New clinical uses for milk thistle? - Phytotherapy Review & Commentary

Townsend Letter for Doctors and Patients,  June, 2003  by Kerry Bone

• E-mail
• Print
• Link

A group of Italian scientists investigated the iron-binding capacity of silybin, a component of the complex of flavanolignans known as silymarin found in milk thistle (Silybum marianum). (1) Their motivation in doing so was to find an orally-active, non-toxic alternative to the iron-binding synthetic drug desferrioxamine, which causes side effects such as bone deformities, sensory abnormalities and cerebral toxicity. Desferrioxamine, which must be administered by injection, is currently the treatment of choice for the iron overload which can follow transfusion therapy for Cooley's anaemia ([beta]-thalassaemia major). The scientists found that silybin strongly binds the ferric ion (Fe(III)), even at acidic pH. The complex of this molecule with iron demonstrated remarkable stability.

Insulin-resistance and the associated conditions of metabolic syndrome X and type I diabetes are becoming increasingly prevalent in modern communities. In this context a clinical trial published in 1997 should be revisited. The aim of the study was to determine if long-term treatment with the silymarin complex from milk thistle was effective in reducing lipid peroxidation and insulin resistance in diabetic patients with cirrhosis. (2) A 12-month open, controlled study was conducted in two well-matched groups of insulin-treated diabetics with alcoholic cirrhosis. One group (n=30) received 600 mg silymarin per day plus standard therapy, while the control group (n=30) received standard therapy alone. The efficacy parameters, measured regularly during the study, included fasting blood glucose levels, mean daily blood glucose levels, daily glucosuria levels, glycosylated hemoglobin (HbA1c) and malondialdehyde levels. There was a significant decrease (p<0.0l) in fasting blood glucose levels, mean daily blood glucos e levels, daily glucosuria and HbA1c levels already after 4 months of treatment in the silymarin group. In addition, there was a significant decrease (p<0.0l) in fasting insulin levels and mean exogenous insulin requirements in the treated group, while the untreated group showed a significant increase (p<0.05) in fasting insulin levels and a stabilized insulin need. These findings are consistent with the significant decrease (p<0.0l) in basal and glucagon-stimulated C-peptide levels (an indicator of endogenous insulin production) in the treated group and the significant increase in both parameters in the control group. Another interesting finding was the significant decrease (p<0.0l) in malondialdehyde levels observed in the treated group. These results show that treatment with silymarin may reduce the lipoperoxidation of cell membranes and insulin resistance, significantly decreasing endogenous insulin overproduction and the need for exogenous insulin administration.

Commentary

For some time I have been treating patients with the iron-storage disease haemochromatosis with relatively high doses of milk thistle extract (3 to 4 tablets per day containing 200 mg of extract standardized to 168 mg of silymarin). My motive in doing so was to protect the liver against the oxidative damage caused by iron accumulation in that organ. However, the above study suggests that there could be significant additional benefits from milk thistle in this disease. If milk thistle tablets are taken with meals they will inhibit iron absorption, but also the capacity of silybin to strongly bind iron suggests that milk thistle therapy could also facilitate the removal of iron from tissues. The next question to be answered is how strongly silybin might also bind heavy metals such as lead, cadmium and mercury.

The capacity of milk thistle to reduce insulin resistance could be a huge development in the therapy for this major health issue. However, this finding needs to be confirmed in patients with type II diabetes who do not also have alcoholic cirrhosis.

Incidentally, a recent rat study found that silymarin had significant estrogenic activity. (3) Will this versatile herb also find a role in the management of menopausal symptoms?

(1.) Borsari M, Gabbi C, Ghelfi A et al. Silybin, a new iron-chelating agent. J Inorg Biochem 2001; 85: 123-129

(2.) Velussi M, Cernigoi AM, De Monte A et al. Long-term (12 months) treatment with an anti-oxidant drug (silymarin) is effective an hyperineulinemia, exogenous insulin need and malondialdehyde levels in cirrhotic diabetic patients. J Hepatol 1997; 26(4):871-879

(3.) Kummer V, Maskova J, Canderle J et al. Estrogenic effects of silymarin in ovariectomized rats. Vet Med - Czech 2001; 46(1): 17-23

COPYRIGHT 2003 The Townsend Letter Group
COPYRIGHT 2003 Gale Group