle with ulcers, milk thistle may be a valuable therapy on a few different levels for people with this disease.
Dosage and Administration of Milk Thistle
Milk thistle contains a flavonoid called silymarin that is responsible for a lot of the plant’s therapeutic actions. Below we have dosage and administration methods for both milk thistle as well as for silymarin (sometimes dried milk thistle may be marketed as “silymarin”, especially if the silymarin content has been standardized, so we’ve chosen to include information about these various forms here).
Milk thistle may be sold in a dried herb mix in capsule form or as a liquid extract or tincture. A silymarin-phosphatidylcholine complex (in capsule form) may also be available.
Milk thistle is often given at a dosage of 150-175mg of the plant extract, standardized to contain 80% silymarin. This dose should be administered 3 times daily. If you are using silymarin (not the whole plant extract), then the dosage is 420-480mg of silymarin administered 2-3 times daily. One specific brand known as Ultrathistle, which is the whole plant extract bound with phosphatidylcholine, should be administered in doses of one 360mg capsule, 3 times daily.
Side Effects and Contraindications
Though most people will not experience notable side effects from taking milk thistle (side effects are quite rare), there are still some side effects that you may experience (especially if you’re taking higher doses). Some people taking milk thistle internally will have diarrhea, stomach upsets, and/or nausea and vomiting. Touching a milk thistle plant may result in rash.
Milk thistle should be used with caution if you are currently taking antipsychotics, Phenytoin (Dilantin), Halothane, birth control medication, or hormone replacement therapy medications. Because many of these medications are absorbed in the liver, their absorption or functionality in the body may be impaired because of milk thistle’s effects on liver health.
Other medications that are absorbed by the liver (and therefore may not be well absorbed if you’re taking milk thistle at the same time) include:
- Allergy drugs (like Allegra, fexofenadine)
- High cholesterol medications (such as statins, like Mevocor or Altacor)
- Anti-anxiety drugs (Xanax, alprazolam; Valium, diazepam; Ativan, lorazepam etc.)
- Antiplatelet and anticoagulants (blood thinners), including Plavix (clopidogrel) and Coumadin (warfarin)
- Some cancer medications (including Raloxifene)
Although milk thistle can interfere with the absorption of these medications, it’s not likely to produce a reaction when combined with any medications. Overall, it’s a very safe supplement to take, even if you’re currently on any of these drugs. Nevertheless, always consult with your doctor before starting any supplementation protocol and if there’s a chance that interference of the absorption of these medications will pose a risk to your life, then proceed with caution.
If you are allergic to ragweed, chrysanthemums, marigolds, chamomile, yarrow, or daisies, do not take milk thistle. These plants are all a part of the same family of plants (the Asteraceae family) and are closely related to each other. Therefore, if you have an allergy to any plant in this family of plants, you should not take milk thistle because the possibility is fairly high that it will also cause an allergic reaction.
Women who are pregnant should use milk thistle with caution, as it has not been studied in depth during pregnancy yet. It should also not be used in young children for the same reason. Although there aren’t a large number of modern safety studies on the use of milk thistle during breastfeeding, because the plant has been used for thousands of years as a galactagogue, it’s probable that it’s safe during breastfeeding in most cases (as long as it’s not used in particularly large quantities and you don’t fit the profile for any of the other contraindications listed above). Nevertheless, use caution with any herb while pregnant, breastfeeding, or administering medicines to small children or infants.
Nootropics Depot (2019). The Top 5 Milk Thistle Health Benefits. Retrieved November 30, 2021 from: https://nootropicsdepot.com/articles/the-top-5-milk-thistle-health-benefits/
Mount Sinai, New York (2021). Milk Thistle Information. Retrieved November 30, 2021 from; https://www.mountsinai.org/health-library/herb/milk-thistle
Rainone, Francine (2005). Milk Thistle. Retrieved December 20, 2021 from: https://www.aafp.org/afp/2005/1001/p1285.html#afp20051001p1285-b36
Bhattacharya, Sanjib (2011). Phytotherapeutic properties of milk thistle seeds: An overview. Retrieved December 20, 2021 from: https://www.researchgate.net/publication/266211306_Phytotherapeutic_properties_of_milk_thistle_seeds_An_overview