milk thistle

What Is It?
Health Benefits
Dosage Information
Guidelines for Use
General Interaction
Possible Side Effects
Evidence Based Rating Scale

What Is It?

Healers have used the prickly milk thistle plant to treat liver ailments for more than 2,000 years. Somehow these early practitioners figured out that preparations of this purple-flowered member of the sunflower family could stimulate the flow of bile from the liver, improving digestion and various liver-related ills.

Interestingly, bile and other bodily fluids, also known as humors, were once associated with different personality types. Because it was thought that black bile was inherent to a melancholic nature, milk thistle was prescribed for treating depression and melancholy (which actually means "black bile"). Today, the word "biliousness" and the phrase "having excess bile" are still used to describe negative personality traits.

While milk thistle is no longer seen as a remedy for melancholy, hundreds of medical studies have substantiated the fact that the herb does indeed protect and heal the liver. European physicians currently consider milk thistle a mainstay for liver disorders ranging from hepatitis to cirrhosis. But even though a 19th-century American medical group called the Eclectics prescribed milk thistle for liver ailments, it has never gained widespread conventional use in the U.S. for healing purposes.

Milk thistle grows throughout the world (including North America) in both cultivated and wild form. Many sources refer to the herb by its botanical name, Silybum marianum, as well as by its active compounds, collectively known as silymarin. Concentrated stores of silymarin are found in the herb's shiny black fruits (seeds), which are typically collected at summer's end.

Health Benefits

Although most commonly used for liver complaints, milk thistle is also being examined as a treatment in various other settings, including prevention of hangover. As a potent antioxidant, the versatile milk thistle extract helps prevent highly reactive oxygen molecules called free radicals from damaging cells throughout the body, but especially in the liver, stomach, and intestines.

An injectable form of milk thistle is a powerful antidote to mushroom poisoning. And the oral extract shows promise for minimizing liver damage resulting from chemotherapy. This derives from the herb's antioxidant actions as well as its ability to accelerate the elimination of toxic compounds that can accumulate in the body.

Specifically, milk thistle may help to:

  • Treat acute and chronic liver disease. Milk thistle nourishes the liver, a vital organ responsible for processing everything from nutrients in foods to medications and chemical pollutants (1,2). The herb partly accomplishes this task by preventing a reduction in concentrations of glutathione, an amino-acid-like compound that is critical to neutralizing toxins. Some studies indicate that milk thistle can increase glutathione levels by as much as 35%.

·         In addition, silymarin alters the outer membranes of liver cells in such a way that bars toxins from entering. It even encourages the formation of new, healthier liver cells to replace old, damaged ones. Various types of liver damage benefit from these remarkable properties, and the herb has repeatedly demonstrated its power to do so (3).

·         An Egyptian study of 177 people suffering from chronic hepatitis C found that individuals supplementing their diets with milk thistle tolerated the preparation well throughout the one-year study. During this time, the group treated with milk thistle reported fewer disease symptoms and better overall general well-being. These benefits did not, however, translate into the superiority of milk thistle treatment over that of placebo (4). Other larger reviews have also failed to establish clear efficacy of milk thistle in treating chronic liver ailments (5-7). We need more research data before we can recommend milk thistle as a first line treatment for liver disease. However, should the research find milk thistle to be beneficial for these conditions its use will be widespread due to its low incidence of side effects and good tolerability.

  • Treat alcohol-related liver problems. Excessive alcohol intake depletes the amount of toxin-neutralizing glutathione in the liver and can cause severe scarring and dysfunction, a condition called cirrhosis. Milk thistle not only boosts glutathione levels, but it also helps to repair the liver by promoting the growth of new cells in this large and vital organ. Many college students take advantage of this effect by downing milk thistle capsules before drinking alcohol.
  • Numerous small studies have shown beneficial changes in liver toxicity when supplementing with milk thistle (8-10). But larger studies and meta-analyses (comparisons of effects in multiple studies simultaneously) have yet to demonstrate an improvement in liver function and/or mortality due to liver disease (6). More high–quality, large-scale studies are needed to assess what benefit milk thistle might have in the treatment of alcohol-induced liver disease (11).

