Silymarin is a standardised extract of milk thistle seeds, which contains antioxidant and anti-inflammatory constituents.
Because oxidative stress plays a role in the pathophysiology of type 2 diabetes, it is biologically plausible that silymarin might improve the metabolic parameters of this disease.
Researchers conducted a randomised controlled trial to explore the effects of silymarin on glycaemic control and lipid profiles of patients with type 2 diabetes.
A total of 40 patients (with type 2 diabetes and taking oral hypoglycaemic medications) were randomised to take silymarin or placebo for 45 days. Silymarin (Livergol, manufactured by Goldaru Herbal Products Pharmaceutical Company in Iran) was standardised to 8.44% silymarin and 30.07% silybins and was dosed at 140 mg three times per day.
Results showed that silymarin significantly lowered fasting blood sugar, insulin, and Homeostasis Model Assessment-Insulin Resistance (HOMA-IR) and increased quantitative insulin sensitivity check index (QUICKI) in the intervention group as compared with baseline and a placebo.
In the intervention group, fasting blood sugar decreased by 11%, insulin decreased by 14 %, HOMA-IR decreased by 26%, and QUICKI increased by 6% after 45 days.
Results also showed that silymarin significantly reduced triglycerides and the triglyceride to HDL-cholesterol ratio and enhanced HDL-cholesterol as compared with the placebo.
Silymarin also significantly reduced total cholesterol and LDL-cholesterol as compared with baseline. In the intervention group, triglycerides decreased by 24%, total cholesterol decreased by 8%, LDL-cholesterol decreased by 7%, the triglyceride to HDL-cholesterol ratio decreased by 28%, and HDL-cholesterol increased by 7%.
Potential mechanisms to explain the effects of silymarin on glycemic control and lipid profiles include its ability to inhibit hepatic glucose production, inhibit fatty acid synthesis, block cholesterol absorption and increase fatty acid oxidation via peroxisome proliferator-activated receptor alpha (PPAR alpha). It is also possible that the antioxidant effects of silymarin support glycemic control.
Although the mechanisms are not entirely understood, the results of this study suggest that silymarin supports glycaemic control and metabolic function when given as adjunctive therapy with oral hypoglycaemic medications in type 2 diabetes.