The Healing Power of Herbs
Excerpt
The following information is from the book; The Healing Power
of Herbs, by Michael T. Murray, N.D. The book was updated
in 1995 and is published by Prima. Dr. Murray is also the
co-author of Encyclopedia of Natural Medicine.
Milk Thistle
Key
uses of Milk Thistle:
General description
Milk thistle (Silybum marianum) is a stout, annual or biennial
plant, found in dry rocky soils in southern and western Europe
and some parts of the United States. The branched stem grows
1 to 3 feet high and bears alternate, dark green, shiny leaves
with spiny, scalloped edges that are markedly streaked with
white along the veins. The solitary flower heads are reddish-purple
with bracts ending in sharp spines. Flowering season is from
June to August. The seeds, fruit, and leaves are used for
medicinal purposes.1
Milk thistle has also been referred to as Mary thistle, Marian
thistle, Lady's thistle, Holy thistle, and the wild artichoke.
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Chemical composition
Milk thistle contains silymarin, a mixture of flavonolignans
consisting chiefly of silybin, silidianin, and silichristine.1-5
The concentration of silymarin is highest in the fruit, but
it is also found in the seeds and leaves. silybin is the silymarin
component that yields the greatest degree of biological activity.
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History and folk use
Perhaps the most widespread folk use of this plant has been
in assisting the nursing mother in the production of milk.
It was also used in Germany for curing jaundice and biliary
derangements. It is interesting to note that the discovery
of the liver-protecting compound silymarin in Milk Thistle
was not the result of extensive pharmacological screening,
but rather of investigation of silybum's empirical effects
in liver disorders.1
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Pharmacology
Milk thistle extracts (usually standardized to contain 70
to 80 percent silymarin) are currently widely used in European
pharmaceutical preparations for hepatic disorders. Silymarin
is one of the most potent liver-protecting substances known.1-9
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Actions relating to the liver
Milk thistle's ability to prevent liver destruction and enhance
liver function is due largely to silymarin's inhibition of
the factors that are responsible for liver damage, coupled
with its ability to stimulate the growth of new liver cells
to replace old damaged cells.
One of the ways the liver can be damaged is a result of certain
toxins producing or acting as free radicals. Free radicals
are highly reactive molecules that can damage other molecules,
including those in cells. Silymarin prevents free radical
damage by acting as an antioxidant. Silymarin is at least
ten times more potent in antioxidant activity than vitamin
E .1-4
Silymarin also increases the glutathione (GSH) content of
the liver by over 35 percent in healthy subjects and by over
50 percent in rats, and increases considerably the level of
the important antioxidant enzyme superoxide dismutase in cell
cultures.10,11
Glutathione is responsible for detoxifying a wide range of
hormones, drugs, and chemicals. Increasing the glutathione
content of the liver means the liver has an increased capacity
for detoxification reactions.
Another way in which the liver can be damaged is by the action
of leukotrienes. These compounds are produced by the transfer
of an oxygen molecule to polyunsaturated fatty acids, a reaction
catalyzed by the enzyme lipoxygenase. Silymarin has been shown
to be a potent inhibitor of this enzyme, thereby inhibiting
the formation of damaging leukotrienes.12
Free radical damage to membrane structures due to organic
disease or toxic chemicals results in increased release of
fatty acids. This leads, among other things, to increased
leukotriene synthesis and inflammation. Silymarin counteracts
this deleterious process by suppressing the pathological decomposition
of membrane lipids and inhibiting leukotriene formation and
inflammation.13
The protective effect of silymarin against liver damage has
been demonstrated in a number of experimental and clinical
studies. 1-36 Experimental liver damage in animals can be
produced by such diverse toxic chemicals as carbon tetrachloride,
galactosamine, ethanol, and praseodymium nitrate. Silymarin
has been shown to protect the liver from all of these toxins.1-6,8,14
Perhaps the most impressive of silymarin's protective effects
is against the severe poisoning of Amanita phalloides (the
deathcap or toadstool mushroom), an effect that has long been
recognized in folk medicine.6-8 Ingestion of Amanita phalloides
or its toxins causes severe poisoning and, in approximately
30 percent of victims, death.
