Milk Thistle for Pets: An Effective Natural Treatment?

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How Long Does It Take for Milk Thistle to Work?

Find out the many uses of milk thistle, as well as factors that can determine how long someone may need to take milk thistle for it to work and do its job.

Milk thistle may improve the way the hepatic system works when injured, diseased or under chronic toxic overload. Reviews of the literature on efficacy and treatment duration are often contradictory as to time vs. effectiveness of treatment due to study design and milk thistle formulations used. However, overwhelming small clinical trials exist to show the effectiveness of milk thistle on the support of liver related diseases including those involving blood sugar problems or cancer (1, 2) regardless of study design duration.

Milk thistle has also been used for:

  • treatment of high cholesterol levels
  • diabetes
  • gall bladder problems
  • in prostate and breast cancer
  • and as an immune modulator (1).

What Are the Functions of Milk Thistle?

Milk thistle (silymarin) affects health primarily through its antioxidant abilities. Silymarin (milk thistle) acts as a free radical scavenger and modulates the enzymes that cause liver cellular damage, fibrosis and cirrhosis. By decreasing cellular oxidative stress and cytotoxicity, silymarin protects those liver cells that have not been damaged irreversibly (2).

What Conditions Are Treated by Milk Thistle?

Approximately 2 million people a year die of liver disease with few treatments for these conditions other than lifestyle. The therapeutic attention on the use of milk thistle for liver disease has received a great deal of attention in the past 20 years due to its well-documented antioxidant and liver-protecting effects in conjunction with an excellent safety profile.

Milk thistle is currently used for the treatment of toxin-induced liver injury, for its inhibition of progressive hepatic fibrosis and the prevention of cirrhosis, for its antifibrogenic effects in alcohol-induced cirrhosis and for modulation of insulin resistance.

Milk thistle is most often used in liver cirrhosis/alcohol – related liver disease, nonalcoholic fatty liver disease, non-alcoholic steatohepatitis (NASH), the ingestion of toxic amatoxin mushrooms, radiation mucositis and liver damage from the ingestion of toxic chemicals (2, 3).

Factors that Affect Duration of Treatment

Bioavailability of the formulation used is paramount both in study results and clinical endpoints obtained for the dosage given. Reviews of studies may show little effect from small doses but statistical effects from large doses and the form of milk thistle may have made a difference in the amount needed to make a statistical change (1, 4).

Oral administration of silymarin has a low bioavailability by itself, but when complexed with phosphatidylcholine and/or β-cyclodextrin it has been shown that the solubility improves – thus providing the potential of having a therapeutic effect at lower doses and/or shorter lengths of treatment time.

The state of liver damage and effectiveness is also correlated. The timing of delivery of milk thistle is imperative with earlier interventions faring better (4).

Standardizing the milk thistle extract to silybin, the most biologically active component in milk thistle, also makes a positive difference in treatment duration.

Dosage and Duration of Milk Thistle Therapy

Using the most bioavailable form of milk thistle or silybin, studies have shown the usual dosage to be 420 mg in three divided doses. The doses are divided due to the short half-life of the herb.


A review of the literature shows a response to silybin + phospholipids in nonalcoholic fatty liver disease (NAFLD) patients in 6 months with improvements in insulin resistance, liver enzymes and the degree of steatosis noted as well (4).

Liver Cirrhosis/Alcohol-Related Liver Disease

In one study the four-year survival rate was significantly higher (58% vs. 39%) in silymarin recipients as opposed to the placebo group with a treatment period of at least 24 months and an observation period of 4 years. A review of clinical data across five studies showed a pooled liver-related mortality rate of 4.9% in the silymarin group compared with 9.3% in the placebo group (2).

Viral Hepatitis

Studies suggest that silymarin should be approved for liver support, not for treatment of viral hepatitis. Baseline use was associated with significantly less histological damage in patients with chronic hepatitis C in a cohort of 177 Egyptian patients over a 12-month period of time and an increase in quality of life scores (2).

Liver Enzymes

Other studies show a preliminary decrease in liver enzymes in alcoholic liver disease at four weeks with the significance of the decrease in liver enzymes unknown (2). In other words, the blood samples were not correlated with histological data or other liver function tests.

Oxidative Stress Patterns

Improvement in oxidative stress parameters was consistently noted at six months’ duration of treatment with a specialized milk thistle delivery system (2). Improvement in oxidative stress patterns is responsible for improved insulin-signaling and liver cell functioning.

Blood Glucose and Insulin Levels

Some studies show no improvement in fasting blood glucose levels at three months but show improved values in HBA1C only. And in another study at six months, adequate insulin production was enabled to lower fasting blood glucose levels by 10% when compared with placebo in Type 1 diabetics (3). These results not only highlight the inconsistency but point towards a potential deeper clinical response with a longer duration of treatment.


