From The October 1999 Issue of Nutrition Science News
By Lise N. Alschuler, N.D.
In an increasingly toxic world, we place growing burdens on the
body's detoxification system, the hub of which is the liver.
Millions of compounds are detoxified within each liver cell, or
hepatocyte. Inevitably, this wear and tear compromises liver
cells and surrounding connective tissue. Hepatotoxicity is fast
becoming a major health issue. In fact, many practitioners
believe poor liver function caused by toxin accumulation or by
liver-function decline may contribute to other seemingly
unrelated illnesses, such as rheumatoid arthritis, eczema,
migraine headaches and premenstrual syndrome, and may manifest
symptoms of its own. As a result, milk thistle (Silybum marianum)
is widely prescribed by herbalists throughout Europe and the
Americas for liver protection.
Milk thistle, also known as St. Mary's thistle and lady's
thistle, is native to Asia Minor, North Africa, southern Europe
and southern Russia. It has been naturalized to central Europe,
North and South America, and South Australia. The herb has
dark-green prickly leaves mottled or streaked with white veins,
blooms from June to September and can grow to six feet tall. Its
medicinal properties are found in the small, hard fruits,
sometimes called seeds but known technically as achenes, that
appear after the plant flowers.
Milk thistle fruits contain a mixture of flavonolignans--a unique
group of carbohydrates that share a common chemical structure.
These flavonolignans, the plant's active constituents, are known
collectively as silymarin. Silymarin usually comprises about 1.5
to 3 percent of the fruit and contains silybinin, the major
constituent, along with isosilybin, dihydrosilybin, silydianin,
silychristin, and probably a few flavonoids. The fruits also
contain 20 to 30 percent fixed oil (a combination of fatty acids
that are solid at room temperature), mucilage, protein and
taxifolin (a chemical with unknown significance).
Although milk thistle's mechanism of action has not been fully
explained, the herb has a long history of use as a liver
protectant and liver decongestant. (A liver decongestant
stimulates bile flow through the liver and gallbladder, thus
reducing stagnation and preventing gallstone formation and
bile-induced liver damage.) Pharmacological investigations have
centered on silymarin, which is most notable for its
antihepatotoxic activity. This effect has been demonstrated
against a variety of potent liver toxins including those from the
death cap mushroom (Amanita phalloides). [1, 2] S.
marianum extract works as both a preventive and antidote for
death cap mushroom poisoning. Intravenous administration up to 48
hours after ingestion is effective. 
Finnish researchers conducted a double-blind, controlled study to
look at the effect of milk thistle fruit extract on liver
inflammation. They measured levels of serum transaminase, an
enzyme released from inflamed liver cells, in 97 patients. All
subjects reportedly abstained from alcohol during the four-week
study during which they received either a 420 mg daily dose of
standardized S. marianum extract (Legalon, manufactured by Madaus
AG of Germany) or placebo. Subjects who received the extract
showed a statistically significant decrease in liver enzymes
compared with those taking placebo. 
In a larger clinical trial, researchers assessed the benefits of
milk thistle extract on 170 patients, 91 of them alcoholics with
liver cirrhosis. Subjects received 140 mg silymarin three times
daily for 41 months. The four-year survival rate was 58 percent
in the silymarin group and 39 percent in the placebo group--a
difference of 19 percent. The reduced death rate among those
taking silymarin was most pronounced in the alcoholic cirrhosis
subgroup. There were no side effects from silymarin. 
This study is significant for several reasons. The results
support the idea that long-term treatment with milk thistle
extract is beneficial and not likely to be harmful. These results
also suggest milk thistle extract may be particularly effective
for patients with alcohol-induced liver damage.
In all, studies suggest S. marianum protects the liver. It is
prescribed for any condition of threatened or obvious
hepatotoxicity including chronic daily exposure to environmental
pollutants, toxic effects of viral hepatitis, toxic side effects
of certain medications, toxicity from chronic alcohol use,
cirrhosis and fatty degeneration of the liver. Milk thistle
extract should help improve liver function, protect hepatocytes
and increase bile flow for anyone with these
conditions.  The antihepatotoxic effects are quite
pronounced while the liver-decongesting and bile-stimulating
effects are mild and gentle. This herb is extremely well
Milk thistle is effective in a variety of preparations, though
the traditional one is a medicinal tea or decoction. Silymarin is
poorly soluble in water but historical use indicates its
bioavailability increases if the crushed fruits are soaked
overnight before being boiled for 15 minutes. A therapeutic tea
contains 1 to 3 tablespoons of crushed fruits per 8 to 10 ounces
of water. Another preparation is alcohol and water extraction,
commonly known as a tincture. Encapsulated standardized milk
thistle extract is the preparation studied in clinical trials.
