Questions and Answers About Milk Thistle/2010

  • Wednesday, November 10, 2010
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Questions and Answers About Milk Thistle

What is milk thistle?
Milk thistle is a plant whose fruit and seeds have been used for more than 2,000 years as a treatment for disorders of the liver, bile ducts, and gallbladder. Milk thistle is native to Europe but can also be found in the United States and South America.
The medicinal ingredient found in milk thistle is silymarin, an extract of milk thistle seeds. It is an antioxidant that protects against cell damage. Silymarin contains 4 compounds: silybin (the most active), isosilybin, silychristin, and silydianin. Most research has studied silymarin or its major compound silybin, instead of the plant in its whole form.
The botanical name for milk thistle is Silybum marianum. Milk thistle is also called holy thistle, Marian thistle, Mary thistle, St. Mary thistle, Our Lady's thistle, wild artichoke, Mariendistel (German), and Chardon-Marie (French).
What is the history of the discovery and use of milk thistle as a complementary and alternative treatment for cancer?
The ancient Greeks and Romans used milk thistle as a treatment for liver ailments and snake bites. During the Middle Ages, milk thistle was recommended to treat liver toxins. Modern homeopathic practitioners have used compounds from milk thistle seeds to treat a range of disorders including jaundice, gallstones, and peritonitis. The German Commission E, which studies the safety and efficacy of herbs for the German government, recommends milk thistle for liver damage due to toxins, cirrhosis of the liver, and as a supportive therapy for chronic inflammation of the liver.

Despite milk thistle's long history of use for liver complaints, it was not until 1968 that researchers extracted silymarin from milk thistle seeds and suggested that it might be the plant's active ingredient. Silymarin was later discovered to be a mixture of flavonolignans, a family of plant-based substances with antioxidant effects.
What is the theory behind the claim that milk thistle is useful in treating cancer?
To research the claim that milk thistle is useful in treating cancer, its active substance silymarin and its major compound silybin have been the most widely studied ingredients.
Silymarin and silybin may protect the liver against damage from toxic chemicals by blocking toxins from entering the cell or by moving toxins out of the cell before damage begins.
Silymarin and silybin have been studied in the laboratory in cancer cells as well as in animal tumors of the tongue, skin, bladder, colon, and small intestine.

They have been tested for their potential to:
Make chemotherapy less toxic.
Make chemotherapy more effective.
Stop or slow the growth of cancer cells and block tumors from starting or continuing to grow.
Help to repair liver tissue.
How is milk thistle administered?

Milk thistle is usually taken by mouth in capsules or tablets. Since it does not dissolve well in water, it is not commonly taken as an herbal tea. In Europe, the active compound silybin is given by intravenous infusion as the only effective antidote for Amanita phalloides, a rare mushroom toxin that causes deadly liver failure.
Most milk thistle supplements are measured by how much silybin they contain. Special forms of silybin made to be easily absorbed and used by the body are sold under the names Legalon, silipide, and Siliphos.
Have any preclinical (laboratory or animal) studies been conducted using milk thistle?
Research in a laboratory or using animals is done to find out if a drug, procedure, or treatment is likely to be useful in humans. Preclinical studies are done before clinical trials (in humans) are begun.
Silymarin, the active substance found in milk thistle seeds, has been studied in laboratory research. These studies have shown that it acts as an antioxidant by:
Strengthening cell walls to prevent toxins from crossing into the cell.
Stimulating enzymes that make toxins less harmful to the body.
Blocking damaging substances called free radicals from attacking cells.
Silybin, the major compound found in silymarin, has been studied in laboratory experiments using cancer cell lines (cells adapted to grow in the laboratory). These studies show that silybin:
May help cisplatin and doxorubicin (chemotherapy drugs) work better against ovarian and breast cancer cells.
May have direct anticancer effects against prostate, breast, and cervical cancer cells.
May slow down cell growth, as shown in prostate cancer cell lines.
Tests on colorectal cancer cells transplanted into mice found that silybin given twice a day decreased tumor growth.
Have any clinical trials (research studies with people) of milk thistle been conducted?
There is 1 case report describing the use of silymarin in a patient with promyelocytic leukemia who required breaks in chemotherapy due to abnormal liver enzyme levels. During 4 months of treatment with silymarin, the patient had normal liver enzyme levels and was able to undergo chemotherapy without breaks. A second case report describes a patient with hepatocellular carcinoma whose symptoms improved when he took 450 milligrams of silymarin per day, without anticancer therapy.

