Milk thistle (Silybum marianum), native to the Mediterranean region and southwestern Europe, has been widely cultivated for centuries as a culinary, medicinal, or ornamental plant. It is now naturalized throughout much of the European continent and South America. In California and Australia, the plant has become a common weed.(1)
As a medicinal herb, this prickly member of the sunflower family (Compositae) has been associated with the liver for at least 2000 years. The Roman physician and naturalist Pliny the Elder (a.d. 23–79) wrote about its use as a vegetable and mentioned that the juice, mixed with honey, was excellent for carrying off bile.(2) This is the first known reference to the use of milk thistle for liver disorders.
In her herbal Physica (circa 1150), Hildegard of Bingen (see June/July 1995 issue) wrote that milk thistle, which she called “Venus thistle”, was an effective treatment for tumors and the streptococcal disease erysipelas.(3)
At the time that Gerard’s Herball was first published, in 1597, milk thistle was being grown in English gardens and had become a weed in the countryside. Gerard extolled it as the best remedy against “melancholy” (liver-related) diseases.(4)
Milk Thistle: The Plant
Milk thistle’s generic name, Silybum, comes from the first-century Greek physician, Dioscorides, who applied the name to several other edible thistles as well. Its species name, marianum, means “of (the Virgin) Mary”. In Germany, where the plant is often depicted as a religious symbol associated with the Virgin Mary, the characteristic white mottling of the leaf veins is said to represent Mary’s milk.(5)
The stout, branching annual or biennial grows from 3 to 7 feet tall. The alternate, white-mottled, smooth, shiny, scalloped leaves serve as a tender and palatable salad herb when young, but they soon develop stiff spines on the margins. Solitary purple flower heads, up to 21/2 inches in diameter, appear in early summer above outward-spreading, spiny bracts. In nineteenth-century Europe, the roots were baked in vegetable pies; the young flower stalks were peeled, soaked in water to remove the bitter milky latex, then cooked and eaten like asparagus; and the fleshy unopened flower receptacles were boiled and eaten like artichokes.(6)
Each shiny black seed is crowned with a spreading, silky pappus similar to that of a dandelion seed. A favorite food of goldfinches, the seeds when roasted have been used as a coffee substitute. The seeds are the part of the plant that is of medical interest.
Historical and Modern Uses
The eighteenth-century German physician J. G. Rademacher advocated the use of milk thistle for chronic liver diseases and jaundice. In 1929, the German scientist H. Schultz investigated milk thistle while studying the value of historical herbal remedies and found a number of references to its use for liver ailments. Milk thistle seed preparations began to be available in German pharmacies in the 1930s, and there was a burgeoning interest in its clinical use.(7)
Few plant principles have been as extensively researched in recent years as has silymarin, a complex of compounds discovered in the seeds of milk thistle in the 1960s by Hildebert Wagner, a leading medicinal plant researcher (8). Later studies showed silymarin to be a complex of chemicals known as flavanolignans. Among those found in milk thistle seed are silybin, silydianin, and silychristin.(9) Numerous experimental studies during the past thirty years have demonstrated the pharmacological efficacy and safety of silymarin in laboratory models and have provided a scientific basis for the use of milk thistle in the treatment of liver disease.
Silymarin appears to help stabilize liver cell membranes and stimulates protein synthesis while accelerating cell regeneration in liver tissue that is damaged by alcohol and mood-altering drugs and chronic liver disease.(10) Preparations of silymarin (standardized to 70 to 80 percent silymarin) are currently used in European phytomedicine for the treatment of liver disease, including alcohol-induced cirrhosis, and amanita (death cup) mushroom poisoning.(11)
German health authorities equivalent to the U.S. Food and Drug Administration have established a panel known as Commission E to develop acceptable uses, contraindications, and dosages for well-defined herbal medicines in Germany. The commission’s monographs are the basis for regulation of herbal products in Germany and also serve as the model for European Union harmonization of laws on phytomedicines. Its milk thistle monograph permits the use of seed preparations for the supportive treatment of chronic hepatitis, cirrhosis, and fatty infiltration of the liver by alcohol and other chemicals, and notes that silymarin can also inhibit alcohol-induced liver damage, supporting its use as a preventive.(12)
(1) Foster, S. Herbal Renaissance: Growing, Using and Understanding Herbs in the Modern World. Layton, Utah: Gibbs Smith Publisher, 1993.
(2) Jones, W.H.S. Pliny Natural History with an English Translation in Ten Volumes, 7. Cambridge: Harvard University Press, 1966.
(3) Hahn, G., and A. Mayer. Der Deutsche Apotheker 1988, 40:6–7.
(4) Grieve, M. A Modern Herbal, 2. New York: Harcourt, Brace, 1931.
(5) ———. A Modern Herbal.
(6) Foster, S. Milk Thistle. Austin, Texas: American Botanical Council, 1991. Also Foster, Herbal Renaissance.
(7) Grieve, A Modern Herbal.
(8) Weiss, R. F. Herbal Medicine (translated from German by A. R. Meuss). Beaconsfield, England: Beaconsfield Publishers, 1988.
(9) Wagner, H., and O. Seligmann. In Chang, H. M., et al. (eds.). Advances in Chinese Medicinal Materials Research. Singapore: World Scientific, 1985.
(10) Hikino, H., and Y. Kiso. In Wagner, H., et al. (eds.). Economic and Medicinal Plant Research, 2. San Diego: Academic Press, 1988.
(11) Leng-Peschlow, E., and A. Strenge-Hesse. Phytotherapie 1991, 12(5): 162–174.
(12) Monograph Cardui Mariae Fructus, Bundesanzeiger No. 50, 1986.