5 Benefits of Milk Thistle: What Is It and How Can It Help My Health?

When it comes to herbal medicines, a seemingly worthless weed can hold a valued plant compound for health, like a diamond in the rough.

That’s certainly the case with milk thistle.

Also known as silymarin or Silybum marianum, milk thistle has been used in traditional medicine for millennia. Indeed, it was used in classical Greece to help liver and gallbladder problems, as well as to protect the liver against toxins.

In recent years, researchers have studied milk thistle for its anti-inflammatory and antioxidant properties – and how it may help the liver and, surprisingly, many other areas of health, with promising results.

Here’s what is known about milk thistle and how it may benefit you.

What Is Milk Thistle?

Milk thistle is a tall thistle with distinctive white marbling on its shiny, dark green leaves. It gets its name from the milky white sap found in its leaves. The flower head blooms bright magenta or purple, surrounded by sharp, spiny bracts. It’s native to the Mediterranean but was introduced to North America during Colonial times.

According to a Medieval legend, when the Virgin Mary was nursing baby Jesus, some of her breastmilk fell upon milk thistle’s leaves, leaving a spattering of white spots. Thus, milk thistle is also sometimes called St. Mary’s thistle.

In the wild, milk thistle is considered an invasive plant. But it’s also cultivated for medicinal purposes as a natural remedy. Milk thistle is typically extracted from its fruit and seeds, where its active ingredient, silymarin (a group of several related plant flavonoids), is highly concentrated.

Silymarin has proven antioxidant, antiviral, and anti-inflammatory properties, which is the “juice” behind milk thistle’s health benefits. Traditionally, it has been used most often in supporting and/or protecting the health of the liver, kidneys, and gallbladder. Some of its liver benefits have been validated by medical research. Emerging research shows that milk thistle may support health in other important ways as well.

Let’s take a look at what the research indicates.

Milk Thistle and Liver Health

While heart health and healthy blood sugar levels are frequently addressed in public health, liver health is often overlooked. Yet, more than 100 million people in the U.S. have some form of liver health issue.

That’s what makes milk thistle so important. It’s commonly used in complementary medicine for liver support. And although it has a long history of traditional use, scientific study of milk thistle’s silymarin is relatively recent.

In the late 1980s, it was studied for its protective effects – thought to come from its antioxidant and tissue regenerative properties – in alcohol-related liver damage.

When the liver metabolizes alcohol (or other toxins), free radicals are produced, and they can cause cellular damage. Researchers believed (and still do) that silymarin helps reduce oxidative stress, which in turn helps to protect intact liver cells or cells not yet irreversibly damaged.

Significantly, a 1989 placebo-controlled clinical study involving 170 participants showed that the silymarin-taking group of individuals with serious liver health problems had increased survival rates over the study’s control group.

Although a small study, it got the scientific community’s attention. A similar type of liver health problem, prevalent amongst obese individuals with blood sugar issues, showed improvement with silymarin supplementation in a 2013 study involving 72 participants.

More studies have since been conducted on silymarin and liver function – but with mixed results and no conclusive benefits. Some experts say that these studies have been poorly constructed, are small, and more quality research is needed.

Still, on the whole, medical researchers view milk thistle’s potential for addressing a number of liver health issues very optimistically.

Impressed with preclinical data (gathered from animal and in vitro research), in a 2024 narrative review, researchers lauded silymarin’s potential to help address serious liver health issues caused by too much alcohol consumption, obesity and blood sugar problems, viral-related inflammation, and more. Many clinical trials are currently underway.

5 Additional Potential Benefits of Milk Thistle

Milk thistle’s health benefits don’t stop with the liver. Emerging and preclinical research shows it may help support health in the following ways:

May Help to Improve Blood Sugar Regulation

In a recent review study, individuals with blood sugar issues who routinely took silymarin showed a significant improvement in their fasting blood sugar levels. The study noted that more research should be conducted to further understand and validate silymarin’s effects.

May Help Protect Against Age-Related Cognitive Decline

In vitro research shows that silymarin may protect against oxidative damage to brain cells. Additionally, it helped reduce amyloid plaques in the brains of test animals with neurodegenerative brain health issues. Amyloid plaques can build up in between nerve cells as one grows older and are associated with cognitive decline. Of course, human studies are needed to further validate these findings.

May Help Menopausal and Postmenopausal Women

A human study involving 80 menopausal women with hot flash symptoms showed that silymarin supplementation can help decrease the frequency and severity of hot flashes significantly.

Preclinical research shows that milk thistle supplementation may stimulate bone mineralization and potentially protect against bone loss, making it a useful therapy for postmenopausal women who are at higher risk of bone loss issues.

May Boost Breast Milk Production in Lactating Mothers

Milk thistle may boost levels of the milk-producing hormone prolactin. In a randomized controlled study involving more than 400 lactating mothers, the mothers taking silymarin for roughly two months produced 64% more milk than those taking a placebo. As the only existing study, more research is needed before supplementation can be recommended for lactating women.

May Help with Seasonal Allergies

A randomized clinical trial showed that individuals with allergies affecting the nasal passages who took silymarin along with other allergy medication improved significantly. As oxidative stress plays a role in the development of allergies affecting the nasal passages, silymarin’s antioxidant power is believed to be behind the results.

Supplementing With Milk Thistle

If you’re interested in taking milk thistle, talk to your medical doctor first. Milk thistle has been shown to be very safe, but it may interact with certain medications. In some cases, it may cause mild gastrointestinal discomfort. In rare instances, it may cause serious allergic reactions.

Milk thistle is available as capsules, tablets, liquid extracts, and tea.

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