A randomized clinical trial in children with acute lymphoblastic leukemia found that silymarin decreased the harmful effects of chemotherapy on the liver without working against the cancer treatment. The children taking silymarin needed fewer chemotherapy dose reductions because of side effects than the children who did not take milk thistle.
A number of clinical trials have studied milk thistle or silymarin in the treatment of patients with hepatitis, cirrhosis, or disorders of the bile ducts. These trials have used a wide range of doses with mixed results. In a trial of biologic therapy for patients with chronic hepatitis, patients taking silymarin had fewer symptoms and a better quality of life compared to patients not taking silymarin. The beneficial effects of silymarin shown in some studies suggest it might play a role in preventing hepatitis and/or liver cancer, but no clinical trials have studied the use of silymarin for prevention.

Have any side effects or risks been reported from milk thistle?
Very few bad side effects from the use of milk thistle or silymarin have been reported when taken as recommended. Several large, carefully designed studies in patients with liver disorders have found that taking silymarin may rarely have a laxative effect or cause nausea, heartburn, or stomach upset. At high doses, mild allergic reactions have been seen (more than 1,500 milligrams a day).

Silymarin has been used in pregnant women who have a bile blockage in the liver, with no toxic effects to the patient or fetus. Silymarin have also been given to children intravenously for mushroom poisoning.

It is not known if milk thistle may make anticancer medications or other drugs more effective, less effective, or have no effect when taken with them.
Is milk thistle approved by the U.S. Food and Drug Administration (FDA) for use as a cancer treatment in the United States?
The U.S. Food and Drug Administration has not approved the use of milk thistle as a treatment for cancer or any other medical condition.
Milk thistle is available in the United States as a dietary supplement. Because dietary supplements are regulated as foods, not as drugs, FDA approval is not required unless specific claims about disease prevention or treatment are made.
Given the limited research done with milk thistle in patients with cancer, using it as a cancer treatment cannot be recommended except in carefully designed clinical trials.

Changes to This Summary (06/18/2010)

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
Changes were made to this summary to match those made to the health professional version.

General CAM Information

Complementary and alternative medicine (CAM)—also referred to as integrative medicine—includes a broad range of healing philosophies, approaches, and therapies. A therapy is generally called complementary when it is used in addition to conventional treatments; it is often called alternative when it is used instead of conventional treatment. (Conventional treatments are those that are widely accepted and practiced by the mainstream medical community.) Depending on how they are used, some therapies can be considered either complementary or alternative. Complementary and alternative therapies are used in an effort to prevent illness, reduce stress, prevent or reduce side effects and symptoms, or control or cure disease.
Unlike conventional treatments for cancer, complementary and alternative therapies are often not covered by insurance companies. Patients should check with their insurance provider to find out about coverage for complementary and alternative therapies.
Cancer patients considering complementary and alternative therapies should discuss this decision with their doctor, nurse, or pharmacist as they would any therapeutic approach, because some complementary and alternative therapies may interfere with their standard treatment or may be harmful when used with conventional treatment.

Evaluation of CAM Approaches

It is important that the same rigorous scientific evaluation used to assess conventional approaches be used to evaluate CAM therapies. The National Cancer Institute (NCI) and the National Center for Complementary and Alternative Medicine (NCCAM) are sponsoring a number of clinical trials (research studies) at medical centers to evaluate CAM therapies for cancer.
Conventional approaches to cancer treatment have generally been studied for safety and effectiveness through a rigorous scientific process that includes clinical trials with large numbers of patients. Less is known about the safety and effectiveness of complementary and alternative methods. Few CAM therapies have undergone rigorous evaluation. A small number of CAM therapies originally considered to be purely alternative approaches are finding a place in cancer treatment—not as cures, but as complementary therapies that may help patients feel better and recover faster. One example is acupuncture. According to a panel of experts at a National Institutes of Health (NIH) Consensus Conference in November 1997, acupuncture has been found to be effective in the management of chemotherapy-associated nausea and vomiting and in controlling pain associated with surgery. In contrast, some approaches, such as the use of laetrile, have been studied and found ineffective or potentially harmful.
The NCI Best Case Series Program, which was started in 1991, is one way CAM approaches that are being used in practice are being investigated. The program is overseen by the NCI’s Office of Cancer Complementary and Alternative Medicine (OCCAM). Health care professionals who offer alternative cancer therapies submit their patients’ medical records and related materials to OCCAM. OCCAM conducts a critical review of the materials and develops follow-up research strategies for approaches deemed to warrant NCI-initiated research.

