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NCCIH Clinical Digest

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Hepatitis C and Dietary Supplements:
What the Science Says

May 2013

Milk Thistle

Milk thistle (scientific name Silybum marianum) is a plant from the aster family. Silymarin is an active component of milk thistle believed to be responsible for the herb’s health-related properties. Milk thistle has been used in Europe for treating liver disease and jaundice since the 16th century. In the United States, silymarin is the most popular dietary supplement taken by people with liver disease.

Strength of Evidence

  • Much research supports the conclusion that there little evidence of benefit for milk thistle as a treatment for hepatitis C.

Research Results

  • A 2012 controlled clinical trial, cofunded by NCCAM and NIDDK, showed that two higher-than-usual doses of silymarin were no better than placebo in reducing the high blood levels of an enzyme that indicates liver damage. In the study, 154 people who had not responded to standard antiviral treatment for chronic hepatitis C were randomly assigned to receive 420 mg of silymarin, 700 mg of silymarin, or placebo three times per day for 24 weeks. At the end of the treatment period, blood levels of the enzyme were similar in all three groups.
  • Results of the HALT-C study suggested that silymarin use by hepatitis C patients was associated with fewer and milder symptoms of liver disease and somewhat better quality of life, but there was no change in virus activity or liver inflammation. The researchers emphasized that this was a retrospective study (one that examined the medical and lifestyle histories of the participants). Its finding of improved quality of life in patients taking silymarin was not confirmed in the more rigorous 2012 study described above.
  • A 2009 Cochrane systematic review assessed the beneficial and harmful effects of milk thistle in patients with alcoholic liver disease and/or hepatitis B or C liver diseases and found that there is not enough high-quality evidence to support the use of this intervention.


  • Available evidence from clinical trials in people with liver diseases suggests that milk thistle is generally well-tolerated.
  • Side effects can include a laxative effect, nausea, diarrhea, abdominal bloating and pain, and occasional allergic reactions.
  • In NIH-funded studies of silymarin in people with hepatitis C that were completed in 2010 and 2012, the frequency of side effects was similar in people taking silymarin and those taking placebos. However, these studies were not large enough to prove that silymarin is safe for people with chronic hepatitis C.

Other Supplements

Other supplements have been studied for hepatitis C, but overall, no benefits have been clearly demonstrated.


Probiotics are live microorganisms that are intended to have a health benefit when consumed.

Strength of Evidence

  • Only a few studies have examined the effects of probiotics on hepatitis C.

Research Results

  • Research hasn’t produced any clear evidence that probiotics are helpful in people with hepatitis C.


  • Most people can use probiotics without experiencing any side effects—or with only mild gastrointestinal side effects such as intestinal gas —but there have been some case reports of serious adverse effects in people with underlying serious health conditions.


Strength of Evidence

  • Preliminary studies, most of which were conducted outside the United States, have examined the use of zinc for hepatitis C.

Research Results

  • Zinc supplements might help to correct zinc deficiencies associated with hepatitis C or reduce some symptoms, but the evidence for these possible benefits is limited.
  • A few preliminary studies have looked at the effects of combining supplements such as lactoferrin, SAMe, or zinc with conventional drug therapy for hepatitis C. The evidence is not sufficient to draw clear conclusions about benefit or safety.


  • Zinc is generally considered to be safe when used appropriately, but it can be toxic if taken in excessive amounts.


Glycyrrhizin (or glycyrrhizic acid) is a compound found in licorice root.

Strength of Evidence

  • Glycyrrhizin has been tested in only a few clinical trials in patients with hepatitis C.

Research Results

  • There is currently not enough evidence to determine if glycyrrhizin is helpful for hepatitis C.


  • In large amounts, glycyrrhizin or licorice can be dangerous in people with a history of hypertension (high blood pressure), kidney failure, or cardiovascular diseases.

Colloidal Silver

Colloidal silver consists of tiny silver particles suspended in liquid. Colloidal silver products are often promoted for treating various diseases, including hepatitis C.

Strength of Evidence

  • Scientific evidence does not support the use of colloidal silver to treat any disease, and serious, irreversible side effects can result from its use.

Research Results

  • There is currently no research to support its use for hepatitis C.


  • Colloidal silver is known to cause serious side effects, including a permanent bluish discoloration of the skin called argyria.

NCCIH Clinical Digest is a service of the National Center for Complementary and Integrative Health, NIH, DHHS. NCCIH Clinical Digest, a monthly e-newsletter, offers evidence-based information on complementary health approaches, including scientific literature searches, summaries of NCCIH-funded research, fact sheets for patients, and more.

The National Center for Complementary and Integrative Health is dedicated to exploring complementary health products and practices in the context of rigorous science, training complementary health researchers, and disseminating authoritative information to the public and professionals. For additional information, call NCCIH's Clearinghouse toll-free at 1-888-644-6226, or visit the NCCIH Web site at NCCIH is 1 of 27 institutes and centers at the National Institutes of Health, the Federal focal point for medical research in the United States.


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This page last modified May 16, 2013