Silybum Marianum – Milk Thistle

Milk thistle has become, over the last decade, one of the most commonly used herbs in natural veterinary medicine, addressing a whole host of issues most often related to active liver disease, or in hopes of slowing the likelihood of liver problems associated with longterm use of phenobarbitol in epileptic dogs. For humans too, milk thistle is a very popular remedy, used to offset the ill effects of alcohol abuse and acetaminophen and generally support liver health. Its antioxidant properties make it a good herb to consider in both cancer therapy and prevention; there are multiple uses, such as helping to control blood sugar spikes, that are not popularly associated with it but well worth investigation. As with even the safest of plants, some caution should be exercised with sensitive individuals; there are also interactions with certain drugs that should be borne in mind. Many researchers feel that longterm use of milk thistle can actually weaken liver function so recommend staggering the dose – 3- 6 weeks on, 1 – 3 weeks off . I’ve heard argument both for and against this practise and cannot find conclusive evidence, so my tendency is to err on the side of caution; I stagger the dose with all dogs in my care. But Silymarin is one of the best researched herbs we have, its safety and efficacy are well documented. below, a few aspects of this wonderful plant – history, how and when to use, and more.

Family: Asteraceae (Daisy, Sunflower family, sometimes called Compositae)

Distribution: widespread; indigenous to Southern and Western Europe, naturalized to North and South America

Common Names: Holy Thistle, Marian Thistle, St. Mary’s Thistle, Chardon-Marie, Mariendistel. In Chinese Medicine known as shu fei ji. Not to be confused with Blessed Thistle, Cnicus Benedictus.

Energetics: Various descriptions; primarly bitter, warming.

Constituents: Silymarin, a flavonoid complex comprised of silibinin, silidianin and silichristine. Most benefits of milk thistle derive from these three, probably primarily silibinin. Other constituents include sterols, lignans, mucilage, biogenic amines and other flavonoids.

Clinical Actions: Hepatoprotective, demulcent, antioxidant, cholagogue, galactagogue

Parts Used:Seed collected in late summer. Historically the leaves were eaten (in Europe) as a vegetable and the fruit a delicacy like artichoke. History and Traditional Usage:Milk thistle has a history of use that spans two millennia (as far as we know). Often thought of as simply a “liver herb” – and it is unparalleled in that regard – there is a great deal more to this herb than the protective and regenerative support it offers the liver.Mrs. Grieves tell us this: “Westmacott, writing in 1694, says of this Thistle: ‘It is a Friend to the Liver and Blood: the prickles cut off, they were formerly used to be boiled in the Spring and eaten with other herbs; but as the World decays, so doth the Use of good old things and others more delicate and less virtuous brought in.’ “ The use of Milk Thistle dates further back than Westacott. The first references I know of are from circa 25 AD, from the Roman naturalist Pliny the Elder, who tells us that “the juices will carry the bile”- the famed Roman Physician Dioscorides used the seeds “for infants, and against snakebite”. Gerard used milk thistle and considered it “ the best remedy for all melancholy diseases” which physicians at the time considered a liver complaint. Culpepper, the famous British herbalist who practised half a century later, used the name Our Lady’s thistle instead of Milk thistle. He recommended its use in the treatment of disorders affecting the liver and spleen, the kidney’s in provoking the flow of urine, to break and expel stones and also to treat dropsy. By the 19th century Milk thistle was commonly used by German physicians for the treatment of liver and blood problems, as well as for intestinal cleansing. Again the seeds were found to contain the active principle that has the specific effect on the liver. No mention of the plant exists in Native American herbology

Modern Application(human): Published research provides us with the following: Silymarin has the following effects and can be used for any or all of the following: – Antioxidant effect – inhibition of lipid peroxidation in hepatoctye plasma membranes, this inhibiting the action of multiple toxic agents – chelates iron and decreases glutathione destruction in iron overload conditions – stabilizes mast cells – slows calcium metabolism – decreases activity of tumor-promoting factor.Useful for liver disease: Useful in a wide range of hepatic disorders, including toxin and drug induced as well as viral hepatitis, alcoholic liver disease, and cirrhosis. Milk thistle decreases aminotransferase activity and improves clinical parameters consistently with all of these pathologies. Use in all acute and chronic cases with dosage appropriate to condition and duration of use.

Canine Applications


Liver Disease: protection against toxins, supports regeneration of healthy cells, anti-inflammatory; useful post-disease, vaccination or drug therapy  also for hepatitis, generalized inflammation, toxin recovery, portosystemic shunt – any and all liver disease of the canine

Kidney disease: In vitro, oxidative damage to kidney cells were reduced by silymarin. Worth adding to a renal protocol for human or canine.

Pancreatitis: Induced pancreatitis in rats was significantly ameliorated with silymarin (Soto, 1998). Should be used in cases of cyclosporine use,to protect pancreas from damage.