Questions to Ask Your Health Care Provider About CAM

When considering complementary and alternative therapies, patients should ask their health care provider the following questions:
What side effects can be expected?
What are the risks associated with this therapy?
Do the known benefits outweigh the risks?
What benefits can be expected from this therapy?
Will the therapy interfere with conventional treatment?
Is this therapy part of a clinical trial?
If so, who is sponsoring the trial?
Will the therapy be covered by health insurance?

To Learn More About CAM

National Center for Complementary and Alternative Medicine (NCCAM)
The National Center for Complementary and Alternative Medicine (NCCAM) at the National Institutes of Health (NIH) facilitates research and evaluation of complementary and alternative practices, and provides information about a variety of approaches to health professionals and the public.
NCCAM Clearinghouse
Post Office Box 7923 Gaithersburg, MD 20898–7923
Telephone: 1–888–644–6226 (toll free) 301–519–3153 (for International callers)
TTY (for deaf and hard of hearing callers): 1–866–464–3615
Fax: 1–866–464–3616
Web site:

CAM on PubMed
NCCAM and the NIH National Library of Medicine (NLM) jointly developed CAM on PubMed, a free and easy-to-use search tool for finding CAM-related journal citations. As a subset of the NLM's PubMed bibliographic database, CAM on PubMed features more than 230,000 references and abstracts for CAM-related articles from scientific journals. This database also provides links to the Web sites of over 1,800 journals, allowing users to view full-text articles. (A subscription or other fee may be required to access full-text articles.) CAM on PubMed is available through the NCCAM Web site. It can also be accessed through NLM PubMed bibliographic database by selecting the "Limits" tab and choosing "Complementary Medicine" as a subset.

Office of Cancer Complementary and Alternative Medicine
The NCI Office of Cancer Complementary and Alternative Medicine (OCCAM) coordinates the activities of the NCI in the area of complementary and alternative medicine (CAM). OCCAM supports CAM cancer research and provides information about cancer-related CAM to health providers and the general public via the NCI Web site.
National Cancer Institute (NCI) Cancer Information Service
U.S. residents may call the NCI Cancer Information Service toll free at 1-800-4-CANCER (1-800-422-6237) Monday through Friday from 8:00 am to 8:00 pm. A trained Cancer Information Specialist is available to answer your questions.
Food and Drug Administration
The Food and Drug Administration (FDA) regulates drugs and medical devices to ensure that they are safe and effective.
Food and Drug Administration
5600 Fishers Lane
Rockville, MD 20857
Telephone: 1–888–463–6332 (toll free)
Web site:
Federal Trade Commission
The Federal Trade Commission (FTC) enforces consumer protection laws. Publications available from the FTC include:
Who Cares: Sources of Information About Health Care Products and Services
Fraudulent Health Claims: Don’t Be Fooled
Consumer Response Center
Federal Trade Commission
Washington, DC 20580
Telephone: 1-877-FTC-HELP (1-877-382-4357) (toll free)
TTY (for deaf and hearing impaired callers): 202-326-2502
Web site:

Cases in CAM: Milk Thistle for the Liver -- Any Evidence?
Désirée Lie, MD, MSEd
Authors and Disclosures
Posted: 03/02/2010
Case Study
Mr. Y is a 40-year-old divorced car dealer who admits to binge alcohol consumption over the weekend with his buddies, consisting of 5 to 12 bottles of beer each on Friday and Saturday nights. He reports that he is sometimes inebriated and awakes the following morning with a hangover and amnesia for some of the previous night’s events. His father died of alcoholic cirrhosis at age 54 years. He is on no medications other than acetaminophen for occasional headaches. At his annual physical he expresses a desire to control his alcohol intake because of a new relationship he has forged which he believes has long-term potential. His new girlfriend has urged him to seek medical advice to control his alcohol intake. He denies alcohol dependence manifested as withdrawal symptoms when he misses the 'weekend booze.' His girlfriend brought up milk thistle as a treatment and suggested that he ask the doctor if it can reduce his appetite for beer and/or counteract acute effects of liver damage from alcohol consumption. She was also wondering whether milk thistle could improve her own complexion and reduce wrinkles.

