What is Milk Thistle and Does it Affect Patients with Asthma?

A 56-yo male with severe asthma and cirrhosis due to hepatitis C takes milk thistle (Silybum marianum) for his liver disease. He is on maximal asthma therapy including ICS plus LABA, LTRA and prednisone 5 mg po qd. His pulmonologist is wondering if his milk thistle intake has anything do to with his difficult to control asthma.

What is milk thistle?

Thistle is the common name of a group of flowering plants characterized by leaves with sharp prickles on the margins. Prickles often occur all over the plant and are an adaptation to protect the plant against herbivorous animals, discouraging them from feeding on the plant.

The national flower of Scotland is Scots Thistle possibly stemming from the story that a Viking attacker stepped on one at night and cried out, so alerting the defenders of a Scottish castle.

Milk thistles are thistles of the genus Silybum Adans., flowering plants of the daisy family. They are native to the Mediterranean regions of Europe, North Africa and the Middle East. Health uses, mainly for chronic liver disease, have been traditionally claimed for the plant.

What is the therapeutic use of milk thistle?

Milk thistle has been used medicinally for over 2,000 years, most commonly for the treatment of liver and gallbladder disorders. The active compound in milk thistle is silymarin, a mixture of at least 4 flavonolignans. The terms "milk thistle" and "silymarin" are often used interchangeably. Silymarin is typically administered orally in amount ranging from 200-500mg per day.

Uses based on scientific evidence rated by grade:

Chronic hepatitis

Several studies of oral milk thistle reported improvements in LFTs. Most studies were small and poorly designed.
Grade B


In several studies from Europe milk thistle improved LFTs and decreased death rate.
Grade B

Acute viral hepatitis

Not recommended.
Grade C

Amanita phalloides mushroom poisoning

Milk thistle has been used traditionally to treat Amanita phalloides mushroom poisoning. Not recommended.
Grade C

Key to grades

A Strong scientific evidence for this use
B Good scientific evidence for this use
C Unclear scientific evidence for this use
D Fair scientific evidence against this use

According to AHRQ, clinical efficacy of milk thistle is not clearly established. Interpretation of the evidence is hampered by poor study methods and/or poor quality of reporting in publications. Possible benefit has been shown for improvement in LFTs. Milk thistle is associated with few, and generally minor, adverse effects.

Synonyms for milk thistle

Bull thistle, cardo blanco, Cardui mariae fructus, Cardui mariae herba, emetic root, flavonolignans, heal thistle, holy thistle, isosilibinin, isosilybin, lady's thistle, Marian thistle, mariana mariana, Mary thistle, mild thistle, milk ipecac, pig leaves, royal thistle, silybin, silybinin, Silybum marianum, snake milk, St. Mary's thistle, thisylin, wild artichoke.

Does milk thistle affect the respiratory status of patients with asthma?

Pubmed search does not show any studies which have formally evaluated the effect of milk thistle on the respiratory system of patients with asthma or COPD but a significant effect appears unlikely.

Milk thistle (Silybum marianum). Mayo Clinic.
Milk Thistle: Effects on Liver Disease and Cirrhosis and Clinical Adverse Effects. AHRQ.
Milk thistle. University of Maryland.
Milk thistle, from Wikipedia, the free encyclopedia.
Image source: Wikipedia, GNU Free Documentation License.

Milk Thistle: Benefits and Side Effects. WebMD.


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