Cancer: May have value in prevention, especially prostate cancer. Use as a rotated antioxidant with ellagic acid, alpha-lipoic acid and COQ10.

Hyperlipidemia: Susan Wynn writes that “Animal studies have suggested that silymarin can help control blood lipid levels possibly by modulating absorption of cholesterol”. This response has not been noted in humans but it suggests an application for dogs with hyperlipidemia, such as miniature schnauzers and any diabetic dog.

Diabetes: helps prevent diabetic neuropathy in afflicted dogs

Personally, I use Milk Thistle in a variety of ways, both proactively (twice a year, a 6 week round of the standardized extract) and therapeutically, in all liver disorders, and with pancreatitis, cancer (according to type) and renal dysfunction. As always the herb should not be expected to compensate for a diet inappropriate for the condition so, adjustment of fats,carbohydrate and/or protein ,plus an emphasis on specific kinds of these nutrients, is always the bottom line of therapy. I never expect herbs to work optimally if the diet is working against the goals of the individual. Irrespective of diet I do however use MT in all cases of liver toxicity, poisoning, for hepatitis, and post- or during chemotherapy. My own senior dog is on 250 mgs of standardized extract TID and will remain so for the rest of her life, with “rests” of 3-4 weeks every few months. For me, milk thistle is indispensable for epileptic dogs on phenobarbitol as well. Most of the researchers I have looked at, including Susan Wynn DVM, Barbara Fougeres, co-author of the comprehensive Veterinary Herbal Medicine, Gregory Tilford and Mary Wulff-Tilford, authors of the classic Herbs for Pets and all related independent studies, suggest that milk thistle should not be used on a daily basis, despite it’s marvelous healing properties. The Tilfords write that “milk thistle is a medicine that is best reserved for situations where the liver is under abnormal stress”. I can’t say I agree 100% with this;  I would say that dosage and duration depends on multiple factors and while I would use high doses for any acute case of poisoning or other acute liver distress, I have used it longer-term for a variety of conditions – with the qualifier I do give a “rest” every2-3 months for several weeks in these cases.

Toxicology: Relatively non-toxic and safe – if any reaction occurs it is most often allergic or gastrointestinal. For this reason I always recommend small initial doses and a build up to therapeutic levels. Susan Wynn has noted two cases in which supplemental milk thistle was associated with an elevation in ALT levels; given the very small number of cases in which this occurred it is believed to have been an allergic reaction. Since silymarin stimulates liver and gallbladder activity, increasing bile secretion, it may have a mild, transient (2-3 days) laxative effect in some individuals. Allergic reaction is rare; however, it should not be used by people with hypersensitivity to it or other plants in the Asteraceae family (e.g. ragweed). Other rare associated effects include GI upset, headache, rash, insomnia and malaise.

Drug Interactions: Milk thistle may reduce the insulin requirement for diabetic dogs due to it’s capacity to lower blood sugar levels: it has also been shown to protect organs when the patient is taking cisplatin, acetaminophen, butyrophenones, halothane, phenothiazines, tacrine and vincristine.People using antipsychotic medications, yohimbine, or male hormones such as testosterone should not take milk thistle. J.P. Haas, MD tells us this: Indinavir – There have been reports that milk thistle interferes with the disposition of the HIV protease inhibitor indinavir. However, Piscitelli et al. (2002) determined that 175 mg doses of milk thistle taken three times daily did not significantly interfere with indinavir levels. Cytochrome p450 – Some studies have suggested possible interaction with certain medications due to milk thistle’s utilization of cytochrome p450 pathways. Milk thistle was studied in relation to known cytochrome p450 inducers (rifampin) and inhibitors (clarithromycin) and was found not to have a significant effect of CYP3A (Gurley et al. 2006).

Preparation A variety of methods are useful for this herb, although this writer prefers dried standardized extract for the canine. Alcohol tincture may also be used; glycerite is usually easier to get the canine to accept but it is more difficult to extract the active constituents in glycerin or low alcohol.,as dogs dislike the taste of the alcohol tincture so much I generally use a standardized powder extract. It’s important to note in cases of acute liver disease with smaller dogs, adding alcohol might not be wise!

Dosage: Of the standardized extract (powder) I use 2- 5 mgs. per lb BW, 2 – 3 times daily. If using an alcohol tincture I like 1-2 drops per lb BW, twice daily with food. Jean Hofve uses up to 200 mg per 10 lbs BW for acute illness involving the liver.

Also Consider: Depending on the condition and individual (dog or human) consider licorice, dandelion, Oregon grape, burdock, yellow dock or turmeric.

