Milk Thistle

Silybum marianum Asteraceae.  The common name is milk thistle.

Silybum is a member of the family Asteraceae and is closely related to other thistles.  It is large plant, growing from four to ten feet tall with sharp prickly leaves covered with white markings.  The purple flowering heads are typically thistle and quite large with many sharp spines.  Although originating in Europe, silybum has spread across the world and is a common weed in the United States, Africa, India, China, Australia and South America.

Silybum has been used as a medicinal plant for over 2,000 years.   The plant appears to have originated in southern to central Europe.   Its use as a liver protecting agent dates back to early Greek references, Dioscorides recommending it for snakebites.  The Roman, Pliny the Elder (A.D.23-79) refers to it as carrying off bile.  The English Gerard recommends it for melancholy associated with diseases of the liver and bile.  The American Eclectics, a school of medical herbalists of the late 19^th the early 20^th century, mention it for congestion of the liver, spleen and kidneys, menstrual difficulties and varicose veins.  Serious research into the hepatoprotectant effect of silybum began about twenty years ago, with interest shown particularly in Germany.

There can be some confusion as to nomenclature.  It has had several name changes and can be found in older texts as Carduus marianus L., and Cnicus marianus.  The specific name marianus represents

the myth that a drop of the Virgin Mary’s milk caused the white mottling of the leaves.  It has also had traditional use as a galactogogue, which contributes to the common name of Milk Thistle, and older common names, such as Mary Thistle, St. Mary Thistle and Lady Thistle.  The plant was long cultivated in European gardens as a vegetable.

The whole seed is used for the medicinal qualities.  The entire plant is edible:  leaves, roots, flower head and seeds.  The seeds are available as a bulk herb but are usually processed and are available as a hydroalcoholic extract, glycerite and standardized extract of 80-70% silymarin.  Capsules and standardized pills are common on the market.

Silybum is considered a hepatoprotective liver regenerator.  The primary active ingredients consist of a group of flavonolignans: silydianin, silychristin and silybin, which are collectively called silymarin.   It is concluded that silymarin, in addition to being a strong antioxidant, alters the liver cells outer membranes to prevent the uptake of toxins, enhances the regeneration of liver cells by increased protein synthesis and increases glutathione levels.  Silymarin concentrates in the liver, and because of enterohepatic circulation, repeatedly recycles itself through the liver.

The best known studies are connected with Amanita phalloides poisoning.  Silymarin helps both animal and human livers to combat the damage caused by the hepatotoxic principle phalloidin and alpha-amanitin.  Silymarin counteracts the attack by blocking membrane binding sites and by helping to promote regeneration of liver cells.¹ The results are dependent  upon the time interval of ingestion and treatment and the amount of liver damage.  The form of silymarin used in the studies and in treatment in Europe is an

intravenous infusion.  It is doubtful that oral ingestion would be as effective.²

Silybum is strongly antioxidant, and most data points to the silymarin as responsible for these effects.   Silymarin increase glutathione levels in the liver, intestine and stomach.³ The indications are that it is helpful in the protection of the liver against industrial toxins,⁴  food toxins such as aflatoxins, alcohol and chemical drugs.  It has been found to protect the liver from acetaminophen toxicity.⁵   The best results are obtained when silybum is ingested before exposure.

These antioxidant properties that are capable of scavenging both free radicals and reactive oxygen species, are currently under investigation for other uses than liver damage and protection.  There is recent evidence that silymarin can offer protection against solar-caused nonmelanoma skin cancers.⁶

The studies done with acute viral hepatitis suggest that treatment with silymarin “decreases complications, hastens recovery and shortens hospital stays.”⁷  The studies with all kinds of hepatitis have been  favorable, the studies themselves, however, tend to be difficult to interpret or have flaws.  There is a significantly reduced mortality rate in alcohol induced liver cirrhosis when treated with silymarin.  Silybum has been shown to help prevent liver damage from hepatotoxins including butyrophenones, phenothiazines, acetaminophen, halothane, dilantin and ethanol.⁸

Clinical uses of silybum range from toxic liver damage to the supportive treatment of hepatitis, and fatty infiltration of the liver by alcohol and other chemicals.  It is also considered useful for subclinical liver disease that some consider common in our culture.  It is also used prophylactically to protect the liver from exposure to toxins including alcohol, pharmaceutical drugs, x-rays and industrial toxins.

The constituents thought to be the primary active group are flavonolignans that are called collectively silymarin and consist of silybin, silydianin and silychristin.  Other chemicals that have been isolated are apigenin, silybonol, mytistic, palmitic, stearic and oleic acids.  Indian researchers have recently found that the seeds are also high in betaine hydrochloride, and are suggesting that this could also contribute to the antihepatotoxic effects.⁹

The German  Commission E recommends 200-400 mg. silymarin as a medium daily dose.  This is calculated with a standardized product of 70 to 80% silymarin.  A hydroalcoholic extract should be 95% alcohol for a complete extraction.  The recommended dosage is from 5 to 60 drops three times a day.  Herbalists recommend that a course of treatment should last from one to three months before judging if it is to be an effective remedy.

Silybum is consider safe with no reported side effects other than occasionally loose stools.  Clinical herbalist report occasional liver symptoms such as irritability, headache or mild GI upset, especially in the first few days of taking it