Just published randomized controlled clinical trial

Huseini HF, Larijani B, Heshmat R, Fakhrzadeh H, Radjabipour B, Toliat
T, Raza M.
The efficacy of Silybum marianum (L.) Gaertn. (silymarin) in the
treatment of type II diabetes: a randomized, double-blind,
placebo-controlled, clinical trial.
Phytother Res. 2006 Dec;20(12):1036-9. PMID: 17072885 [PubMed - in
process].
<http://www3.interscience.wiley.com/cgi-bin/abstract/113445765/ABSTRACT>

found that milk thistle extract silymarin reduced statistically
significantly HbA(1)c, FBS, total cholesterol, LDL, triglyceride SGOT
and SGPT levels in type 2 diabetes patients. Here's the abstract of
the study:

   "Oxidative stresses are increasingly implicated in the
   pathogenesis of diabetic complications which may either cause
   direct pancreatic beta-cell damage or lead to metabolic
   abnormalities that can induce or aggravate diabetes. The
   valuable effect of antioxidant nutrients on the glycemic control
   of diabetic patients has been reported in experimental and
   clinical studies. The present study was designed to investigate
   the effects of the herbal medicine, Silybum marianum seed
   extract (silymarin), which is known to have antioxidant
   properties on the glycemic profile in diabetic patients. A 4-
   month randomized double-blind clinical trial was conducted in 51
   type II diabetic patients in two well-matched groups. The first
   group (n = 25) received a silymarin (200 mg) tablet 3 times a
   day plus conventional therapy. The second group (n = 26)
   received the same therapy but a placebo tablet instead of
   silymarin. The patients were visited monthly and glycosylated
   hemoglobin (HbA(1)c), fasting blood glucose (FBS), insulin,
   total cholesterol, LDL and HDL, triglyceride, SGOT and SGPT
   levels were determined at the beginning and the end of the
   study. The results showed a significant decrease in HbA(1)c,
   FBS, total cholesterol, LDL, triglyceride SGOT and SGPT levels
   in silymarin treated patients compared with placebo as well as
   with values at the beginning of the study in each group. In
   conclusion, silymarin treatment in type II diabetic patients for
   4 months has a beneficial effect on improving the glycemic
   profile."