The liver performs a variety of functions that are vital to good health. Aside from being the body's built-in filtration system, the liver regulates glucose metabolism, blood clotting and bile production. In dogs, the onset of liver disease may follow toxin overload due to a genetic disorder or bacterial infection. Fortunately, the liver can repair itself with nutritional support. In addition to dietary measures, many holistic veterinarians recommend milk thistle for dogs with liver problems.
Milk thistle is a member of the daisy family recognised by a crown of thornlike leaves that support the base of its purple flower heads. For thousands of years, the milky sap obtained from the plant has been regarded as a liver and gallbladder "tonic." In 2010, milk thistle is cultivated for pharmaceutical use in its native England, as well as China, Germany, Poland, Austria, Hungary and Argentina.
The active constituent of milk thistle is silymarin, which actually represents a class of bioflavonoids that includes silibinin, silicristin and silidianin. According to the University of Maryland Medical Center, this compound exhibits two main actions on the liver. First, it stimulates the regeneration of cells damaged from toxins. Second, silymarin helps to protect new liver cells from becoming damaged by scavenging free radicals. This substance provides more antioxidant activity than vitamin E. Silymarin also reduces inflammation by blocking the production and release of inflammatory agents such as leukotrienes.
Milk thistle has also shown some antiviral and anti-cancer benefits. For instance, some studies indicate that silymarin prevents viral replication in infectious diseases of the liver, such as hepatitis C. Other studies suggest that silymarin may prevent the reproduction and spread of cancer cells by inducing apoptosis, or programmed cell-death.
Milk thistle is available as a liquid extract standardised to contain 70 to 80 per cent silymarin. Capsules of the powdered herb are standardised to contain 120 to 140 mg of silymarin.
According to Todd R. Tams, DVM, the typical veterinary dose of milk thistle for dogs with liver problems varies between 50 to 200 mg, given one or two times daily. Mike Richards, DVM, says that the average dose of milk thistle for dogs with liver problems is about one-quarter that of the manufacturer's recommended dose for a human adult, for a 50 pound dog. For chronic and advanced cases of liver disease, Jean Hofve, DVM, prescribes 200 mg of milk thistle extract for every 4.54 Kilogram of body weight.