What Is Milk Thistle?

Herbal Remedy Commonly Used for Liver Health

Milk thistle capsules, tablets, tea bags, and tincture

Verywell / Anastasia Tretiak

Milk thistle (Silybum marianum) is a perennial herb believed to have medicinal properties. The seeds contain silymarin, a group of compounds said to have antioxidant and anti-inflammatory effects. Milk thistle is commonly used as a home remedy to treat liver problems, often under the presumption that it will "detoxify" the liver.

At present, there is not enough scientific data to say whether milk thistle can help the liver or not. While it is not without benefit, milk thistle doesn't appear to exert a significant effect on either liver tissues or liver function.

Milk thistle is also known by the names Saint Mary's thistle, variegated thistle, and Scotch thistle. In traditional Chinese medicine, milk thistle is referred to as da ji, while the seeds are called shui fei ji.

What Is Milk Thistle Used For?

Although milk thistle is most often used for liver conditions, such as hepatitis and cirrhosis, the herb is believed some to prevent or treat high cholesterol, diabetes, heartburn, upset stomach (dyspepsia), hangover, gallbladder problems, menstrual pain, depression, and even certain types of cancer. Few of these claims are supported by hard evidence.

Here is what some of the current research says:

Liver Disease

Some preliminary studies have suggested that silymarin may improve liver function by keeping toxic substances from binding to liver cells. However, studies on the milk thistle's effectiveness in treating liver disorders have yielded mixed results.

According to a comprehensive review of studies in the American Journal of Gastroenterology, milk thistle neither improves liver function nor reduces the risk of death in people with alcoholic liver disease, hepatitis B, or hepatitis C.

Several smaller studies have suggested that milk thistle may benefit people with mild, subacute (symptom-free) liver disease. An early study from Finland found that a four-week course of silymarin supplements lowered key liver enzymes in people with subacute disease, suggesting the liver was functioning more normally.

Despite the positive findings, subsequent studies have been unable to replicate the results or demonstrate that milk thistle prescribed on its own would render the same effects.

Chronic Hepatitis C

Milk thistle is sometimes used by people with chronic hepatitis C (a viral infection characterized by the progressive scarring of the liver). In fact, a survey funded by the National Institutes of Health reported that 23 percent of 1,145 people with hepatitis C used herbal supplements, with milk thistle being by far the most common.

According to the survey, people with hepatitis C reported fewer symptoms and a "somewhat better quality of life" when taking milk thistle despite having no measurable change in viral activity or liver inflammation.

A 2012 study published in the Journal of the American Medical Association (JAMA) confirmed this. Despite being well-tolerated in the study participants, silymarin (prescribed thrice-daily in 420- or 700-milligram doses) had no tangible effect on liver enzymes.

Given these contradictions, many scientists believe that milk thistle delivers something of a placebo effect in which a person feels an improvement in symptoms despite having no change in their clinical condition.

Type 2 Diabetes

Several studies have suggested that milk thistle may be beneficial for people with diabetes, most notably in those with type 2 diabetes.

According to 2015 research published in Phytomedicine, a 45-day course of silymarin increased the antioxidant capacity and reduced generalized inflammation in adults with type 2 diabetes better than a placebo.

According to the study's authors, the findings suggest that silymarin may reduce the oxidative stress typically associated with diabetes complications.

A systematic review conducted in 2016 further concluded that the routine use of silymarin appears to reduce the fasting blood glucose and HbA1C levels, although the authors warned that the quality of the reviewed studies was poor.

Possible Side Effects

Milk thistle may trigger a number of side effects, including headache, nausea, diarrhea, abdominal bloating, and gas. Less commonly, muscle aches, joint pain, and sexual dysfunction have been reported.

Allergic reactions are also possible. People with allergies to ragweed, daisies, artichokes, kiwi, or plants in the aster family may also be allergic to milk thistle. On rare occasion, milk thistle can cause a potentially life-threatening, all-body allergy known as anaphylaxis.

Call 911 or seek emergency care if you experience shortness of breath, rash, hives, rapid heartbeat, lightheadedness, or swelling of the face, tongue, or neck after taking milk thistle.

If left untreated, anaphylaxis can lead to shock, coma, cardiac or respiratory failure, or death.

Drug Interactions

Milk thistle may reduce your blood sugar, so it needs to be used with caution as it may trigger hypoglycemia (low blood sugar) in people on diabetes medications.

Milk thistle can change the way that your body metabolizes certain drugs in the liver, triggering interactions with:

  • Antibiotics like Biaxin (clarithromycin)
  • Anticoagulants like Coumadin (warfarin)
  • Nonsteroidal anti-inflammatory drugs (NSAIDs) like Advil (ibuprofen), Celebrex (celecoxib), and Voltaren (diclofenac)
  • Statin drugs like Mevacor (lovastatin) and Lescol (fluvastatin)

Other interactions are possible. To avoid complications, always advise your healthcare provider about any supplements or herbal remedies you are taking.

Milk thistle capsules
Verywell / Anastasia Tretiak

Dosage and Preparation

There are no guidelines directing the appropriate use of milk thistle. Milk thistle supplements are commonly sold as in capsule form but are also available as tablets, tea bags, and oral tinctures. Doses range from 175 milligrams to 1,000 milligrams. Generally speaking, the higher the dose, the greater the risk of side effects.

Combination remedies such as Iberogast drops (used to treat dyspepsia) and Barberol tablets (formulated for diabetics) are considered effective with milk thistle doses of 10 milligrams and 210 milligrams, respectively. Higher doses don't necessarily correspond to better results.

Dietary supplements containing milk thistle are sold in natural foods stores, drugstores, and stores specializing in herbal products. You can also purchase milk thistle products online.

What to Look For

Dietary supplements in the United States do not need to undergo the rigorous testing and research and testing that pharmaceutical drugs do. Because of this, the quality can vary from one supplement to the next.

To ensure quality and safety, choose products that have undergone testing and certification by an independent certifying body like the U.S. Pharmacopeia (USP), ConsumerLab, and NSF International. As an added layer of safety, opt for brands that have been certified organic under the regulations of the U.S. Department of Agriculture (USDA).

Be wary of dried whole milk thistle or milk thistle seeds, both of which are vulnerable to fungal contamination, according to research published in the International Journal of Food Microbiology.

By contrast, fungal contamination is rare in milk thistle tea bags, extracts, capsules, tablets, and soft gels.

Frequently Asked Questions

  • Can you grow your own milk thistle?

    Yes, you can grow your own milk thistle. Milk thistle is a hardy plant that grows well in most environments, although it prefers high temperatures and dry conditions. The soil also needs to be well drained.

  • What is silymarin?

    Silymarin is a compound from milk thistle seeds that is said to offer antioxidant and anti-inflammatory benefits. One study on silymarin found that it interfered with the accumulation of liver fat, which means it could aid in the treatment of non-alcoholic fatty liver disease.

  • Does milk thistle cause any side effects?

    Possible side effects of milk thistle can include headache, nausea, diarrhea, abdominal bloating, and gas. Some reports have mentioned muscle aches, joint pain, and sexual dysfunction as well.

    Milk thistle can also cause an allergic reaction in some people. If you have an allergy to ragweed, daisies, artichokes, kiwi, or plants in the aster family, it might be smart to avoid milk thistle.

  • Is milk thistle available as a tea?

    Yes, milk thistle supplements can come in the form of tea bags to brew your own tea. The supplement is also sold as a tablet, capsule, and oral tincture.

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8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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