Milk Thistle: A Medicinal Plant to Grow for Its Benefits

Introduction to Milk Thistle

There are thistles and then there are thistles! Beneath their prickly appearance, from leaves to inflorescences, the term ‘thistle’ actually refers to several herbaceous plants belonging to different genera, most of which are part of the vast Asteraceae family. These include true thistles (Carduus), ornamental thistles (Echinops), plume thistles (Cirsium), carline thistles (Carlina), as well as sea hollies (Eryngium) and teasels. Among these spiky plants, milk thistle (Silybum marianum) holds a special place. It is, in fact, the sole representative of the Silybum genus! Yet on its own, it boasts numerous assets, both aesthetic and medicinal.

To benefit from milk thistle’s virtues, one must first get to know it well.

A Herbaceous Plant from the Asteraceae Family

Native to Mediterranean regions and parts of Asia, milk thistle is a rather robust herbaceous plant, thanks to its thick, spherical, and branched root. As a biennial plant, it produces a rosette of oval, leathery leaves in its first year, with irregularly toothed and spiny edges, glossy green in colour and marbled with white along the veins. In its second year, milk thistle develops an upright stem, leafy at the base and woolly on the upper part. In summer, between June-July and August-September, solitary flower heads bloom at the top of the stems. The purple flowers, surrounded by toothed and spiny bracts, produce brown, speckled fruits in the form of achenes, topped with a white, shiny pappus.

While milk thistle is often found growing wild on roadsides, wastelands, fallow land, and rocky slopes, it can also be sown and cultivated in a rural or urban garden. There, it can reach a height of 1.50 to 2 metres.

Sowing and Growing Milk Thistle

Milk thistle is typically obtained as seeds for sowing. Sowing takes place in February under cover or in April directly in the ground. February sowings will need to be pricked out into pots in March before being transplanted to their final position in April. For direct sowing, seeds are planted in rows spaced 50 to 60 cm apart, with seedlings later thinned to 60 cm intervals.

Thanks to its origins, milk thistle adapts well to dry, chalky, and poor soils, though it thrives best in rich soil. The key is ensuring the soil is perfectly drained, possibly lightened with sand. It also requires full sun.

How to use milk thistle?

While all tender parts of the milk thistle (young leaves and stems, flower heads, roots) are edible, it’s the leaves and achenes that are used in herbal medicine, as they contain the active compounds. These fruits are said to be particularly rich in flavonoids, especially silymarin, which is believed to have liver-protective effects. This medicinal property is officially recognised by the WHO (World Health Organisation).

How to harvest milk thistle?

The leaves are harvested during the flowering period of milk thistle, which occurs between June and September, depending on the region. These are the small rosettes of leaves that develop on the flowering stems, to be picked young before they become tough and spiny. They should then be dried in a dark, well-ventilated room, protected from any moisture. If you don’t have a suitable place, you can dry the leaves in an oven at 50°C with the door slightly ajar.

The seeds are collected from the faded flower heads, which have turned dry and brown. Often, the seeds naturally detach from the pappus that tops the achenes. Simply cut the dry flower heads and place them on an old sheet or in a large bag to continue drying for a month. The white bristles are clearly visible and can be allergenic. Wearing gloves, remove these bristles to collect the seeds. A hairdryer can be used to help remove the pappus.

Dried milk thistle flowers

How to use milk thistle seeds and leaves?

• Dried leaves are consumed as an infusion—use one teaspoon per 250 ml of boiling water. Steep for 10 minutes, strain, and drink. Three cups per day, half an hour before meals.
• Whole seeds are prepared as a decoction—use one teaspoon in 150 ml of cold water. Boil for 5 minutes, strain, and drink. Three cups per day, 30 minutes before meals.
• Seeds can be ground into a powder and consumed as an infusion. Use two teaspoons of powder per day.

It is recommended not to consume milk thistle continuously for long periods. A 3 to 6-week course is generally advised, followed by a break of a few weeks before resuming if necessary. This pause prevents the body from becoming accustomed to the active compounds and maintains the plant’s effectiveness.

What are the benefits of milk thistle for the body?

Consumed since antiquity by the Greeks, Romans, and in Ayurvedic medicine, milk thistle has a reputation as an essential plant for supporting liver protection. It benefits from traditional use in treating liver diseases. However, the benefits of milk thistle are not limited to this area alone.

The liver-protective action

Silymarin, the major active compound believed to be found in milk thistle, is thought to act on liver cells. It may play a role in liver regeneration and detoxification, as well as repairing liver cells by eliminating toxins—particularly after excessive alcohol or medication consumption, or liver poisoning. These flavonoids may also contribute to the production of new liver cells.

Milk thistle is logically considered a key ally in treating liver diseases, such as hepatitis, cirrhosis, or liver conditions related to gallstones…

The WHO officially recognises its liver-protective benefits in chemotherapy protocols for cancer to reduce side effects.

Milk thistle seeds are believed to contain silymarin, the major active compound

Digestive support

Milk thistle is also reputed to help improve digestion and promote healthy intestinal transit. Indeed, milk thistle is thought to stimulate bile production by the liver. By increasing bile secretion, the digestion of fats and absorption of fat-soluble nutrients become more efficient. Milk thistle may therefore have a cholagogic effect, much like artichoke leaf tea.

Milk thistle is also known to help relieve digestive discomfort in cases of irregular transit, indigestion, or digestive inflammation. It is also a natural support for gut microbiota.

Antioxidant and anti-inflammatory properties

When the body accumulates too many free radicals—generated by pollution, an unbalanced diet, smoking, etc.—it enters a state of oxidative stress. Thanks to its richness in antioxidants, milk thistle may help neutralise free radicals and support the immune system.

Still due to silymarin, milk thistle is believed to have anti-inflammatory properties, combined with its antioxidant effects, which may provide benefits in protecting against chronic diseases such as cardiovascular conditions, diabetes, or neurodegenerative disorders.

What are the side effects and contraindications of milk thistle?

Although milk thistle is generally well tolerated, some precautions should be taken into account.

Possible side effects

Minor digestive issues may occur, such as bloating, mild diarrhoea, or nausea. These effects are usually temporary and disappear after a few days.

Contraindications

• People allergic to Asteraceae.
• Pregnant or breastfeeding women.
• Individuals with hormone-dependent cancer.
• Interaction with certain treatments (anticoagulants, antidiabetics, hepatotoxic drugs).

In these cases, it is strongly advised to consult a healthcare professional for medical advice before consuming milk thistle.

Did you know?

Also known as silver thistle, holy thistle, Our Lady’s thistle, or milk thistle, the name ‘Mary thistle’ is said to come from a legend: while fleeing hastily from Egypt to Palestine, the Virgin Mary sought to breastfeed the infant Jesus. Drops of milk supposedly fell onto a thistle bush where she was hiding. This legend also explains the distinctive white marbling that adorns the leaves of the milk thistle.