On examination, Mr. Y is healthy and normotensive with no physical signs of chronic liver disease. A metabolic panel including liver function tests (LFTs) is normal. His last alcohol binge was 5 days ago.

Milk thistle (also known as Silybum marianum or silymarin) has been used medicinally for over 2000 years,[1] primarily for the treatment of hepatic and biliary disorders.[2-5] A flavonoid complex called silymarin is believed to be its active component.[2,3] Silibinin (the most active component of silymarin) can inhibit the 5-lipoxygenase pathway (which is involved in the formation of free radicals), scavenge hydroxyl radicals, and inhibit tumor necrosis factor (TNF).[6] Animal models have supported milk thistle’s role as an antioxidant that reduces free radical generation and affects cell growth and apoptosis, thereby reducing inflammation and supporting the liver’s tolerance of oxidative stress, including damage induced by toxins such as carbon tetrachloride.[7-11] The German commission E approves milk thistle for use in the treatment of[12-14]:

Liver conditions including toxin-induced damage and hepatic cirrhosis; and
Milk thistle is one of the most frequently sold herbal products in the United States, with retail sales reaching $8.9 million in 2000, a 14% increase over sales in 1999.[15] It is used in gastroenterology clinics to treat hepatitis and cirrhosis and in oncology settings as a hepatoprotectant to:

Clear toxins;
Assuage symptoms of cancer; and
Improve tolerance to chemotherapy.
The intravenous form of silymarin has also been used as supportive treatment for Amanita phalloides mushroom poisoning.[2,3] Preliminary studies suggest that milk thistle may be potentially beneficial in treating or preventing some cancers[16] for example, it may prove to play a role in any one of the following cancers:

Squamous cell cancer of the tongue;
Colon; and
Of note, a recent dermatologic review examined the use of topical milk thistle as a protectant against ultraviolet (UV) radiation and concluded that it may fall into the category of a botanical cosmeceutical with antioxidant properties that might offset the effects of skin aging and skin cancer.[17]

Milk Thistle for Liver Disease: What Does the Data Support?

Four systematic reviews examined the efficacy of milk thistle for the treatment of liver diseases, in particular, alcoholic liver disease and hepatitis B and C.[18-21] In one review, overall mortality for all chronic liver diseases studied in 14 trials was not reduced and there were no improvements in liver function by histology or biochemical testing that were of clinical significance.[18] The investigators recommended more definitive trials to examine efficacy. In the other reviews, based on high-quality trials, milk thistle did not influence the course of alcoholic or hepatitis B or C disease by outcomes of mortality and histology, but it had the potential to affect liver injury, with improvements seen in liver function tests after acute injury.[19-21]

A recent randomized, placebo-controlled clinical trial assessing the effects of silymarin on acute hepatitis (defined as alanine amino transferase levels higher than 2.5 times normal), mostly due to acute viral hepatitis, used 140 milligrams (mg) of silymarin 3 times daily and reported quicker resolution of symptoms of biliary retention and reduction in indirect bilirubin, but not other LFTs, over 4 weeks.[22] Another recent study suggests that a mixture of Silybum marianum and Aloe vera was protective against carbon tetrachloride-induced acute hepatotoxicity and liver fibrosis.[23]

What to tell your patients. The National Institutes of Health’s National Center for Complementary and Alternative Medicine (NCCAM) provides patient information on the use of milk thistle for hepatitis C.[24] It emphasizes the lack of definitive evidence for its efficacy in treating hepatitis C and urges patients not to replace conventional medical therapy with milk thistle.

Preparations, Dosage, Side Effects, and Contraindications
Milk thistle capsules, tincture, and powder are standardized to contain 70% to 80% silymarin, but different preparations may vary in terms of bioavailability. Chromatographic methods have been used to identify its active ingredients to satisfy Good Manufacturing Practices.[2] It is considered safe at doses up to 1500 mg daily and for treatment durations of up to 41 months.[25] No significant interactions or contraindications have been reported for milk thistle use.[26] Adverse effects are uncommon, with the most commonly reported being mild gastrointestinal disturbance, including a laxative effect.[15]

There is insufficient data on its use in pregnancy and lactation; therefore, it is not recommended for women during these times.[2,3]