Among the experimental models for measuring protection against
liver damage, those based on amanitin or phalloidin toxicity
are the most important, because these two peptides from Amanita
phalloides are the most powerful liver-damaging substances
known. Silymarin has demonstrated impressive results in these
experimental models. When silymarin was administered before
amanita toxin poisoning, it was 100 percent effective in preventing
toxicity.6,8 Even if given 10 minutes after the amanita toxin,
it completely counteracted the toxic effects. If given within
24 hours, silymarin would still prevent death and greatly
reduce the amount of liver damage.7
Perhaps the most interesting effect of Milk Thistle components
on the liver is their ability to stimulate protein synthesis.5,15,16
This stimulation results in an increase in the production
of new liver cells to replace the damaged old ones. Interestingly
enough, silymarin does not have a stimulatory effect on malignant
liver tissue. 15
From the above-described actions, it is apparent that Milk
Thistle, and more specifically silymarin, exerts both a protective
and restorative effect on the liver.
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Clinical applications
Obviously, silymarin is useful as an aid to the liver. It
can be used to support detoxification reactions or in the
treatment of more severe liver disease.
In numerous clinical studies, silymarin has been shown to
have positive effects in treating several types of liver disease,
including cirrhosis, chronic hepatitis, fatty infiltration
of the liver (chemicaland alcohol-induced fatty liver), subclinical
cholestasis of pregnancy, and cholangitis and pericholangitis.17-35
The therapeutic effect of silymarin in these disorders has
been confirmed by histological, clinical, and laboratory data.
Silymarin may also be useful in improving the solubility of
the bile in the treatment of gallstones and in psoriasis.
The therapeutic effect of silymarin in these disorders is
described below, along with a discussion on a new form of
silymarin (phosphatidylcholine-bound silymarin) and its clinical
effects.
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Chemical-induced liver damage
In one of the first extensive double-blind clinical trials
investigating silymarin's therapeutic effect in liver disorders,
silymarin demonstrated impressive results in 129 patients
with toxic metabolic liver damage, fatty degeneration of the
liver of various origins, or chronic hepatitis, as compared
with a control group composed of fifty-six patients. The results
might have been even more impressive if the study had lasted
longer than 35 days.17
A follow-up study of patients with liver damage due to alcohol,
diabetes, viruses, or toxic exposure demonstrated even more
striking results. Patients were followed for a long period
of time (e.g., 7 weeks). Not only were clinical findings markedly
improved in the silymarin-treated groups, but laboratory and
liver biopsy data improved as well. Highly significant results
were obtained in brornsulfophthalein retention, SGPT, iron,
and cholesterol levels. There were remarkable tissue restorative
effects as evidenced by biopsy. On completion of silymarin
therapy, the liver showed restitution of normal cell structure,
even in severely damaged livers. These effects on the tissue
level correlated well with improvements in blood chemistry.18
A more recent study highlights the benefit of silymarin in
individuals exposed to toxic chemicals. In the study, abnormal
results of liver function tests (elevated levels of two liver
enzymes, AST and ALT activity) and/or abnormal hematological
values (low platelet counts, increased white blood cell counts,
and a relative increase in lymphocytes compared to other white
blood cells) were observed in 49 of 200 workers exposed to
toxic toluene and/or xylene vapors for 5-20 years. Thirty
of the affected workers were treated with silymarin, the remaining
nineteen were left without treatment. Under the influence
of silymarin the liver function tests and the platelet counts
significantly improved. The white blood counts also showed
a nonsignificant tendency toward improvement.
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Cirrhosis
As described above, silymarin is quite effective in treating
alcohol-related liver disease. There is a tremendous range
in severity of alcohol-related liver disease, from relatively
mild to serious damage. Serious damage to the liver results
in cirrhosis-severe scarring (fibrosis). Even in this severe
state, silymarin has shown benefit. Perhaps the most significant
benefit is to extend the life span of these patients.
In one study, eighty-seven cirrhotics (forty-six with alcoholic
cirrhosis) received silymarin, while eighty-three cirrhotics
(forty-five with alcoholic cirrhosis) received a placebo.
