Common names: Marian Thistle, Mary thistle, Marian,
Our Lady's thistle and St. Mary's silybum.
Silybum marianum family encompasses daisies and
thistles, including the common thistle and artichoke.
Milk thistle is native to the Mediterranean region
but also grows in many parts of Europe and America.
Concentrations of silymarin are highest in the fruit
of the plant, as well as in the seeds and leaves.
The active extract of milk thistle is silymarin, a mixture of the flavonolignans, including silydianin, silychristin and silybin.
Most commercial preparations of milk thistle are standardized to contain at least 70% of silymarin.
The compounds of milk thistle are known as Cardui Mariae Herba and Cardui Maria Fructus. Cardui Mariae Herba is absent of silymarin, which is only localized in the seed case. Cardui Maria Fructus contains silymarin.
Silymarin acts as an antagonist in many experimental liver damage models.
Silymarin may alter the structure of the outer cell membrane of hepatocytes to prevent penetration of liver poisons into the interior of the cell.
Silymarin may stimulate the action of nucleolar polymerase A, resulting in an increase in ribosomal protein synthesis, thereby stimulating the regenerative ability of the liver and the formation of new hepatocytes.
Silybin, the active constituent of silymarin has been reported to work as an antioxidant, scavenging free radicals.
Liver Disease: It is hypothesized that silymarin and its active constituent, silybin, derived from milk thistle, functions as an antioxidant and inhibits lipid peroxidation. It may increase hepatocyte protein synthesis by stimulating the activity of ribosomal RNA polymerase. It may decrease the activity of tumor promoters and stabilize mast cells. Silybin may protect against radiation-induced suppression of hepatic and splenic DNA and RNA synthesis and may slow calcium metabolism.
A study was conducted on 170 patients with alcoholic and non-alcoholic cirrhosis. Subjects were given either 140 mg of silymarin three times daily or placebo for a 41 month observation period. The 4-year survival rate was 58% ± 9% in the silymarin treated group and 39 ± 9% in the placebo group. The results suggested that patient mortality might have been reduced with treatment of silymarin. This effect was found to be more pronounced in patients with alcoholic cirrhosis.4
A review evaluated effectiveness of silymarin in improving clinical courses of various types of hepatitis. The studies evaluated varied in the number of patients enrolled, the type of animals used and dosing. In human trials, silymarin dosing ranged from 140 mg twice to three times a day and up to 560 mg a day vs. placebo, lasting from 3 weeks to 12 months. The studies were found to be difficult to interpret due to many inconsistencies. Overall, researchers did not find silymarin to have any adverse side effects. It may be effective in improving the clinical courses of both acute and chronic, viral, drug and toxin-induced and alcoholic hepatitis, but better designed trials are needed.5
A large collaborative study on use of milk thistle therapy for patients with hepatitis C is ongoing through the National Institute of Allergy and Infectious Diseases (NIAID) and the National Institute of Diabetes and Kidney Diseases (NIDKD). Research updates are available online at www.nccam.nih.gov.
Antioxidant: The potential usefulness of antioxidants as anticarcinogenic agents is based on the putative role of oxidative stress, reactive oxygen species, and free radicals in carcinogenesis. Silymarin, and its component silibinin or silybin, may act as strong antioxidants, capable of scavenging both free radicals and reactive oxygen species.
A study assessing the inhibitory effect of silibinin and silymarin on carcinoma cell growth was done. Human prostate, breast and cervical carcinoma cells were treated with either ethanol or 100 mg of silibinin or silymarin for five days. Both silibinin and silymarin showed profound cell growth inhibition. Five days after treatment, silibinin showed a statistically significant growth inhibition of prostate carcinoma cells (70% inhibition), cervical carcinoma cells (71% inhibition) and breast carcinoma cells (72% inhibition). Overall, researchers found that anticarcinogenic effects of silymarin are due to the main constituent, silibinin. More detailed studies are needed to develop this active constituent of milk thistle as a cancer chemopreventive and anticarcinogenic agent.6
Another study was performed on mouse skins to look at antitumor effect of silymarin. Six groups were treated with either acetone or 3, 6 and 12 mg doses of silymarin per application at various times for a total of 20 weeks. Results suggested that silymarin possessed exceptionally high protective effects against tumor promotion, primarily targeted against stage 1 tumors. The mechanism of such effects may involve inhibition of promoter-induced edema, hyperplasia, proliferation index and oxidant state.7
UVB Skin Cancer: Non-melanoma skin cancer is the most common cancer among humans and solar UV is the major cause. Silymarin may be protective against UVB radiation-induced non-melanoma skin cancer.
Mice subjected to UVB-induced tumors were divided into control and treatment groups. The silymarin group was treated with 9 mg of silymarin, applied topically before UVB exposure. Overall, silymarin was found to provide substantial protection against different stages of UVB- induced carcinogenesis, possibly via its strong antioxidant properties.8
123 Milk
thistle may protect against the liver toxicity or liver damage sometimes caused
by antipsychotic drugs, such as chlorpromazine [Thorazine ] and thioridazine
[Mellaril ]. It is advisable to consult a physician or pharmacist if this
combination is considered.
Information on the relationship between substances and disease is provided
for general information, in order to convey a balanced review of the scientific
literature. In many cases the relationship between a substance and a disease is
tentative and additional research is needed to confirm such a
relationship.
The dietary supplement information contained on this site has been compiled from published sources thought to be reliable, but it cannot be guaranteed. Efforts have been made to assure this information is accurate and current. However, some of this information may be purported or outdated due to ongoing research or discoveries. The authors, editors and publishers cannot accept responsibility for errors or omissions or for any consequences from applications of the information in this site and make no warranty, expressed or implied, with respect to the contents herein.
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