Product Review: Milk Thistle Supplements

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Product Review: Milk Thistle Supplements

Initial Posting: 12/2/09 Last Update: 1/8/10

Sections: Jump to a section by clicking on its name.What It IsWhat It DoesQuality Concerns and What CL Tested ForWhat CL FoundTest Results by ProductWhat to Consider When BuyingWhat to Consider When UsingConcerns and CautionsFull list of Ingredients by ProductHow Products Were Evaluated

What It Is:

The ripe seeds of the milk thistle plant (Silybum marianum) are used medicinally. One of the most important constituents of milk thistle is silymarin, which itself has of several chemical constituents, the most prominent of which is silybinin (silybin).

What It Does:

Diabetes

The silymarin component of milk thistle may decrease blood sugar, hemoglobin A1c, and LDL cholesterol levels when used with conventional therapy in people with type 2 diabetes. It has also been shown to reduce insulin resistance in people with coexisting diabetes and alcoholic cirrhosis.

Diseases of the Liver

Silymarin is thought to act as a liver-protectant. However, evidence of benefit in liver disease has been mixed.

One preliminary study of a specific silybinin preparation improved liver function in people with chronic active hepatitis. However, most studies in patients with hepatitis B or C have generally not shown an improvement in mortality or liver function using milk thistle or preparations of milk thistle. Similarly, in alcoholic liver disease, some preliminary clinical studies suggested that milk thistle might improve liver function and mortality. However, an analysis of several studies did not show a significant effect.

Liver protection from chemotherapy and other drugs

Preliminary evidence suggests that milk thistle extract standardized to 70% - 80% silymarin may protect the liver against damage from certain toxins, including drugs such as acetaminophen and phenytoin (Dilantin).

A recently published study (Ladas, Cancer 2010) suggests that milk thistle extract may reduce liver toxicity due associated with chemotherapy. Liver toxicity is often a complication of chemotherapy and limits therapy. The study was conducted on children with acute lymphoblastic leukemia (ALL) receiving maintenance chemotherapy. Milk thistle extract standardized to 33% silibinin was given at a daily dose of 80 mg to 320 mg of silybinin. Milk thistle was associated with reductions in levels of liver enzymes that indicate toxicity. Interestingly, a benefit was not seen during the short course of therapy (28 days) but one month later.

Administered intravenously (IV), silybinin may lessen liver damage due to poisoning by Amanita phalloides mushroom (death cap) — although this IV preparation is not readily available in the U.S.

Other:

Silybinin is under investigation for use in preventing or treating various forms of cancer, especially prostate cancer.

For information about dosage, see What to Consider When Using section.

Quality Concerns and What CL Tested for:

Most clinical studies of milk thistle's effectiveness have used specific dry extracts standardized to approximately 70% - 80% silymarin on a weight basis. ConsumerLab.com purchased and tested milk thistle products to determine which extracts on the market contained this level of silymarin. Milk thistle is also available in non-concentrated, seed powder form containing at least 1.5% silymarin.

All products were also tested for lead contamination, as this can occur in herbal supplements. Tablet and caplet products were additionally tested for their ability to properly break apart for absorption. Liquid products and standard capsules do not undergo this testing, as they will quickly release their contents.

What CL Found:

Ten milk thistle supplements were selected for testing. Two products, 1Fast400 Milk Thistle and Pure Milk Thistle (Pharmex), failed to meet the FDA labeling requirement of indicating the part of the milk thistle plant used (typically seed) and, consequently, were disqualified from further review. Labeling on 1Fast400 Milk Thistle was also found to be inconsistent from jar to jar from the same lot: a one-quarter teaspoon serving was listed to provide 600 mg of milk thistle extract on one jar but 560 mg on another jar.

Among the remaining eight supplements tested, seven failed to provide the standardized amount of silymarin listed on the respective labels. Each of the following products claimed to provide an extract that was 80% silymarin, but the silymarin content was found to actually be much lower:

Enzymatic Therapy™ Milk Thistle X — 52% silymarinFinest Natural Milk Thistle — 47% silymarinNatural Factors Milk Thistle — 67% silymarinNature's Plus Herbal Actives Milk Thistle — 62% silymarinSmart Basics Milk Thistle Extract — 52% silymarinWhole Foods™ Milk Thistle — 54% silymarin

Nutrilite Milk Thistle And Dandelion was found to contain enough silymarin to meet its claim of an 80% silymarin milk thistle extract. However, it also claimed to contain 76 mg of a “silybin extract complex,†but no additional silybin was found in the product to support this claim.

The only product to be approved for quality was Jarrow Formulas Milk Thistle. This product claimed to provide a milk thistle extract that was 80% flavonoids – the larger family of compounds which includes silymarin. As the amount of silymarin was not specified, ConsumerLab.com held the product to an industry minimum standard of 70% silymarin, and the product met this standard.

Why do the vast majority of products fail to provide their claimed levels of silymarin?

