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heblaj01 · 06-28-2006, 07:13 AM

Many in vitro & animal tests have attributed beneficial effects to milk thistle especially for various hepatic diseases. And two of its purified constituants,
silymarin and silibinin (the latter a major component of the former), have also been studied in particular for cancer.

However, the study shown below throws a cautionary warning about silymarin & by extension about milk thistle supplementation.

It should be noted that in the abstract on the silibin beneficial effect on lung cancer in mice the researchers specifically mentioned they did not use milk thisle but purified silibinin.
If these studies apply to humans, it would mean that milk thistle is a complex chemical with opposite properties as far as cancer is concerned.
It does point to the importance of purified chemicals in medical experiments to show non anbiguous results.
Enhancement of mammary carcinogenesis in two rodent models by silymarin dietary supplements.

Malewicz B, Wang Z, Jiang C, Guo J, Cleary MP, Grande JP, Lu J.

The Hormel Institute, University of Minnesota, 801 16th Avenue NE, Austin, MN 55912.

Silymarin is a mixture of polyphenolic flavonoids isolated from milk thistle (Silybum marianum) with anti-cancer activities reported in several organ sites. The present study tested the efficacy of dietary silymarin against mammary carcinogenesis in two rodent models. In the Sprague-Dawley rat model, female rats were fed a purified diet supplemented with none, 0.03, 0.1, 0.3 or 1% (w/w) of silymarin from 21 days of age (DOA) and carcinogenesis was initiated by a single i.p. injection of 1-methyl-1-nitrosourea (MNU) at 51 DOA. Mammary tumor (MT) development was followed till 110 days after carcinogen injection. In the MMTV-neu/HER2 transgenic mouse mammary carcinogenesis model, homozygous transgenic females were fed a purified diet supplemented with none or 0.3% silymarin, either from 28 or 120 DOA and MT development was followed to approximately 300 DOA. The results showed that dietary silymarin increased the plasma concentration of free and total silibinin, a major component of silymarin, in a dose-dependent manner in the rat, but did not decrease either MT incidence or number. Instead silymarin modestly increased the number of MNU-induced MTs in rats. Similarly, silymarin increased MT incidence and multiplicity and non-mammary tumors in the neu-transgenic mice. In cell culture, treatment of human MCF-7 breast cancer cells with serum achievable concentrations of silymarin in the rodent models stimulated their growth, in part through an estrogen-like activity. Because silymarin is being used in the treatment of liver cirrhosis and a variety of other human ailments, and is sold as a dietary supplement, our findings add a cautionary note to its application in breast cancer prevention.

06-28-2006, 07:13 AM	#3
heblaj01 Senior Member Join Date: Apr 2006 Posts: 543	Caution about milk thistle for cancer Many in vitro & animal tests have attributed beneficial effects to milk thistle especially for various hepatic diseases. And two of its purified constituants, silymarin and silibinin (the latter a major component of the former), have also been studied in particular for cancer. However, the study shown below throws a cautionary warning about silymarin & by extension about milk thistle supplementation. It should be noted that in the abstract on the silibin beneficial effect on lung cancer in mice the researchers specifically mentioned they did not use milk thisle but purified silibinin. If these studies apply to humans, it would mean that milk thistle is a complex chemical with opposite properties as far as cancer is concerned. It does point to the importance of purified chemicals in medical experiments to show non anbiguous results. Enhancement of mammary carcinogenesis in two rodent models by silymarin dietary supplements. Malewicz B, Wang Z, Jiang C, Guo J, Cleary MP, Grande JP, Lu J. The Hormel Institute, University of Minnesota, 801 16th Avenue NE, Austin, MN 55912. Silymarin is a mixture of polyphenolic flavonoids isolated from milk thistle (Silybum marianum) with anti-cancer activities reported in several organ sites. The present study tested the efficacy of dietary silymarin against mammary carcinogenesis in two rodent models. In the Sprague-Dawley rat model, female rats were fed a purified diet supplemented with none, 0.03, 0.1, 0.3 or 1% (w/w) of silymarin from 21 days of age (DOA) and carcinogenesis was initiated by a single i.p. injection of 1-methyl-1-nitrosourea (MNU) at 51 DOA. Mammary tumor (MT) development was followed till 110 days after carcinogen injection. In the MMTV-neu/HER2 transgenic mouse mammary carcinogenesis model, homozygous transgenic females were fed a purified diet supplemented with none or 0.3% silymarin, either from 28 or 120 DOA and MT development was followed to approximately 300 DOA. The results showed that dietary silymarin increased the plasma concentration of free and total silibinin, a major component of silymarin, in a dose-dependent manner in the rat, but did not decrease either MT incidence or number. Instead silymarin modestly increased the number of MNU-induced MTs in rats. Similarly, silymarin increased MT incidence and multiplicity and non-mammary tumors in the neu-transgenic mice. In cell culture, treatment of human MCF-7 breast cancer cells with serum achievable concentrations of silymarin in the rodent models stimulated their growth, in part through an estrogen-like activity. Because silymarin is being used in the treatment of liver cirrhosis and a variety of other human ailments, and is sold as a dietary supplement, our findings add a cautionary note to its application in breast cancer prevention.