Extracts are typically standardized to 70 percent of the
silymarin complex. The typical dose is 200 to 420 mg daily taken
in three divided doses with meals for eight weeks, then 280
mg/day in three divided doses. There are no known side effects or
contraindications, and this herb is safe for use during pregnancy
Milk thistle can be taken as a preventive measure, particularly
if a person eats chemically processed foods, is exposed regularly
to foreign compounds that require detoxification, has a known
liver disease or family history of liver disease, or drinks
alcohol regularly. Long-term continued use has no known side
effects or contraindications. Recommend that customers
discontinue use for two to seven days every eight weeks to
maintain effectiveness, as they should with any herbal medicine.
Pollutants, toxic medications and exposure to infectious
organisms underscore the need for liver protection. Milk thistle
offers a reliable and safe solution.
Lise N. Alschuler, N.D., received her degree from Bastyr
University, Bothell, Wash., where she is currently the clinical
medical director. She also has a private practice in Seattle.
Commission E Monograph
Milk Thistle fruit
Name of drug: Cardui mariae fructus, milk thistle fruit
Composition of drug: Milk thistle fruit consists of ripe
seed of Silybum marianum (L.) Gaertner [Fam.
Asteraceae], freed from the pappus, and its preparations
in effective dosage. The drug contains silibinin, silydianin and
Uses: Crude drug--dyspeptic [digestive] complaints.
Formulations*--toxic liver damage; for supportive treatment in
chronic inflammatory liver disease and hepatic cirrhosis.
Contraindications: none known
Side effects: Crude drug--none known; Formulations--a mild
laxative effect has been observed in occasional instances.
Interactions with other drugs: none known
Dosage: Unless otherwise prescribed, average daily dose of
drug is 12 to 15 g; formulations equivalent to 200 to 400 mg of
silymarin, calculated as silibinin.
Mode of administration: Powdered drug for making infusions
and other galenical formulations to be taken by mouth.
Actions: Silymarin acts as an antagonist in many
experimental liver-damage models: phalloidin and -amanitin
(death-cap toxins), lanthanides, carbon tetrachloride,
galactosamine, thioacetamide, and the hepatotoxic virus FV3 of
The therapeutic activity of silymarin is based on two sites or
mechanisms of action: a) it alters the structure of the outer
cell membrane of the hepatocytes in such a way as to prevent
penetration of the liver toxin into the interior of the cell; b)
it stimulates the action of nucleolar polymerase A, resulting in
an increase in ribosomal protein synthesis, and thus stimulates
the regenerative ability of the liver and the formation of new
*Note: "Formulation" refers to an extract standardized to at
least 70 percent silymarin, the collective name for the three
compounds listed in the "Composition of drug" section above.
Reprinted with permission from The Complete German
Commission E Monographs--Therapeutic Guide to Herbal
Medicines, a 700-page guide featuring 380 monographs. The
guide is published by the American Botanical Council, Austin,
Faulstich H, et al.
Silybin inhibition of amatoxin uptake in the perfused rat liver.
Arzneim-Forsch Drug Res 1980; 30: 452-4
Tuchwever B, et al.
Prevention of silybin of phalloidin induced acute hepatoxicity.
Toxicol Appl Pharmacol 1979; 51: 265-75
Hruby K, et al.
Effect of the flavolignans of Silybum marianum L. on lipid peroxidation in rat liver microsomes and freshly isolated hepatocytes.
Pharmacol Res 1992; 25: 147-54
Salmi H, Sarna S.
Effect of silymarin on chemical, functional, and morphological alterations of the liver.
Scand J Gastroenterol 1982; 17: 517-21
Ferenci P, et al.
Randomized, controlled trial of silymarin treatment in patients with cirrhosis of the liver.
J Hepatol 1989; 9: 105-13
Nassauto G, et al.
Effect of silibinin on biliary lipid composition: experimental and clinical study.
J Hepatol 1991; 12: 290-5
Return to the MILK THISTLE Page