The mean observation period was 41 months. In the treatment
group, there were twenty-four deaths with eighteen related
to liver disease; among the controls, there were thirty-seven
deaths with thirtyone related to liver disease. The 4-year
survival rate was 58 percent in the treatment group compared
to 39 percent in the controls.
Silymarin can also improve immune function in patients with
cirrhosis .32 Whether this effect is involved in the hepatoprotective
action or a result of improved liver function has yet to be
determined.
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Viral hepatitis
Silymarin is also useful in treating viral-induced liver
damage. It is effective in both acute and chronic viral hepatitis.
In a study of acute viral hepatitis, silymarin administered
to twenty nine patients showed a definite therapeutic influence
on the characteristic increased serum levels of bilirubin
and liver enzymes compared with a placebo group. The laboratory
parameters in the silymarin group regressed more than in the
placebo group after the fifth day of treatment. The number
of patients having attained normal liver values after 3 weeks'
treatment was significantly higher in the silymarin group
than in the placebo group.
In a study in chronic viral hepatitis, silymarin was shown
to result in dramatic improvement. Used at a high dose (420
milligrams of silymarin) for periods of 3 to 12 months, silymarin
resulted in a reversal of liver cell damage (as noted by biopsy),
an increase in protein level in the blood, and a lowering
of liver enzymes. Common symptoms of hepatitis (e.g., abdominal
discomfort, decreased appetite, and fatigue) were all improved.34
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Gallstones
Silymarin may help prevent or treat gallstones via its ability
to increase the solubility of the bile, according to the results
of a recent study.31 In the study, the composition of the
bile was assayed in nineteen patients with a history of gallstones
(four) or removal of the gallbladder due to gallstones (fifteen)
before and after silymarin (420 milligrams per day for 30
days) or placebo. Silymarin treatment led to significant reduction
in the biliary cholesterol concentration and bile saturation
index.
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Silymarin in psoriasis
Correction of abnormal liver function is indicated in the
treatment of psoriasis. Silymarin has been reported to be
of value in the treatment of psoriasis, and this may be due
to its ability to inhibit the synthesis of leukotrienes, and
improve liver function. 36,37
The connection between the liver and psoriasis relates to
one of the liver's basic tasks-filtering the blood. Psoriasis
has been shown to be linked to high levels of circulating
endotoxins, such as those found in the cell walls of gut bacteria.
If the liver is overwhelmed by an increased number of endotoxins
or chemical toxins, or if the liver's functional ability to
filter and detoxify is decreased, the psoriasis gets much
worse.
Another factor in psoriasis is excessive production of leukotrienes.
Silymarin has been shown to reduce leukotriene formation by
inhibiting lipoxygenase.12 Therefore, silymarin would inhibit
one of the causes of the excessive cellular replication.
Silymarin has other effects that would be of value in patients
with psoriasis. Most of these effects revolve around correcting
the abnormal cAMP-tocGMP ratio observed in the skin of patients
with psoriasis. The ratio of these two cellular control agents
controls cellular replication. In psoriasis, cGMP levels are
high in ratio to cAMP levels. Silymarin works to lower cGMP
levels while raising cAMP levels.36
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Silymarin bound to phosphatidylcholine
Recently, a new form of silymarin has emerged that may provide
the greatest benefit. The new form binds silymarin to phosphatidylcholine,
the key component of cellular membranes throughout our bodies.
Preliminary research indicates that bound silymarin is absorbed
better and produces better clinical results.
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Absorption studies with phosphatidylcholine-bound
silymarin
Several human and animal studies have shown that phosphatidylcholine-bound
silymarin is better absorbed. In one study, the excretion
of silybin, the major component of silymarin, in the bile
was evaluated in patients undergoing gallbladder removal (cholecystectomy).
