Milk Thistle - Silybum marianum

Common Names: Milk thistle, Mary thistle, St. Mary thistle, Scotch thistle, Variegated thistle, Marian thistle, Legalon, Carduus marianus, Cardui Mariae Herba, Cardus marianus, Chardon Argenté, Artichaut Sauvage, Shui Fei Ji, Silymarin, Silymarine, Silibinin, Silybum marianum, Cardui Mariae, Global: Milk thistle, English: Milk thistle, Silybum marianum, Latin: Silybum marianum

Latin Name: Silybum marianum

Origin: Africa, Asia, Australia, Europe, South America, North America

Short Introduction

Harvesting milk thistle by hand can be quite challenging—even unpleasant or potentially hazardous—for some due to its thorny character. The seeds are typically collected in Europe once a year, from August to September, about 2–3 weeks after flowering. Before fully ripened, the entire flower heads are cut and placed in a dry, airy environment to allow for maturation. The seeds can then be easily threshed from the heads. Once dried, the seeds are odorless with a slightly bitter taste. In the Czech Republic, milk thistle is commonly cultivated in gardens, but it can also be found in waste grounds, fields, meadows, and rocky slopes.

Detailed Description

An ordinary thistle with extraordinary properties.

Botanical Information

Milk Thistle is an annual or biennial herb with a taproot and a sparsely branched, sturdy stem reaching up to 2 meters in height. At its base, the plant can spread up to 160 centimeters wide. The stem is rounded with white pith inside. Its leaves form a basal rosette up to 40 cm long; upper leaves are sessile, obovate to lanceolate, and pinnately lobed with finely spiny edges. The flower heads are single, large (3–7 cm), surrounded by unevenly spiny bracts. The flowers are reddish-purple, around 4 cm long, with a white corolla tube, appearing from June to August in the Northern Hemisphere and from December to February in the Southern Hemisphere. The fruit is a several-millimeter-long, flattened, shiny achene with a deciduous pappus. If grown as an annual, the plant sprouts a cluster of spiny leaves with white veins in spring, followed by purple-red flower clusters on the stems at the end of June. The seeds mature by late summer and are then harvested.

Origin and Distribution

Milk Thistle most likely originated in the Mediterranean, Asia Minor, and the Canary Islands. Some botanists place its native region in the mountainous areas of Crete and Greece, while others suggest the southeastern coast of England. Today, milk thistle grows far beyond its potential native areas—from North America, through Australia and New Zealand (where it is considered an invasive weed), to Iran and Central Asia. It was probably introduced secondarily to Central Europe, where it has since naturalized. The pharmaceutical industry now grows the plant extensively in Austria (especially Waldviertel), Germany, Hungary, Poland, China, Argentina, as well as in the Czech Republic.

Usage / Dosage

Milk thistle is sometimes grown in gardens as a decorative plant (with its imposing stature and striking appearance), and dried flower heads are popular in ornamental dry bouquets. It’s a classic thistle that is best given a respectful distance, but its dense growth makes it an effective natural barrier or “living fence.”

One of the most popular ways to consume milk thistle is to brew tea from crushed seeds. Crushing the seeds ensures sufficient release of active compounds, and soaking in cold water is recommended, as heat can degrade the beneficial substances. Some methods blend or add whole seeds to yogurt, foods, beverages, juices, and more.

The active compounds in milk thistle are most widely recognized for their role in preventing fatty liver (hepatic steatosis) and ameliorating various types of liver inflammation. A large body of evidence has led health organizations worldwide to endorse milk thistle for maintaining normal liver function with regular use. Scientific research describes the benefits of milk thistle seed components in the treatment and prevention of some forms of hepatitis.

Several studies demonstrate the potential of milk thistle compounds in supporting the treatment of liver diseases, prevention and treatment of cancer, and as an aid in poisoning from toxic mushrooms. A 2007 Cochrane review summarized the results of 18 clinical trials involving 1,088 patients with alcoholic hepatitis and/or hepatitis B, C, or viral-induced liver disease.

Some research reports highlight regular use of milk thistle compounds in managing certain cancer types (prostate, skin, breast, and cervical) and their positive effect on T-lymphocytes, resulting in an anti-inflammatory effect. In addition to boosting liver enzyme levels, milk thistle also appears to protect tissues, with the most studied and verified protection afforded to liver tissue.

Several of the compounds in milk thistle seed extract are recognized as powerful antioxidants. Their antioxidant properties are thought to be so significant as to bring anti-inflammatory benefits and support elements of the immune system.

One study recommends some compounds found in milk thistle seeds for supporting healthy digestion, promoting the liver’s natural detoxifying processes, and purifying the digestive tract and blood. Some authors recommend extracts or seed components after excessive alcohol consumption. Other sources note benefits during drug-induced liver injury, post-recovery, radiation therapy, chemotherapy, or after long-term antibiotic use.

Additionally, milk thistle compounds may help lower blood sugar levels, contribute to healthy heart function in certain conditions, and generally support cardiovascular health. The digestive tract appears to be cleansed by these components, and they may have a mild laxative effect. It’s also worth noting that some flavolignans show potential antiviral and anticancer effects.

Homeopathy

In homeopathy, Silybum marianum is used to improve gallbladder function, help with gallstones, and manage depressive states.

Traditional Herbal Medicine

In folk medicine, milk thistle is valued—based on long experience—for treating liver and bile duct ailments. Some extracts are also appreciated for their strong antioxidant, anti-inflammatory, and protective roles in liver health.

Active Compounds

The most important and biologically active compound in milk thistle is silymarin, found in seeds at about 4–6%. Silymarin is actually a complex mixture of polyphenolic molecules, primarily seven structurally related flavolignans (silydianin, isosilybin A and B, silybin A and B, silychristin, and isosilychristin) and one flavonoid (taxifolin). Sometimes, you’ll see silibinin mentioned in the literature—a partially purified silymarin fraction rich in silybin A and B in a 1:1 ratio. The achenes (seeds) contain up to 35% unsaturated fatty acids (linoleic, oleic, linolenic, and arachidonic acids) and smaller amounts of saturated fatty acids (stearic, palmitic, and caproic acids), as well as essential oils, mucilaginous substances, and proteins.

Traditional Dosage

The most effective use is to consume crushed seeds. Eating the seeds directly ensures optimal absorption and delivery of active compounds directly to the intestines, where they are needed. The most suitable form is freshly crushed seeds that have not come into contact with metal and have not been exposed to temperatures above 80°C. The typical dosage is 3–4 grams of seeds, taken 3–4 times daily on an empty stomach (about two hours after a meal or 30 minutes before eating). For tea, use a similar amount (around 4 grams), pour water at 80°C, steep for 15 minutes, and sip several times a day. Some methods suggest simmering a tablespoon of seeds for 15 minutes, then drinking after it cools. Crushed seeds can also be boiled for just 5 minutes; since active compounds are primarily under the seed coat, water can reach them easily in this form.