Description
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Milk thistle, or Silybum marianum, is a biennial thistle-like plant, up to 1.5 m in height, with large, spiny, lobed
leaves. The leaves are specked with white, especially along the nerves. The flower heads are reddish violet,
with bracts ending in a recurved thorn. The seeds, fruit, and leaves are all used for medicinal purposes, but the
fruits contain the highest amounts of chemical and nutrient value. It has been utilized for its therapeutic
characteristics for over 2,000 years.
Composition
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Milk thistle contains silymarin, which was first isolated from milk thistle seeds in 1968. Silymarin consists of
three major flavolignans: silybin, silychristin, and silidianin, of which silybin is the most biologically active.
Although the concentration of silymarin is highest in the fruit, it is also found in the seeds and leaves. Milk thistle
also contains other active phytochemicals, which include:
Glucosides
Glucose attached to non-sugar molecules, such as flavonoids. These molecules are integral to the
pharmacological activity of milk thistle. The three major flavonoids present are: apigenin, kaempferol, and
Polyacetylenes
Phytochemicals derived from the roots of the plant.
Fumaric acid
Fumaric acid is an unsaturated dibasic acid, C4H4O4, which is the trans-isomer of maleic acid and an
intermediate in the Kreb’s cycle.
Flavolignans
Dehydrosilybin, 3-deoxysilichristin, deoxysilydianin (silymonin), siliandrin, silybinome, silyhermin and
Silybonol
A plant oil found in the seeds, consisting of linoleic, oleic, myristic, palmitic and stearic fatty acids, along with
betaine hydrochloride and triamine.
Sitosterol
Dorland’s Medical Dictionary defines sitosterol as any group of closely related plant sterols, preparations of
which are used as anticholesterolemic agents.
Pharmacological Action
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Milk thistle protects liver cells and acts as an antioxidant. Silybin has a steroid structure that is able to
regenerate liver cells by stimulating DNA/RNA synthesis (Sonnenbichler J et al. Proceedings of the International
Bioflavonoid Symposium (Munich, Frg) 1981;477). Silybin can also raise the activity levels of the free
radical-scavenging enzymes superoxide dismutase and glutathione peroxidase (Altorjay I et al. Acta Physiol
Hung 1992;80:375-80). The ability to stabilize cell membranes may explain the inhibition of histamine release
from basophils (Miadonna A. et al. Br J Clin Pharmacol 1987;24:747-52). Silymarin can reduce formation of
leukotrienes by inhibiting the enzyme responsible for their formation (lipoxygenase) (Fiebrich F and Kock H.
Experientia1979;35:148-150).
Silymarin may exhibit some of its hepatoprotective characteristics by beneficially changing the outside cell
membrane structure (Foster S. Botanical Series No. 305, American Botanical Council, Austin, Tx. 1991;3-7).
Silymarin can block binding sites for toxins and prevent them from being taken up into the cells (Hobbs, C. Milk
thistle: The liver herb, 2nd edition, Botanica Press, Capitola, Ca. 1992;1-32). Silymarin scavenges free radicals,
and increases concentrations of the highly detoxifying glutathione (Valenzuela A et al. Biological Research
1994;27:105-12).
Clinical Applications/Research
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* Cirrhosis
* Hepatitis
* Jaundice
* Alcohol abuse
* Pesticide/pollution exposure
* Gallstone prevention
* Blood/circulation
* Immunomodulation
* Lipid/biliary disorders
* Drug-induced liver damage
* High cholesterol
* Atherosclerosis
* Lactation
* Diabetic complications
* Ulceration
* Liver, spleen and kidney congestion
* Psoriasis
* Varicose veins
* Menstrual difficulty
Milk thistle has its main action on kidney and liver. It has a reputation for being hepatoprotectant. Milk thistle has
been employed as a cholagogue (agent to stimulate gallbladder contraction and promote bile flow) in
supportive treatment of hepatic and biliary functional disorders. It has also been employed as an antimalarial,
emmenagogue agent promoting menstruation), and in disorders of the uterus and spleen (Grainger, NB ed.,
Herbal Drugs and Phytopharmaceuticals. Medpharm Scientific Publishers. CRC Press. Boca Raton, Fla.
1994). Milk thistle has been utilized to stimulate milk production in nursing mothers (Awang D. Can Pharm J
1993;403-404), as an antidepressant (ibid), for steroid secretory modulation (Racz K et al. J Endocrinol
1990;124:341-345), and as support for promyelocytic leukemia (Invernizzi R. et al. Haematologica
1993;78:340-341). Milk thistle components are known to stimulate protein synthesis, however they do not
stimulate malignant liver tissue (Sonnenbichler J et al. Biochem Pharm 1985;34:2209-2212).
Silymarin has proven in documented results that it protects liver cells against the toxic assault of amanita
poisoning, tetracycline, thallium, erythromicin, amitriptyline, nortriptyline, tert-butylhydroperoxide, phenothiazine
and butyrophenone (Hruby K. Intensivmed 1987;24:269-274; Skakun N et al. Antibiot Meditsin Biotekh;
Tyutyulkova N et al. Methods Find Exp Clin Pharmacol 1981;3:71; Mourelle M et al. J Appl Toxicol
1988;8:351-354; Davila J et al. Toxicology 1989;57:267-286). It also protects against carbon
tetrachloride-induced liver cirrhosis (Letteron P et al. Biochem Pharmacol 1990;39:2027-2034). Silymarin was
even known to demostrate a protective effect against the epithelial cells of the liver after exposure to a lethal
hepatotoxic virus by inhibiting the release and/or synthesis of hepatotoxic enzymes (Condrault JL et al. Planta
Medica 1980;39:247).
