Milk thistle (Silybum marianum) is a member of the asteraceae family and has a large purple flower.1 It comes from the Mediterranean region, but after having been introduced to other parts of the world, it’s become naturalized in South America, North America and Southern Australia.

The plants can grow up to 5 feet tall and are covered in spines. They have a long history of being used as an edible, medicinal plant. The earliest record of milk thistle was made by Dioscorides, who thought it helped snake bite.2 Pliny the Elder wrote about its use in supporting liver health.

In the following decades, others also wrote about using milk thistle, including herbalist Nicholas Culpepper and late-19th century physicians Harvey Wickes Felter and John Uri Lloyd. Native Americans used the plant to treat skin conditions and boils. Homeopathic practitioners have used the seeds to treat liver conditions such as jaundice, as well as varicose veins and gallstones.

In Germany, herbal medications are used and researched under the guidance of the German Federal Institute for Drugs and Medical Devices Commission E, which is often referred to as the German Commission E.3 The group “recommends it [silymarin] for treatment of toxin-induced liver problems and liver cirrhosis, and as a supportive treatment for chronic diseases of the liver.”4

Basics of Milk Thistle Benefits

The largest bioactive components in milk thistle are flavonolignans.5 These compounds can modulate cell-signaling pathways and reduce inflammation. The active component in milk thistle is silymarin, which is a group of flavonolignans that work together and can be isolated from the seeds.6

Silymarin has several components, including antioxidants and several other biological properties, which are derived from the seeds.7 They include silybins A and B, isosilybin A and B, silychristin (silichristin) and silydiamin. When combined, silybins A and B are called silibinin.8

The terms milk thistle and silymarin have been used interchangeably, although this is technically inaccurate. Lab studies have shown that silymarin can stimulate detoxification and regeneration of liver tissue. In fact, silymarin’s effect on the liver is so great that some researchers have called it “the most potential drug to treat almost all kind of liver diseases.”9

Silyman’s Role in Cancer

Milk thistle stabilizes cellular membranes and inhibits the growth of certain cancers. In some instances, it has been found to potentially increase the effectiveness of specific chemotherapeutic drugs while protecting the liver.10 Since those drugs can also be toxic to the liver, finding a way to protect liver function while under chemotherapy can help improve a patient’s health.11

Scientists also have found that silymarin can help protect the liver from oxidative stress driven by reactive oxygen species and cytokines. In one study12 with children being treated for acute lymphoblastic leukemia, researchers divided the participants into two groups. One received silymarin in three divided doses for one week after each dose of methotrexate, and the second received a placebo.

Before the research began, there was no significant difference in the children’s liver and renal function. After chemotherapy, the group receiving silymarin showed improved liver and kidney function.

Silibinin is one component of silymarin. It has demonstrated significant effects against a variety of malignancies. In one study,13 it showed the ability to down-regulate two pathways to suppress the growth of cancer cells.

In another lab study,14 cells from estrogen-dependent breast carcinoma were cultured and treated with silymarin, doxorubicin or a combination of doxorubicin and silymarin. Researchers found that silymarin had a synergistic effect on doxorubicin, a chemotherapeutic agent used in breast cancer.15

But, that doesn’t mean silymarin should be taken automatically as an adjunct to all cancer treatment, as it can negatively interact with some chemotherapy agents. For example, since silymarin has estrogenic effects, it can counteract hormone inhibitors given for hormone-receptive breast cancer.16 So, always check with your physician first, if you want to use silymarin in conjunction with your cancer treatment.

Currently, milk thistle can be purchased as a dietary supplement. However, Siteman Cancer Center warns that taking the supplement may introduce a few adverse side effects. For example, some side effects can include anorexia, gastrointestinal disturbances and nausea.17 And, as mentioned, use caution with Western medicine chemotherapeutic agents.

Milk Thistle Supports Liver Health and Repair

In lab studies and animal models, silymarin has demonstrated the ability to prevent or reduce liver injury after exposure to certain toxins, including acetaminophen and Amanita phalloides, a type of poisonous fungus.18 However, in human studies on milk thistle’s benefit to your liver, some data have been inconclusive.

For example, some studies found no benefits to support milk thistle’s use for chronic hepatitis C or nonalcoholic fatty liver disease (NAFLD). On the other hand, in at least one animal study,19 researchers combined taurine and silymarin and found that, together, they could effectively reduce both lipid accumulation in the liver and insulin resistance.

And, antiviral activity has been documented with the intravenous use of silibinin against hepatitis C. In one case report of an individual who was infected with both hepatitis C and HIV, two weeks of silibinin administered intraveneously cleared both hepatitis C and HIV.20

The Caspian Journal of Internal Medicine21 also writes that silymarin has an effect against nonalcoholic steatohepatitis (NASH), a more advanced form of NAFLD. It can also help alleviate cirrhosis of the liver and boost liver function.22

Data published in the European Review for Medical and Pharmacological Sciences support the finding that treatment with silymarin plus vitamin E could help patients with NAFLD. The study team concluded:23

“Silymarin can be an alternative valid therapeutic option particularly when other drugs are not indicated or have failed or as a complementary treatment associated with other therapeutic programs.”