Suggested doses in standardized preparations for cirrhosis and acute toxin-induced hepatotoxicity range from 160 to 800 mg daily by mouth. For chronic hepatitis, suggested doses range from 160 to 480 mg daily in silybin equivalents and 420 mg daily in 3 divided doses for silymarin.[2] The preparations Legalon® (containing silymarin), Nature's Way® Thisilyn, and Standardized Milk Thistle Extract Maximum Absorption Formula 2X have been used in clinical trials. Silymarin is also found in some moisturizers for photoaging (for example, RosaCure+ and SkinCeuticals Antioxidant Lip Repair.[17]

In summary, there is ample evidence from animal models for the antioxidant, anti-inflammatory, and antitoxin action of milk thistle, but limited up-to-date clinical evidence from high-quality randomized trials that milk thistle and its components offer significant benefit in the treatment of liver diseases including acute hepatitis and cirrhosis. The clinical benefits that have been demonstrated are of limited magnitude and significance. There are no studies documenting its efficacy in protecting against acute effects of alcohol intoxication or any evidence to suggest that it can reduce one’s appetite for alcohol. A recent review of an integrative medicine strategy for alcohol abuse advocates a balanced holistic approach that includes[1]:

Nutritional counseling;
Healthy lifestyle;
Judicious use of supplementation with B vitamins, probiotics, zinc, and carnitine, as well as botanical products such as milk thistle; and
Acupuncture and mind-body therapy.
Abstinence from alcohol is the key to success in any case of chronic alcohol abuse.

Case Response
Although Mr. Y showed no physical signs or biochemical evidence of alcoholic liver damage at the time of initial presentation, he is at risk for chronic liver disease if his drinking pattern persists or escalates. Because he is motivated to change his approach to drinking, this is an ideal opportunity to move him from 'contemplation' to 'action' on the Prochaska cycle of motivation.[27] His girlfriend could be involved in his future care, and the partnership will help provide the incentives to move him along in small steps to achieve his goal. Since adverse effects of milk thistle are minimal, he may choose it as a supplement to prevent acute alcoholic liver damage during follow-up. When advising Mr. Y, however, the clinician should stress that the evidence for milk thistle's benefits derive from studies on acute viral hepatitis and chronic cirrhosis, and not acute alcohol-induced hepatitis.

There is currently no evidence for a preventive role against liver damage for milk thistle, and using milk thistle is not a substitute for medical care. Follow-up of Mr. Y is essential to ensure progression to abstinence or control of alcohol intake.
The potential for protection against photoaging may be mentioned as a possible benefit of topical milk thistle, although the evidence is preliminary and based mainly on animal studies. Providing the source of evidence for a dermatologic role for milk thistle would be prudent.[17]

HCV Advocate
2010/From HBV Advocate

Milk Thistle Supplements, Taken Orally, Appear IneffectiveSilymarin, found in milk thistle supplements and believed to help prevent liver damage, appears not to be effective when taken orally, but may help damaged livers heal when it is injected intravenously in high doses, according to a Los Angeles Times article that featured Leonard B. Seeff, a hepatitis expert and recently retired senior scientific officer for the National Institute of Diabetes and Digestive and Kidney Diseases

In high doses, silymarin appears to be good for the liver, Seeff said. Studies show that taking large amounts of the compound intravenously can help slow the virus that causes hepatitis C.
But according to experts, when taken orally, silymarin breaks down extremely quickly. In a 2009 study, researchers gave high, 700-mg oral silymarin oral supplements to 32 patients with hepatitis C every eight hours for seven days, which was 10 times more silymarin than most people would get from herbal supplements.

Despite the high dose, the blood levels of silymarin fell far short of levels achieved during intravenous treatment and the treatment had no effect on liver function or health.
If people still want to try a liver supplement, experts recommended a pure milk thistle product without any other herbal additions.