Silymarin has an antiinflammatory effect on blood platelets (Altorjay I et al. Acta Physiol Hung 1992;80:375-80),
and thus may be helpful in blood disorders and immunomodulation. Silymarin lowered total cholesterol levels
in a clinical trial conducted on type II hyperlipidemic patients (Somogyi A et al. Acta Med Hung 1989;46:289-295).
In a double-blind controlled study involving 50 patients with alcoholic cirrhosis, silymarin normalized existing
elevated levels
of liver enzymes (AST and ALT), serum bilirubin, and gamma-glutamyl transferase
(Lang I et al.
Ital J
Gastroenterol 1990;22:283-287). Postitive results were also seen in acute viral
hepatitis, with the same
normalization of bilirubin and liver enzymes exhibited, and treatment time shortened in the
silymarin-supplemented group (Magliulo E. et al. Med Klin 1978;73:1060-1065), and also in chronic hepatitis
(Kriesewetter E et al. Leber Magen Darm 1977;7:318-323).
The ability of silymarin to inhibit leukotriene synthesis and to improve liver function are believed to contribute to
its therapeutic effect in psoriasis. The liver filters toxins out of the blood, and psoriasis has been highly
correlated to high levels of circulating endotoxins, for example, the ones found in the cell walls of gut bacteria.
Thus, the liver’s function is an important consideration is psoriasis, and if liver function is impaired, or if the liver
is overwhelmed with endotoxins, environmental toxins, NSAIDS etc., it may aggravate the psoriasis. Also,
excessive leukotriene synthesis is correlated to psoriasis, and silymarin can reduce formation of this
inflammatory eicosanoid by inhibiting the enzyme responsible for its formation (lipoxygenase) (Fiebrich F and
Kock H. Experientia1979;35:148-150).
Silymarin is a lipophilic (lipid-phase) antioxidant, which, when tested against hydrophilic antioxidants, "produced
significant protection" from the toxic, immunosuppressive compounds that block the bile acid uptake system of
hepatocytes (J Endocrinol. 1990;124(2):341-5). Silymarin is a, "known hepatoprotective agent", which brings the
glutathione (GSH) level back to normal after depletion (Biochem Pharmacol. 1993;46(1):182-5). Silymarin not
only prevents the depletion of GSH, it even increased the basal level of this detoxifying enzyme by 35% in one
study (as cited by Murray, M.T., N.D. and Pizzorno, J.E., N.D. Enc. of Natural Medicine. 1991. Prima Publishing,
Rocklin, Ca., p.82).
Silymarin and its main flavolignan, silybin, have both been clinically evaluated in diabetics for their therapeutic
value in reducing diabetic complications (Zhang J et al. Chung-Kuo Chung His I Chieh Ho Tsa Chih
1993;13:725-26), in treating aged skin (Khafagy S et al. Scientia Pharmaceutical 1981;49:157-161), and in
inhibiting ulceration (rat study) by decreasing the neutrophils in the gastric mucosa, and by inhibiting
peroxidation and subsequent inflammatory leukotriene formation (Alarcon de la Lastra, C. et al. J Pharm
Pharmacol 1992;44:929-931; Alarcon de la Lastra, C. et al. Planta Medica 1995;61:116-119).
Suggested Dosage
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Recommendations for milk thistle are based on its content of silymarin (from 70-210mg, 3 times a day).
Contraindications/Toxicology
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Milk thistle has an excellent safety profile. A substantial amount of evidence points to the lack of toxicity from its
use (Awang D. Can Pharm J 1993;422:403-404). There are no reports of it being toxic in man (some toxicity has
been observed in sheep and cattle). An isolated case of urticaria was reported in a foreign commercial milk
thistle preparation. Use of milk thistle is inadvisable in decompensated cirrhosis (Rumyantseva Z. Vrach Delo
1991;15-19).
Mild gastrointestinal/mild allergic reactions have been observed with silymarin used alone (extracted from milk
thistle), but side effects are considered rare. Mild laxative effects in isolated cases have been reported. No
toxicity was reported during pregnancy or the post-natal period in rats, and fertility was not affected (Legalon
booklet, Madaus AG, D-5000 Koln, West Germany 91, 1989;3-42). It has proven to be non-toxic in animal
studies where the mice received up to 5000 mg/kg (high dose) without showing any symptoms.
The statements above have not evaluated by the FDA. The nutritional suggestions and research provided are not intended to diagnose, treat, cure or prevent disease and should not be used as a substitute for sound medical advice. Please see your health care professional in all matters pertaining to your physical health. The Professional Notes, Patient Instructions, and items marked with an astrisk (*) are provided by the practitioner and are the sole responsibility of the practitioner.Copyright © 1998-2002 Standard in Natural Solutions, LLC.