Silymarin Is Hepatoprotective Against Certain Poisons

Silymarin has demonstrated the ability to protect the liver against acute alcohol poisoning (alcohol-induced hepatotoxicity) in a study involving animals.24 As already mentioned, it may also offer some hope to those who accidentally eat the amanita mushroom, also known as the death cap.25

To give you an idea of just how deadly the death cap mushroom is, just one can kill a healthy adult and its compounds are extremely stable.26 This means soaking, cooking or drying does not remove the poison from the mushroom. Symptoms start six to 16 hours after eating, depending upon how much was consumed and the health of the person who ate it.

Symptoms begin with stomach pain, vomiting and diarrhea that continues for one to two days. In the following two to three days the person appears as if they’ve recovered. After this is the terminal phase, in which the stomach pain, vomiting and diarrhea are accompanied by evidence of liver damage, which then leads to death.

But, even so, a review in Lancet Oncology suggests that silymarin given intravenously may very well save your life if you ingest this mushroom:27

“A review of more than 2000 patients exposed to amanita mushrooms in Europe and North America suggested that intravenous silybinin was the most effective therapy available against this toxin.”

More Health Benefits of Milk Thistle

Milk thistle can also increase milk production in lactating mothers.28 In the past, silymarin has been used to improve milk production in dairy cows. With humans, one research group undertook a study to evaluate the effect it may have on postpartum women.29 Fifty healthy women were enrolled and given silymarin for 63 days. At the end of the study the researchers found that milk production had increased by 85.94%.

This was much higher than the group receiving the placebo, who increased milk production by 32.09%. None of the participants dropped out during the study and no women reported unwanted side effects.

Milk thistle is also a bacteria-fighter: Data have shown that it may inhibit bacterial growth and biofilm formation.30 In one study published in the Journal of Clinical Immunology,31 researchers evaluated the effects of silymarin and found it could reduce biofilm viability and that it had antibacterial activity against standard bacterial strains.

Researchers believe milk thistle’s anti-inflammatory effects may be in part due to a two-phase process, similar to that used by curcumin and epigallocatechin gallate (EGCG), which is an antioxidant found in green tea.32 In the first phase there is an increase in the expression of genes associated with cellular stress. The second phase involves a longer suppression of gene expression and inhibition of inflammatory signaling pathways.

Silymarin can also activate AMP activated protein kinase (AMPK), which is an enzyme sometimes called the “metabolic master switch.”33 This is because AMPK plays an important role in regulating metabolism.

Silymarin can also inhibit mammalian target of rapamycin (mTor), which is beneficial since activation increases your risk of cancer. Historically, milk thistle had been used to treat those who had mental health conditions. Recently, it has been found silymarin has neuroprotective effects and may help address memory loss triggered by oxidative stress.34

Effects on Neurological System and Blood Sugar

Animal models have been used to test the effects of silymarin on Alzheimer’s disease,35 Parkinson’s disease36 and cerebral ischemia.37 In each study the researchers found that the test animals benefited from using supplementation to reduce the effects of the condition.

Unfortunately, there are few, if any, studies on whether silymarin might also be useful for other neurological diseases such as Hungtington’s disease, amyotrophic lateral sclerosis (ALS) and multiple sclerosis.38

The compound has known effects on blood sugar.39 Taking it daily can lower hemoglobin A1c levels, which means that for people with Type 2 diabetes and taking insulin, extra care has to be taken because it can cause your blood sugar to drop too low.

Take Care if You Plant Milk Thistle at Home

Before you consider planting milk thistle in your backyard, be forewarned: It’s a highly invasive, quickly-spreading weed. You may not mind having it all over your yard, but it is no respecter of boundaries. This means it’ll likely end up in your neighbor’s yard as well.

Milk thistle is also toxic to livestock, so don’t plant it outside if you have grazing animals nearby. It has adapted to growing just about anywhere, even in poor-quality soil. Ideally, the seeds should be planted in an area that gets full sun. Once the flowers have started to dry, they’ll be ready for harvest.40

Cut the flowers from the plant and place them in a paper bag. Store the bag in a dry place to allow the flower heads to dry. Once you’re certain all the moisture is gone, shake the bag to separate the seeds from the flower head.41 The seeds are best kept in a dry, airtight container. Only remove them when you’re ready to use them.

There are several ways to incorporate milk thistle seeds into your food. They can be powdered in a coffee grinder and sprinkled on salads, added to smoothies or raw juice. You can also use the seeds to make your own tea. You’ll find a recipe for milk thistle tea in my past article “Magnificent Milk Thistle.”

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