Product Reviews
Milk Thistle and Liver Formula Supplements Review

HereInitial Posting: 7/1/2016  Last update: 10/22/2018Milk Thistle and Liver Formula Supplements Reviewed by

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Summary: What You Need to Know About Milk Thistle Supplements
  • Milk thistle may help to protect the liver from certain toxins -- including drugs such as acetaminophen and phenytoin (Dilantin). There is mixed evidence it may improve liver function in people with chronic active hepatitis. It may also decrease blood sugar, hemoglobin A1c, and LDL cholesterol levels when used with conventional therapy in people with type 2 diabetes (see What It Does).
  • Silymarin, a compound in milk thistle, is thought to responsible for some of the herb's effects (see What It Is).
  • Eight of the ten milk thistle supplements selected for testing failed because they contained less silymarin than claimed or expected (see What CL Found).
  • Among four products Approved for Quality by (including two Approved in CL's Quality Certification Program), two were chosen as Top Picks >>
  • Milk thistle comes in various forms and concentrations, but most clinical studies of milk thistle's effectiveness have used specific extracts standardized to approximately 70% - 80% silymarin at a dose of about 200 mg taken 2 to 3 times per day (see What to Consider When Buying and Using for dosage and other details).
  • Milk thistle is generally well-tolerated but, infrequently, can have a laxative effect or other gastrointestinal side-effects. Allergic reactions can occur, especially in people who are sensitive to certain plants and it may interact with certain medications (see Concerns and Cautions).
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 several chemical constituents, the most prominent of which is silybinin (also referred to as silibinin or silybin).

What It Does:
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.

Hepatitis and Diseases of the Liver
Silymarin is thought to act as a liver-protectant, although 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 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, but later 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). Milk thistle extract may also reduce liver toxicity associated with chemotherapy -- a complication which can limit therapy. In a study of children with acute lymphoblastic leukemia (ALL) receiving maintenance chemotherapy, milk thistle extract standardized to 33% silybinin was given at a daily dose of 80 mg to 320 mg of silybinin (Ladas, Cancer 2010). Although no benefit was seen during the short course of therapy (28 days), one month later the milk thistle treated children had reductions in levels of liver enzymes that indicate toxicity compared to those who did not receive milk thistle.

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.

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

Additional information about clinical studies with milk thistle is found in the Natural Products Encyclopedia on For information about dosage, see What to Consider When Using section below.

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. Milk thistle is also available in non-concentrated, seed powder form containing at least 2% silymarin. purchased and tested milk thistle products to determine which products contained this level of silymarin -- and/or other levels if claimed on labels.

Past testing by has revealed many milk thistle products which do not contain these expected amounts. All products were also tested for contamination with the heavy metals lead, cadmium and arsenic, as this can occur in herbal supplements — although is less likely with extracts. 

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