Silymarin, an antioxidant flavonoid complex derived from the herb milk thistle (Silybum marianum), has long been used as a liver tonic. Two new studies show that it can reduce insulin resistance (the underpinning of adult-onset diabetes, hypertension, and hypercholesterolemia) and diabetic complications. A third study reports that it may have some anti-cancer benefits as well.

Mario Velussi, MD, and his colleagues at the Monfalcone Hospital, Gorizia, Italy, treated 60 diabetic patients with either 600 mg of silymarin or placebo daily for 12 months. The patients had non-insulin-dependent diabetes (NIDDM), were suffering from alcoholic cirrhosis (alcohol-induced liver damage), and had been receiving insulin therapy for at least two years.

“Insulin resistance is constantly fairly high in patients with NIDDM and hepatic cirrhosis,” Velussi wrote in the Journal of Hepatology (1997;26:871-9). “This metabolic disorder is partly related to increased blood glucose levels due to reduced glucose uptake by the liver. Hyperglycemia promotes hyperinsulinemia and this, together with the decreased hepatic degradation of the insulin molecule, may lead to insulin resistance in the target tissues.”

Velussi used silymarin because research has shown it to be a powerful antioxidant with a long history of use in treating liver disorders.

After 12 months, the results of silymarin therapy were dramatic. Although fasting glucose levels rose slightly during the first month of use, they subsequently showed a progressive and significant decline, going from an average of 190 mg/dl to 174 mg/dl. In addition, average daily glucose levels dropped from 202 mg/dl to 172 mg/dl.

Although such decreases in blood sugar might raise concerns about hypoglycemia, the patients treated with silymarin did not have any increase in the number of mild or severe hypoglycemic episodes, suggesting that silymarin stabilized as well as lowered glucose levels.

The silymarin-treated patients had still other benefits. Their glucosuria (sugar in urine) decreased from an average of 37 grams/day to 22 grams/day. Glycosylated hemoglobin levels decreased significantly, indicating improved overall glucose control. Their average daily insulin requirement also decreased during the study, going from 55 IU to 42 IU daily.

In addition, SGOT and SGPT values declined significantly in the patients taking silymarin, confirming that liver function improved. There was also a decrease in blood levels of malondialdehyde, a marker of free radical damage, approaching that of healthy subjects. By all measures, the placebo group did not improve.

In a separate cell-culture study, German researchers found that a specific silymarin flavonoid, silybinin, prevented the accumulation of fibronectin protein in kidney cells. Fibronectin is one of the principal causes of kidney damage in diabetics.

Simone Wenzel, PhD, of Justus-Liebig University, Germany, incubated human mesangial cells (HMCs, a type of kidney cell) in a high concentrations of glucose or a combination of glucose and silybinin for eight days.

According to Wenzel’s article in the Journal of Pharmacology and Experimental Therapeutics (1996;279:1520-6), the silybinin prevented the accumulation of fibronectin. Wenzel believed that silybinin’s protective effect was the result of its antioxidant properties. Malondialdehyde, an marker of free radical damage to fats, increased only in cells not treated with silybinin.

Finally, researchers from Case Western Reserve University, Cleveland, reported that silymarin slowed the growth of human cancer cells. In a cell-culture study, Rajesh Agarwal, PhD, and his collaborators determined that silymarin inhibited epidermal growth factor cell receptors, a type of tyrosine kinase receptor that promotes tumor growth.

“Silymarin treatment also resulted in a highly significant inhibition of cell growth and proliferation,” Agarwal wrote in the Journal of Investigative Dermatology (1997;108:547, #60). “Treatment of cells with other antioxidant-like green tea polyphenols, EGCG [epigallocatechin gallate], quercetin, curcumin and genistein, also resulted in similar inhibitory effects albeit at different levels.”

This article originally appeared in The Nutrition Reporterâ„¢ newsletter. The information provided by Jack Challem and The Nutrition Reporterâ„¢ newsletter is strictly educational and not intended as medical advice. For diagnosis and treatment, consult your physician.