Milk thistle: we need this weed!

Better Nutrition, Oct, 1997 by Steven Foster

In June of 1997, I saw an excellent news report aired by ABC's 20/20 on St. John's wort's usefulness in treating mild to moderate depression. One of the physicians interviewed for the piece said that St. John's wort was the flagship of herbal medicine, and the best-researched herb in the world. I sat there in my chair and said to myself. "Wrong." With all due respect to St. John's wort, when I think of the best-researched herb in the world from the standpoint of known active constituents, proven pharmacological mechanisms of action, proven clinical effectiveness through dozens of controlled clinical studies and decades of experience, and an excellent safety record, there is only one herb that can fit all of those criteria. It is milk thistle.

Milk thistle preparations are from the seeds of Silybum marianum, a member of the sunflower family native to a narrow area of the Mediterranean, but grown for centuries throughout Europe and naturalized on that continent. It is also naturalized in the United States. In fact, it is a common weed in California. It was brought to America by early settlers, probably as a food plant, and became established in the eastern United States, as well as the West. By the turn of the century, it was already common in California, in abandoned fields, old pastures, and by roadsides. It is also naturalized in some areas of South America, and Australia, where it is a nuisance weed, and forms thickets.

Milk thistle has black shiny seeds, crowned with feathery tufts like those of dandelion seeds. It is the seeds that have been the subject of interest among herbalists.

Traditionally, seeds have been roasted for use as a coffee substitute, but it is their historical and modern use in the supportive treatment of liver disease that has attracted the most attention. Use of the plant as a liver-protecting agent dates back to at least the first century.

Milk thistle's long history

Dioscorides, a first-century Greek physician who served the Roman army, gave the name Silybum to a number of edible thistles. Now the genus name Silybum is given to two species originating from the Mediterranean region, including our subject Silybum marianum. The name milk thistle refers to the white streaks along the leaf veins. In Germany, where the plant is often depicted as a religious symbol associated with the Virgin Mary, legend ascribes the white mottling to a drop of the Virgin Mary's milk. The species name "marianum" honors the symbolic association of the plant with the Virgin Mary.

Modern use of milk thistle in medicine is limited to the seeds. The plant has gained prominence based on scientific research in the past 30 years. However, its use is not the result of new biological screening that catapulted it into prominence as a "new" medicinal plant. Rather, its use as a liver-protecting herb dates back to the earliest Greek references to the plant.

Pliny the Elder (A.D. 23-79), the first-century Roman physician/naturalist wrote about use of the plant as a vegetable, but warned it was not worth the effort to boil it, as it was troublesome to cook. He also mentioned that the juice of the plant, mixed with honey, is excellent for "carrying off bile." This is perhaps the first reference to the use of milk thistle for liver-related conditions.

A thousand years later, the plant was already well known in Germany. It is mentioned in an important medieval German manuscript, the Physica of Hildegarde of Bingen, the first herbal written by a woman, composed about 1150 and first published in 1533. Hildegarde -- a theologian, music composer, and writer -- was herself a "renaissance women," before the age of the Renaissance. She wrote about the uses of the roots, whole plant, and leaves of milk thistle, which she called "vehedistel" or Venus Thistle.

Still used in the 18th century, Culpepper (1787 ed.) noted that it can be used "to open the obstructions of the liver and spleen, and thereby is good against the jaundice."

Milk thistle in the 20th century

Reinvestigating the value of traditional herbal remedies, in 1929, H. Schultz, a German scientist, began to look into the value of milk thistle. He found that a famous 18th-century German physician, Rademacher, had advocated the use of milk thistle preparations for chronic liver diseases, acute hepatitis, and jaundice. By the 1930s, once again, clinical interest in milk thistle was beginning to emerge.

Intensive research into the liver-protecting (hepatoprotectant) properties of the plant, the responsible chemical components, and mechanisms of action, began about 30 years ago. Attempts to isolate the active components of the seed were begun in 1958. Ten years later, a research team headed by H. Wagner at the University of Munich was successful in isolating a compound termed silymarin which was believed to be a single compound. Improved chemical separation methods later revealed that silymarin was not a single component, but a complex of chemicals known as flavonolignans.

The primary components isolated and structurally characterized from silymarin include silybinin, silydianin, and silychristin. Collectively, these isoflavonolignans are found in concentrations of 4 to 6 percent in the ripe seeds.