A likely explanation is that the milk thistle extract purchased to make these products is substandard. Some Chinese ingredient suppliers sell a less expensive, substandard form of milk thistle extract known as “80% silymarin – UV-vis.†This name implies that if analyzed with the "UV-vis" test method, the test will show 80% silymarin. However, the UV-vis test method is not specific to silymarin, i.e., it counts compounds that are notsilymarin as being silymarin.

If the same ingredient were tested with a more specific and accurate test method, e.g., the HPLC method used by ConsumerLab.com, the actual silymarin content may be revealed as being significantly lower than 80%, as seen in this Review. Suppliers charge a higher price for exact that is "80% silymarin – HPLC." However, the FDA does not set standards for the composition of herbal products or how manufacturers are supposed to test them. Consequently, manufacturers may choose to use any form of milk thistle and consumers normally have no way to knowing the quality of what they are buying.

Does it matter if you use a product with less silymarin?

It is possible that the efficacy of milk thistle extract may be affected by lower silymarin levels. Clinical studies have tended to use a range of 400 to 600 mg per day of milk thistle extract, standardized to 70% – 80% silymarin. This would provide about 300 – 450 mg of silymarin per day. In this Review, the amounts of silymarin actually found in the products at their suggested daily serving sizes yielded anywhere from about 100 to 1,000 mg of silymarin. For more information about this see the ConsumerTips™ section.

None of the products was found to be contaminated with lead. One product was sold in tablet form and, therefore, underwent disintegration testing: It passed this analysis, showing that it broke apart properly (disintegrated) in solution - which is necessary for ingredients to be absorbed.

Test Results by Product:

Listed alphabetically below are reviews of ten milk thistle products selected by ConsumerLab.com. The full list of ingredients for each product is available by clicking on the word "Ingredients" in the first column. Products listed as "Approved" met their label claim and ConsumerLab.com's standards for milk thistle products (See Passing Score).

RESULTS OF CONSUMERLAB.COM TESTING OF MILK THISTLE SUPPLEMENTS

Click on beneath a product name to find a vendor that sells it.

To find retailers that sell some of the listed products click here.Product Name, Claimed Amount and Type of Milk Thistle per Unit, Standardized Level of Silymarin, and Suggested Dose on Label

Click on "Ingredients" for Full Listing

Company

(Dist. =

Dist-

ributor

Mfd. =

Manu-

facturer)

Claimed or Minimum Expected Amount of Silymarin Per Daily Serving Suggested on Label (mg)OVERALL RESULTS:

APPROVED

(Passed)

or

NOT

APPROVED

(Failed)

(See How Products Were Evaluated)Contained Claimed or Minimum Expected Amount of Silymarin

If Claimed Amount Not Found, Actual % of Silymarin in Claimed Amount of Extract (%wt/wt)Did Not Exceed Contamin-

ation Limit

for Lead

Disintegrated

Properly

(NA = Not

Applicable)

1Fast400 Milk Thistle 80% 125 Grams (amount of extract variable [80% silymarin] per ¼ teaspoon, daily dose unclear)

IngredientsDist. by 1Fast400Claimed different amount of ingredient per ¼ teaspoon on products within same lot:

“600 mg yielding 480 mg†or “560 mg Milk Thistle Extract 80%â€NOTAPPROVED

Inconsistent labeling1Not tested

Not tested

Not tested

Enzymatic Therapyâ„¢ Milk Thistle Xâ„¢ (150 mg extract [80% silymarin] per capsule, 6 per day)

IngredientsMfd. by Enzymatic Therapy, Inc.720 mg

NOTAPPROVEDOnly found 65% of claimed silymarin

Silymarin in extract: 52%

NA

Finest Natural® Milk Thistle (175 mg extract [80% silymarin] per capsule, 2 to 3 per day)

Ingredients

Dist. by Walgreens Co.280 - 420 mg

NOTAPPROVEDOnly found 59% of expected silymarin

Silymarin in extract: 47%

NA

Jarrow Formulas® Milk Thistle (150 mg extract [80% total flavonoids] per capsule, 1 to 3 per day)

Ingredients

Mfd. by Jarrow Formulas®105 – 315 mg

(Based on minimum expectation of 70% silymarin in extract)

APPROVED

NA

Natural Factors® Milk Thistle (250 mg extract [80% silymarin] per capsule, 3 to 6 per day)

Ingredients

Mfd. by Natural Factors Canada600 - 1,200 mg

NOTAPPROVEDOnly found 84% of expected silymarin

Silymarin in extract: 67%

NA

Nature's Plus® Herbal Actives Milk Thistle (500 mg extract [80% silymarin] per extended release vegetarian tablet, 1 per day)

IngredientsMfd. by Natural Organics Laboratories, Inc.400 mg

NOTAPPROVED

Only found 77% of expected silymarin

Silymarin in extract: 62%

NA

Nutrilite® Milk Thistle and Dandelion (156 mg extract [80% silymarin] and 76 mg silybin extract complex per tablet, 2 per day)

IngredientsDist. by Access Business Group International LLC249.6 mg silymarin and silybin extract; silymarin contribution from silybin extract unknown

NOTAPPROVEDFound amount claimed for milk thistle extract but not for the silybin extract complex

Pure Milk Thistle (450 mg extract [80% silymarin] per vegetarian capsule, 3 per day)