February 2010 HCV Advocate
Lucinda K. Porter, RN
People with chronic hepatitis C virus infection (HCV) who are interested in alternative medicine generally consider milk thistle (silybum marianum). This popular herb is a common ingredient in supplement blends that promote liver health. Researchers have investigated the efficacy of milk thistle and its components for a variety of conditions, including viral hepatitis, type II diabetes, cancer and toxin-removal from the liver.
The BasicsMilk thistle (Silybum marianum) is a plant from the aster family. Silymarin is the active ingredient in milk thistle that is likely responsible for its medicinal qualities. Silymarin is actually a group of flavanoids, with silybin (aka silibinin) being the most powerful. Typically, milk thistle is sold in standardized amounts of 70 to 80% silymarin.
The February 2008 issue of Hepatology looked at milk thistle use among 1145 participants in the HALT-C study, sponsored by the National Institute of Diabetes and Digestive and Kidney Disease, headed by Leonard Seeff. In this HCV study, 44% of the subjects had used herbs at some point, with 23% using them at the time of enrollment. Among all participants, milk thistle was used by 33%, 17% upon enrollment. Although milk thistle users showed similar ALT levels and HCV viral loads to non-users, they showed fewer liver-related symptoms and improved quality of life. Researchers observed that this aspect of the study was uncontrolled and that milk thistle use was self-motivated. They concluded that “a well-designed prospective study can determine whether silymarin provides benefit to persons with chronic hepatitis C.”1
Continue reading before you run out and buy milk thistle. All milk thistle is not alike and what is in the bottle may not match what is promised on the label. In a startling report published by (CL), only one of 10 products passed the necessary tests in order to carry the CL seal of approval.
CL is an independent organization that provides information and testing of nutritional products. They have been around for about ten years. Some information is free, but product reports are available only to subscribers. A one year subscription is $30 and worth every penny.
What caught my attention about the milk thistle testing is that most supplements win CL’s approval. It’s a voluntary program, so presumably manufacturers feel confident enough to submit to testing. The failure of nine out of ten products is extraordinary. One can only imagine the quality of products that don’t agree to testing.
The ResultsTwo of the ten milk thistle products were disqualified for failure to meet the Food and Drug Administration’s (FDA) labeling requirements. Additionally, one of these products had different dosing information from jar to jar, all from the same lot number.
Seven of the remaining eight products did not provide the standardized amount of silymarin although they all claimed to have 80%. Actual amounts were between 47 and 67%. The only product to pass was Jarrow Formulas Milk Thistle. Although the amount of silymarin was not specified on the label, the manufacturer declared that the milk thistle extract contained 80% flavonoids. The actual testing confirmed that Jarrow Formulas Milk Thistle met the minimum industry standard of 70% silymarin.
The HCV Advocate and I do not endorse particular products or treatments. However, it seemed cruel to reveal that only one in ten milk thistle products passed muster without mentioning the name of the product. However, before you run out and buy milk thistle, there are other issues.
First, why didn’t the products pass? ConsumerLabs suggested it was likely due to substandard milk thistle extract, often purchased from Chinese suppliers. Unfortunately, since herbs are not strictly regulated by the FDA, it is virtually impossible to know what is safe and effective.
Second, what is the scientific evidence for or against milk thistle? Why take milk thistle? Is it because you read about it in an article? Did you hear about a study, and if so, what do you know about the research? Or did you wander into your local health food store and ask a sales clerk to recommend something good for the liver.
Third, without specific product information, do you know how much milk thistle to take, what kind, when to take it and when you shouldn’t? Do you know if it interacts with other medications you may be taking? Are there any side effects? Apply the same common sense investigation to dietary supplements as you would to any medicine.
The ResearchWhen it comes to research on dietary supplements and liver disease, milk thistle tops the list. There were 222 milk thistle listings on the U.S. Library of Medicine’s PubMed site dating back to 1952. Although this sounds like a lot of research, compare this to 122,853 listings back to 1957 for interferon. Although research has yet to prove the benefits of milk thistle, it has also not disproved it. This is largely due to inadequate testing or poor scientific methods.
Here are highlights of some current research: The December 2009 issue of Gastroenterology published a French study headed by Ahmed-Belkacem, “Silibinin and Related Compounds Are Direct Inhibitors of Hepatitis C Virus RNA-Dependent RNA Polymerase.” They used a commercially available intravenous preparation of silibinin. This is an encouraging beginning to more research.