A special drainage tube, the T-tube, was used to obtain the
samples of bile necessary. Patients were given either a single
oral dose of the silymarin-phosphatidylcholine complex or
silymarin. The amount of silybin recovered in the bile in
free and conjugated form within 48 hours was 11 percent for
the silymarin-phosphatidylcholine group and 3 percent for
the silymarin group.38
One of the significant features of this study is the fact
that silymarin has been shown to improve the solubility of
the bile. Since more silymarin is being delivered to the liver
and gallbladder when the phosphatidylcholine-bound silymarin
is used, this form is ideal for individuals with gallstones
or fatty infiltration of the liver-two conditions characterized
by decreased bile solubility.
In another study designed to assess the absorption of silymarin
bound to phosphatidylcholine, plasma silybin levels were determined
after administration of single oral doses of silymarin-phosphatidylcholine
complex and a similar amount of silymarin to nine healthy
volunteers. Although absorption was rapid with both preparations,
the bioavailability of the silymarin-phosphatidylcholine complex
was much greater than that of silymarin, as indicated by higher
plasma silybin levels at all sampling times after intake of
the complex. The authors concluded that complexation with
phosphatidylcholine greatly increases the oral bioavailability
of silymarin, probably by facilitating its passage across
the gastrointestinal mucosa.39
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Clinical studies with phosphatidylcholine-bound
silymarin
Several clinical studies have also shown phosphatidylcholine-bound
silymarin to be more effective. In one study, eight patients
with chronic viral hepatitis (three with hepatitis B, three
with both hepatitis B and hepatitis C, and two with hepatitis
C were given one capsule of phosphatidylcholine-bound silymarin
(equivalent to 140 milligrams of silymarin) between meals
for 2 months.40 After treatment, serum malondialdehyde levels
(an indicator of lipid peroxidation) decreased by 36 percent,
and the quantitative liver function evaluation, as expressed
by galactose elimination capacity increased by 15 percent.
A statistically significant reduction of liver enzymes was
also seen: AST decreased by 17 percent and ALT decreased by
16 percent.
In another study designed primarily to evaluate the dose-response
relationship of phosphatidylcholine-bound silymarin, positive
effects were again displayed.41 In the study, patients with
chronic hepatitis due to either a virus or alcohol were given
different doses: twenty patients received 80 milligrams twice
daily, twenty patients received 120 milligrams twice daily,
and twenty patients received 120 milligrams three times daily
for 2 weeks. At all tested doses, phosphatidylcholine-bound
silymarin produced a remarkable and statistically significant
decrease of mean serum and total bilirubin levels. When used
at the dosage of 240 or 360 milligrams per day, it also resulted
in a remarkable and statistically significant decrease in
ALT and GGTP liver enzymes. These results indicate that even
short-term treatment of viral or alcohol-induced hepatitis
with relative low doses of phosphatidylcholine-bound silymarin
can be effective, but for the best results higher doses are
indicated.
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Dosage
The standard dose of Milk Thistle is based on its silymarin
content (70-210 milligrams three times daily). For this reason,
standardized extracts are preferred. The best results are
achieved at higher dosages, that is, 140 milligrams of silymarin
three times daily.
The dosage for silymarin bound to phosphatidylcholine is
100 milligrams to 200 milligrams twice daily.
Webmaster's note: this would
be measured as silybin which means you would need to multiply
by three to get the actual amount of product taken. This is
why the recommended dosage of Maximum Milk Thistle™ (silybin
bound to phosphatidylcholine) is 240mg three times a day.
Alcohol-based extracts are virtually always contraindicated,
due to the need to administer relatively high amounts of alcohol
in order to obtain an adequate dose of silymarin.
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Toxicity
Silymarin preparations are widely used medications in Europe,
where a considerable body of evidence points to very low toxicity.1
When used at high doses for short periods of time, silymarin
given by various routes to mice, rats, rabbits, and dogs has
shown no toxic effects. Studies in rats receiving silymarin
for protracted periods have also demonstrated a complete lack
of toxicity.1
As silymarin possesses choleretic activity, it may produce
a looser stool as a result of increased bile flow and secretion.
If higher doses are used, it may be appropriate to use bile-sequestering
fiber compounds (e.g., guar gum, pectin, psyllium, and oat
bran) to prevent mucosal irritation and loose stools. Because
of silymarin lack of toxicity, long-term use is feasible when
necessary.
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References
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