Treatment for NASH has shown positive results at 90 days with improvement in biometric parameters such as change in BMI and liver lobe size at 48 weeks after being treated with 2100 mg/day of silymarin. The 48 weeklong treatment at such a high dosage yielded improvements in liver histology, noninvasive markers of hepatic fibrosis and liver function parameters vs. baseline with silymarin but not with placebo (2).

Oxidative stress is the key pathogenic ingredient in NASH, and treatment with silymarin and its strong antioxidant capabilities and ability to stimulate glutathione all work towards recovery of the liver cell. Preventive lifestyle changes remain the treatment of choice but are not the chosen option of some.

Drug Induced Liver Toxicity

The treatment of drug induced liver toxicity met with controversy with study results dependent on the ability of milk thistle to lower superoxide dismutase, an enzyme that breaks down toxic molecules. According to the literature, prophylactic therapy reduced the possibility of developing drug induced liver toxicity more effectively than it treated it after the fact. Contrarily, a German study showed that silymarin improved quality of life scores (i.e. fewer cases of vomiting and nausea) and lowered liver enzyme levels after two months of treatment in patients already injured from toxin exposure (2).


Taking a specific extract of milk thistle and other herbs (Iberogast) taken orally for four weeks (1 ml 3x day) seemed to relieve the severity of acid reflux, epigastric pain, cramping, nausea and vomiting compared to placebo (3).

Other Disorders

A human trial containing 420 mg in 3 divided doses for 12 weeks was effective on a study of thalassemia patients, and most clinicians agree that taking milk thistle in addition to iron chelation therapy is more effective than chelation therapy alone (5). A combination of milk thistle, diet and exercise reduced cholesterol by 33.6 mg/dl compared to diet and exercise alone at 12 months. While milk thistle is used for other conditions, most human trials that show effectiveness run for several weeks (5) and most need more human data.

While effects on some parameters may be seen in weeks, more than likely, chronic conditions will need to be treated for several months to achieve the best outcome. Duration of treatment of up to 41-48 weeks is considered safe (2, 5).

Absorption Parameters

Milk thistle should be taken 30 minutes prior to a meal for maximum absorption. Consumption in the form of tea is not recommended as it is poorly soluble in water. Solubility is increased when combined with phosphatidylcholine.

Natural Wellness’s UltraThistle contains a patented, highly-absorbable form of milk thistle called Silybin Phytosome. Silybin Phytosome combines silybin – the most active and beneficial ingredient in milk thistle which is responsible for 50% to 70% of milk thistle’s therapeutic benefit – at a molecular level with phosphatidylcholine, a phospholipid which is the same material found in cell membranes.


The duration of therapy is inconsistently documented in the literature most probably due to the different bioavailability’s of the formulas used in the older studies, poor study design and low methodological quality (3).

Variations in factors affecting need for treatment duration also should be considered such as:

  • degree of liver cell damage at start of treatment
  • complications from lack of blood sugar control
  • presence or absence of cancer
  • presence of ongoing toxin exposure
  • and bioavailability of product being used.

Degree of effectiveness relative to treatment duration is unclear in the literature but seems to have deeper functional meaning for chronic disease and longer-term use of a standardized extract of silybin mixed with phospholipids.

  1. Kaur, A.K. (2011). Milk thistle: A review. International Journal of Pharma. Research and Development-Online (IJPRD), 3(2):1-10. Retrieved from,23
  2. Gillessen A., H. Hartmut and Schmidt, J. (2020). Silymarin as supportive treatment in liver diseases: A narrative review. Adv Ther. Retrieved from
  3. Silybum marianum, synonym Cardus marianum. (n.d). TRC Natural Medicines. Retrieved 3/9/2020 from,-herbs-supplements/professional.aspx?productid=138#scientificName
  4. Kuhu, R. and Iyer U. (2019). Role of silymarin in the management of non-alcoholic fatty liver disease: Time to clear the mist. Functional Foods in Health and Disease, 9(5):126-133. Retrieved from DOI: 10.31989/bchd.v2i5.622
  5. Milk thistle. (2019, March 1). Retrieved 3/12/2020 from
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About the Author

Kathy Shattler, BS, MS, RDN

Kathy Shattler has been a Registered Dietitian for over 25 years and currently runs her own Telehealth Clinic while freelance writing in her spare time. She graduated with a Master of Science degree in Human Nutrition from Michigan State University and has a plethora of experience in both clinical nutrition as well as public health. She has been deemed a trailblazer in her profession and continues to strive for excellence in public health education in integrative medicine.

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