Ingredients

Mfd. by Pharmex LLC1,080 mg

NOTAPPROVED

Did not list plant partNot tested

Not tested

Not tested

Smart Basics Milk Thistle Extract (300 mg extract [80% silymarin] per capsule, 1 per day)

IngredientsDist. by Vitacost.com240 mg

NOTAPPROVEDOnly found 70% of claimed silymarin

Silymarin in extract: 56%

NA

Whole Foodsâ„¢ Milk Thistle (100 mg extract [80% silymarin] per capsule, 4-6 per day)

IngredientsDist. by Whole Foods Market320 - 480 mg

NOTAPPROVED

Only found 68% of expected silymarin

Silymarin in extract: 54%

NA

1 Products purchased from the same lot had different labels including different supplemental facts panels. The plant part was also absent from one label.Unless otherwise noted, information about the products listed above is based on the samples purchased by ConsumerLab.com (CL) for this Product Review. Manufacturers may change ingredients and label information at any time. So be sure to check labels carefully when evaluating the products you use or buy. If a product's ingredients differ from what is listed above, it may not necessarily be the same as what was tested.

The information contained in this report is based on the compilation and review of information from product labeling and analytic testing. CL applies what it believes to be the most appropriate testing methods and standards. The information in this report does not reflect the opinion or recommendation of CL, its officers or employees. CL cannot assure the accuracy of information provided to it by third parties. Liability to any person for any loss or damage caused by errors, omissions, or inaccuracies in this report is hereby disclaimed.Copyright ConsumerLab.com, LLC, 2009. All rights reserved. Not to be reproduced, excerpted, or cited in any fashion without the express written permission of ConsumerLab.com LLC.

ConsumerTipsâ„¢:

What to Consider When Buying:

Extracts vs. Seed Powder:

Dry milk thistle seed powder contains only 1.5% to about 3.0% silymarin, while dry "extracts" are much more concentrated — with silymarin accounting for approximately 70% to 80% of their weight. Consequently, pills made from seed powder contain about 9 to 15 mg of silymarin, while pills made from dry extracts contain approximately 112 mg to 240 mg of silymarin, depending on the size of the pill. Be aware, however, that "liquid extracts" are not necessarily concentrated extracts. One liquid extract product tested in a previous Review indicated that it was made from milk thistle "seed" as opposed to a "seed extract." Products like this are not concentrated — this particular product was expected to contain only 7.5 mg of silymarin per mL (although testing showed it to actually provide less than 2 mg). People who prefer to use whole herb products as opposed to concentrated extracts should be aware that much larger doses of milk thistle will be necessary to get the same amount silymarin.

Keep in mind that products can vary widely in the amount of extract claimed to be in each unit. For example, among products evaluated in this Review the amount of milk thistle extract claimed per capsule or tablet ranged from 100 mg (Whole Foods) to 500 mg (Nature’s Plus). And serving recommendations also range widely.

What to Consider When Using:

The common dosage of milk thistle is 200 mg 2 to 3 times a day of an extract standardized to 70% to 80% silymarin. For diabetes, the 200 mg is taken 3 times a day along with conventional treatment. For cirrhosis of the liver, a daily dose of 420 mg has been used (expected to contain about 300 to 330 mg of silymarin). For chronic active hepatitis, 240 mg of silybinin (the major constituent of silymarin) taken twice daily has been used. (Among the products tested in this review, silybinin was generally found to account for 45% to 65% of the total silymarin.) There is some evidence that preparations containing phosphatidylcholine may increase absorption of active ingredients of milk thistle.

As a liver-protectant during chemotherapy, milk thistle extract providing 80 mg to 320 mg of silibinin per day has been used in children, with the dosage based on weight (approximately 5.1 mg of silibinin daily per kilogram of body weight) (Ladas, Cancer 2010).

For treatment of mushroom poisoning with Amanita phalloides, 20 mg to 50 mg of silybinin per kg of body weight has been administered intravenously over 24 hours, divided into four infusions, each administered over a two hour period. Intravenous silybinin, however, is not available in the U.S.

Additional information about clinical studies with milk thistle is found in the Natural Products Encyclopedia on this website.

Concerns and Cautions:

Milk thistle and its extracts are generally well-tolerated but, infrequently, can have a laxative effect and cause other gastrointestinal side-effects.

Some patients may have allergic reactions to milk thistle including itching, rash, hives, eczema, and anaphylaxis. Allergic reactions may be more likely to occur in patients sensitive to plants such as ragweed, chrysanthemums, marigolds, and daisies.

Although drug interactions have not been reported, milk thistle might reduce the effectiveness of oral contraceptives and it might inhibit cytochrome P450 2C9, increasing the levels of certain drugs metabolized by it such as amitriptyline, diazepam, verapamil, and warfarin.

To further assist consumers, ConsumerLab.com licenses its flask-shaped CL Seal of Approved Quality (see The CL Seal) to manufacturers for use on labels of products that have passed its testing. ConsumerLab.com will periodically re-evaluate these products to ensure their compliance with ConsumerLab.com's standards.