Resources/Further Reading (veterinary):

Manual of Natural Veterinary Medicine, Susan Wynn DVM and Steve Marsden DVM

Veterinary Herbal Medicine, Susan Wynn DVM and Barbara Fougeres

Herbs for Pets, MaryL. Wulff-Tilford and Gregory L. Tilford

Botanical Medicines; the Desk Reference for Herbal Supplements; McKenna, Jones, Hughes, Humphrey

The Natural Health Bible for Dogs and Cats, Shawn Messonnier DVM

article Jean Hofve, DVM:


9 thoughts on “Silybum Marianum – Milk Thistle

  1. Curious…does “under abnormal stress” include Microvascular Dysplasia? My dog has that and I’ve been giving milk thistle to her since her diagnosis, but on and off like you recommend above.

    • Absolutely it does, Heidi – in most of the MVD cases I’ve worked on, we use MT for life, but with rests…SAMe for life, and a careful diet – “liver-friendly” in that fish is usually the main protein, I like one week a month vegetarian, and chlorella is a very useful support, as is lipoic acid. Just a few ideas, I always emphasize the importance of personalizing protocols – how a old is the dog, are there other conditions, and so on. 🙂

  2. This has been a very informative and helpful article on nutrition. Our life for 11 years evolved around marketing a premium dry dog food and never really considered the alternatives. There is a lot of “food for thought” here. Thank you so much.

  3. Hi, I have a 33kg Alaskan Malamute who is 11.5yrs old. She has had chronic pancreatitis all her life and was diagnosed at the start of the year with chronic kidney failure. She has taken NSAID’s for the past 5 yrs for a painful spinal condition.

    I have recently started giving her milk thistle powder but only a level teaspoon mixed in with her meals at night. I get confused with doing the math on how much I need to give her…is it possible to let me know how many teaspoons I should be giving her daily (approximately) please?

    Also, I have been giving her a level teaspoon of Yucca Root powder in her meals also to help the inflammation of her spinal injury, so I can eventually get her off the Rimadyl (NSAID) and prevent further kidney damage….however, I’ve recently read in a few places that Yucca root shouldn’t be given to those with kidney disease. I’ve asked a few of those sites to please explain why but none have responded. Do you have any information on this at all please?

    It would be most appreciated as I hate the thought of giving her something that could make her worse off even though it appeared to help with the inflammation and pain.

    Regards, Michele.

  4. When I took my 2 year old male Chinese Crested in for neutering, I was told his liver levels were high…over 200, which is 2x the average. The breeder checked with her Vet and said it was normal for this breed to have a higher liver level. I swithched their food from Eukanuba to Acana, Wild Prairie. Three months later, I took my 5 year old female in for spaying. I was told her liver level was also over 200. The Vet wanted to put her on meds for her liver, I did not agree with him. Both of my dogs are very healthy, no signs of any problem. I’m concerned with the liver levels and have the breeder telling me one thing, the Vet another. Should I begin Milk Thistle as a supplement?

  5. I am not a VET. I am a concerned owner. From what i understand the Pet grade supplements arent Regulated anywhere near the Human Grade supplements. As in Dog food compared to human food. I have ZERO worry of giving my friend 1/3 cap of 80% Standardized silymarin per day. 5 days on 2 days off. for 6 wks. then periodically { BEWARE of baking Soda,powder Carpet Freshner, & Lawn Fertilizers, & Manure ! } This is for a 13lb female pom, that is on Prednisone For what they say is autoimmune disease. Her platelet ct was at 13K. per ML 1 week ago. Today 3-6-12 its at 256K per Ml. yet the Vet wants to leave her on Prednisone For Months….. I let her know, AINT going to happen ! also she told us that the Drug Azathioprine is causing liver damage & to stop it. { how can she know if shes on Prednisone also?} & to Come get another drug Cyclosporine…..I can see after all the 10s of 1000s & millions of posts, why Dog owners are confused. The hamster wheel is apparently the norm. I read many posts, that showed the vets had done the same to many owners……. many that were on long term drug THERAPY they call it, lived a life that according to the owners, wasnt worthliving. Proceed with Caution. the same drugs that can save your life in emergency, Can Kill. Yet before they do, cause so many ailments you dont have a clue where your at…….. Best regards be patient, Talk to who you can, Beware of theyre motivation. Milkthistle is giving to MANY the world over for supporting a Healthy liver function.

  6. I have a 31/2 yr. old Yorkie (Neo) that gets a weekly allergy shot and takes 1/2 of a Temeril-P tablet twice to three times a week. He and my other Yorkie both take Trifexis once a month. I discussed with their vet about starting Neo on milk thistle. He thought it a good idea, but did not give any dosing instructions. I would also like to give my other Yorkie milk thistle whenever he gets the monthly flea and hw treatment. Neo is 10 pounds and Conner is 15 pounds.

  7. My dog has been on loumustine (sp) for her cancer. She is now on Denamarin (sp) for her liver because of the chemo. Is it ok to work milk thistle in with her meds?

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