Milk Thistle and Silymarin Simply Explained

1. What Is Milk Thistle (Silymarin)?

Milk thistle is a thistle-like plant. An extract called silymarin is obtained from its ripe fruits. Silymarin is a mixture of several plant substances. Traditionally, the plant is used for discomfort in the upper abdomen and in connection with the liver.

2. Where Is It Found, and What Is It Made From?

Milk thistle grows in dry, sunny locations. Farmers cultivate it for its fruits. The ripe fruits are used. The extract is made from them. In studies, mainly standardized extracts, the single substance silibinin, and a complex with phosphatidylcholine were examined.

3. What Does Milk Thistle (Silymarin) Do? What Research Shows

Liver Values During Drug Treatment

With tuberculosis drugs, silymarin lowered the risk of liver damage in a summary of several studies 10. A small study confirmed lower liver values after two weeks 29. For liver damage from drugs overall, a larger summary found no confirmed effect 2. With chemotherapy and the MS drug fingolimod, liver values were more favorable with silymarin than with sham treatment 20212733. In children undergoing chemotherapy, a traditional fruit infusion lowered liver values more than silymarin 22.

Non-Alcoholic Fatty Liver Disease

In non-alcoholic fatty liver, several studies found lower liver values in the blood 2316. A summary also showed fewer blood lipids and less fat accumulation in liver tissue 3. In fatty liver inflammation (NASH), the liver tissue did not improve in a study with sham treatment 23. The results are based mainly on blood values. The preparations and doses were very different.

Diabetes and Blood Glucose

A summary of many studies found lower blood sugar, less insulin, and a better long-term blood sugar 5. However, a study with a standardized extract found no difference in blood sugar and long-term blood sugar 26. Mixtures with other substances lowered blood sugar, but this applies only to the respective mixture 141525. The preparations and doses were different.

Chronic Hepatitis

In chronic hepatitis, a standardized extract improved liver values 2. A controlled study (with a comparison group) found a greater reduction in liver values with silymarin plus standard therapy 32. In hepatitis C, silymarin acted equally against the virus compared with the alga spirulina, but lowered liver values less 24. The data situation is inconsistent.

Liver Cirrhosis

In liver cirrhosis, a review found lower liver values in three of six studies 13. A study in chronic liver diseases found no difference in complications 32. It remains open whether silymarin has a noticeable benefit in cirrhosis. The forms studied were different.

Cancer (Silibinin)

On cancer, only observational data are available. A case series (description of several individual cases) reports better tolerability with silibinin 36. An observational study found a better response to cancer treatment with a mixture containing silibinin, but no confirmed advantage in survival 37. Review articles are based predominantly on laboratory and animal experiments 4041. Data on whole fruits or tea are lacking.

Death Cap Mushroom Poisoning

On death cap mushroom poisoning, there are no controlled studies. An evaluation of case reports found higher survival rates with silibinin or penicillin 11. In definitely confirmed poisoning, no confirmed difference between the treatments could be shown 11. An observational study with oral silymarin found no differences 35. The data come predominantly from uncontrolled observations.

Other Investigations

In this area, very different endpoints (target value of the study) were examined. Controlled studies found less oxidative stress 2728. After a bypass operation, the inflammation marker CRP was lower with silymarin 31. In cases of oxygen deficiency, silymarin lowered the liver values more than placebo (sham treatment) 30. Many results are based on small studies, some without allocation by lot.

4. How Was Milk Thistle (Silymarin) Taken in the Studies?

In the studies, predominantly standardized silymarin extracts were examined. Silibinin as a single substance, a complex with phosphatidylcholine, and silibinin-containing infusions were also studied. Larger studies on whole or ground fruits as tea or powder are lacking. Many studies examined combination preparations with other ingredients. Their results apply only to the respective mixture, not to silymarin alone.

5. Is Milk Thistle (Silymarin) Safe? Side Effects in the Studies

The tolerability of silymarin is predominantly described as good. Mostly only few, mild complaints were reported, such as gastrointestinal reactions or insomnia 913171921. However, a summary of studies on fatty liver found side effects more frequently, especially gastrointestinal complaints 4. With simultaneous intake of anticoagulants, a possible bleeding risk is described 18.

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