According to the U. S. Department of Health and Human Services’ Agency for Healthcare Research and Quality (AHRQ), there is evidence that milk thistle may protect the liver.2 However, the research is unreliable due to poor scientific method, so it’s difficult to sort out the facts.
A search of Germany’s independent, evidence-based Cochrane Library revealed similar observations. According to Rambaldi A, Jacobs BP, and Gluud C “[There is] no evidence supporting or refuting milk thistle for alcoholic and/or hepatitis B or C virus liver diseases. Low-quality trials suggested beneficial effects. High-quality randomized clinical trials on milk thistle versus placebo are needed.”3
Another problem is the test product. AHRQ’s website states, “The largest producer of milk thistle is Madaus (Germany), which makes an extract of concentrated silymarin. However, numerous other extracts exist, and more information is needed on comparability of formulations, standardization, and bioavailability for studies of mechanisms of action and clinical trials.”
If the issue isn’t already complicated, consider this – taken as a supplement, milk thistle is poorly absorbed. After digestion, very little is left for the liver. This is particularly true for older adults. As little as 10% of silymarin may be absorbed in the adult over age 60.
In an article in September 2009 Alternative Medicine Review, biomedical research Parris Kidd, University of California, Berkeley, notes how milk thistle’s most active flavonoid, silybin is poorly absorbed by the body. Kidd states, “silybin-phosphatidylcholine complexed as a phytosome provides significant liver protection and enhanced bioavailability over conventional silymarin.”4 Twenty years ago, an Italian research team reached the same conclusion based on a pharmacokinetic study of nine subjects.5
It all boils down to this – ignoring the lack of scientific research, and choosing to take milk thistle, what product does one buy? Although the Jarrow supplement has been tested by CL, it was not used in clinical research. The one that has been used in research is the Madaus, but it is not available in the U.S. Silybin-phosphatidylcholine, used in various U.S. studies, is available. However, research grade silybin-phosphatidylcholine is not necessarily identical to consumer products.
CautionsTalk to your medical provider before taking milk thistle, particularly if you take other drugs or supplements. Milk thistle is usually well-tolerated. It may have a laxative effect along with other gastrointestinal side effects. Allergic reaction is always a possibility, no matter what you are taking. Theoretically, milk thistle could lower blood sugar levels, so use caution if taking blood sugar-lowering medications. Exacerbation of hemochromatosis has been associated with ingestion of milk thistle.
Milk thistle should not be used by pregnant or breast-feeding women. People with a history of hormone-related cancers, including breast and uterine cancer and prostate cancer, may need to avoid milk thistle.
Since milk thistle is metabolized by the liver, it may interact with other drugs. However, despite earlier warnings about this, evidence of this is flawed. One strategy is to take milk thistle alone rather than in combination with other drugs, particularly oral contraceptives and coumadin. Milk thistle has a short half-life (4 hours).
DosingThe following adult doses are from Natural Standard and are based on clinical research levels:
Silymarin (Legalon®) 230-600 milligrams per day divided into two to three doses
Silipide® (IdB 1016) 160-480 milligrams per day in silybin equivalents
The Bottom Line
Talk to your medical provider before taking milk thistle.
There is no evidence that milk thistle will eliminate HCV.
Milk thistle may provide some benefit to the liver but research has not proved or disproved this.
Milk thistle varies between manufacturers. Do your research before you purchase.
Milk thistle is poorly absorbed by the body, so if you take it, choose a formulation and dose that is bioavailable.
Alcohol extracts should be avoided by anyone with alcohol-related liver disease.
Herbal product use by persons enrolled in the hepatitis C Antiviral Long-Term Treatment Against Cirrhosis (HALT-C) Trial. Seeff LB, Curto TM, Szabo G, Everson GT, Bonkovsky HL, Dienstag JL, Shiffman ML, Lindsay KL, Lok AS, Di Bisceglie AM, Lee WM, Ghany MG. Hepatology. 2008 Feb;47(2):605-12.
Agency for Healthcare Research and Quality. Milk Thistle: Effects on Liver Disease and Cirrhosis and Clinical Adverse Effects. Evidence Report/Technology Assessment no. 21. Rockville, MD: Agency for Healthcare Research and Quality; 2000. 01-E024.
Milk thistle for alcoholic and/or hepatitis B or C virus liver diseases. Rambaldi A, Jacobs BP, Gluud C. Cochrane Database of Systematic Reviews 2007, Issue 4.
A review of the bioavailability and clinical efficacy of milk thistle phytosome: a silybin-phosphatidylcholine complex (Siliphos). Kidd P, Head K. Alternative Medicine Review. 2009 Sep;14(3):226-46.
Pharmacokinetic studies on IdB 1016, a silybin-phosphatidylcholine complex, in healthy human subjects. Barzaghi N, Crema F, Gatti G, Pifferi G, Perucca E. European Journal of Drug Metabolism and Pharmacokinetics. 1990 Oct-Dec;15(4):333-8.


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