Jean Hofve, DVM
Whole Dog Journal
Volume 5, Number 7, July 2002
This amazing herb is used to treat diabetes, liver failure, and IBD.
Milk thistle can be purchased in powder, capsule, and liquid extract form.
Milk thistle (Silybum marianum) is a flowering plant in the Aster family. A
native of Europe, it has been used since the time of the Roman emperors as a
liver tonic. Milk thistle is one of very few traditionally used herbs that has
been widely accepted by conventional science to have significant medicinal
Today we know the active ingredient of milk thistle seed extract as a flavonoid
compound called “silymarin.” Most milk thistle extracts available today contain
about 80 percent silymarin.
Uses in canines
Silymarin, which is itself a combination of several other active compounds, has
been extensively studied around the world, and has been shown to be safe and
effective in treating a variety of liver diseases and other conditions. It
specifically protects the liver against toxins (including some drugs and heavy
metals), activates protein synthesis, and stimulates growth of new liver cells
to replace those that are dead or damaged. Milk thistle also has strong
antioxidant (destroys oxygen free radicals) and anti-inflammatory actions.
Silymarin reaches high levels in the bile and liver (it also reaches significant
levels in the lungs, pancreas, prostate, and skin). It can be used in the
treatment of hepatic lipidosis, chronic hepatitis, cholangitis (inflammation of
the bile ducts), and pericholangitis (inflammation of the tissue around the bile
ducts). It may be useful in preventing or treating gallstones by thinning the
bile. Many dogs with inflammatory bowel disease (IBD) have concurrent
inflammation of the liver/bile system and the pancreas. This suite of symptoms
is called “triaditis.” Because milk thistle’s beneficial actions concentrate on
the liver and bile systems, it may also be helpful in dogs with IBD.
Milk thistle should be considered as an aid to healing after drug therapy,
vaccinations, and infections such as canine parvovirus, as well as an potential
adjunct treatment for cancer. Researchers at Case Western University concluded
from their work that “silymarin possesses exceptionally high protective effects
against tumor promotion . . . ” One human study even suggests a role for milk
thistle in diabetes mellitus through its normalizing effects on red blood cells.
It may also help prevent diabetic neuropathy, a common complication of the
disease that causes degeneration of the nerves controlling the hind limbs, which
consequently produces weakness and an abnormal gait.
Milk thistle generally supports the immune system through its powerful
antioxidant, free-radical scavenging action, its ability to preserve the supply
of another important antioxidant, glutathione, as well as direct effects on
immune cells. Glutathione, which is stored primarily in the liver, naturally
declines over time, and depletion of this protein appears to accelerate the
While it’s not exactly the fountain of youth, milk thistle clearly has
wide-ranging positive effects throughout the body. However, before you add this
potent herb to your dog’s daily regimen “just in case” it might do some good,
it’s important to consider that some herbalists believe milk thistle is best
reserved as a treatment for existing disease, rather than being used by itself
in a healthy dog.
While moderate use of milk thistle is very safe, there is some experimental
evidence to suggest that long-term ingestion of very high dosages of milk
thistle will eventually suppress liver function.
Dosage and administration
The standard dosage of milk thistle extract is based on a silymarin content of
around 80 percent; most supplements contain anywhere from 50-500 milligrams (175
mg is typical). As with many supplements, it’s probably better to buy a milk
thistle derivative rather than a silymarin-only or other fractional supplement,
since there may be other compounds found in the whole herb that significantly
enhance the effects of what science has decided is the main player.
Because of its excellent safety record and lack of adverse drug interactions,
when I’m treating a very sick dog with advanced liver disease, I do not hesitate
to use up to 200 mg per 10 pounds of body weight of milk thistle extract daily.
For most canine purposes, however, one-third to one-half of that dose is more
than adequate. (Dogs with liver disease typically will not eat, but it’s a
simple matter to open up a capsule, mix the appropriate amount of powdered herb
with a little blenderized food or baby food, and feed it to the dog in a
syringe.) Too high a dose can cause an upset tummy, gas, or mild diarrhea; these
are easily resolved by giving less.
Human research studies have shown that it is more effective to administer this
herb in three or four small portions over the day than in one large daily dose.
When it is not possible to split the daily dose and administer the fractional
portions three or four times a day, give it at least twice a day.
The capsule form is easy to find – any health food store, and even most
pharmacies and grocers, will have them in stock. The herb also comes in a liquid
extract, but most human products contain a fair bit of alcohol. If you prefer a
liquid preparation, get one specifically intended for use in animals.
Dr. Dodds recommends using milk thistle in the doses listed below to help heal the liver
along with reducing phenobarbital (according to your vet) and
feeding the liver cleansing diet.
Milk Thistle Dosage (from the newsletter "Healthy Pets -
|Dose as % of
adult human dose