·         Stopping the growth of breast, prostate, and cervical tumors. In vitro (cells in a dish) and in vivo (live animal) studies have shown that milk thistle components can suppress prostate cancer cell growth and prevent new prostate cancer tumor formation (12-14). Similarly, researchers have shown the active components of milk thistle may work in conjunction with conventional cancer drugs to prevent the spread of breast cancer (15). These studies represent only the beginnings of our scientific investigation of its promise for treating various cancers. Scientists are excited about these preliminary findings and are working toward elucidating the possible benefits of milk thistle supplementation in human cancer trials.

Control psoriasis. The herb has anti-inflammatory properties that may be useful for keeping the characteristic psoriasis rash in check and for slowing the proliferation of abnormal skin cells (16). 


    • tincture
    • tablet
    • softgel
    • liquid
    • capsule

Dosage Information

Special tip:

To work as effectively as indicated in dozens of clinical trials, milk thistle needs to be correctly prepared and standardized. Choose a supplement standardized to contain 70% to 80% silymarin, the main active ingredient. This concentration of silymarin is needed to ensure that a therapeutic amount will reach the bloodstream and, ultimately, the liver.

For all forms of liver problems, including alcohol-related ones: Take 400 to 600 mg standardized extract a day divided into three doses.

Be sure to check out our Dosage Recommendations Chart for milk thistle, which lists therapeutic dosages for specific ailments at a glance.

Guidelines for Use

  • Don't expect teas made with milk thistle to improve any medical condition. They contain only trace amounts of silymarin, which dissolves poorly in water. Also avoid products containing milk thistle leaf which have no therapeutic value (the active ingredients are in the seeds).
  • There are products now available in which silymarin is chemically bound to phosphatidylcholine, a key component of lecithin (a natural fat). These preparations may, in fact, be better absorbed and more effective than unbound milk thistle.
  • Herbal blends that go by such names as "liver complex" and "lipotropic factors" combine milk thistle with other herbs and nutrients. Popular added ingredients include dandelion, methionine, inositol, and choline, compounds believed to enhance liver function and increase the flow of fats and bile from the liver and gallbladder.
  • Take milk thistle 30 minutes before meals for optimal effectiveness.

For chronic conditions, you may need to take the herb for eight to twelve weeks before noticing a benefit.

General Interaction

  • If you are taking the drug indinavir to treat HIV or AIDS, consult your doctor before taking milk thistle, because it may decrease the effectiveness of this drug.  

Possible Side Effects

·         Although milk thistle is generally acknowledged as extremely safe, some individuals have reported mild cases of diarrhea after using it.


  • Don't try to self-diagnose or self-treat a liver problem. Such ailments require the attention of a medical professional who can make an accurate diagnosis and closely monitor your care.
  • Avoid alcohol-based tinctures of milk thistle. Some of these contain considerable concentrations of alcohol, which can damage the liver over time.
  • Milk thistle is widely accepted as safe, even for women who are pregnant or breast-feeding.

Evidence Based Rating Scale

The Evidence Based Rating Scale is a tool that helps consumers translate the findings of medical research studies with what our clinical advisors have found to be efficacious in their personal practice. This tool is meant to simplify which supplements demonstrate promise in the treatment of certain conditions. This scale does not take into account any possible interactions with any medication/ condition/ or therapy which you may be currently undertaking. It is therefore advisable to ask your doctor before starting any new treatment regimen.











Alcoholic Liver Disease










Study results have been mixed. Some randomized controlled trials have shown benefit, but larger meta-analyses did not replicate these findings. More study is needed to determine effectiveness.

















Lab studies performed on cancer cells and in animals appear promising. However, studies have not confirmed beneficial results in humans. More research is needed in human trials.




Date Published: 01/14/2007
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