Milk Thistle for Dogs


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I had been struggling for the longest time to eradicate a bristly plant from my garden, without much in the way of success. I don’t use herbicides, since I worry about having my dogs come into contact with them, so I just kept on pulling vigorously, and also tried a solution of salt water in an attempt to get rid of the pesky thing.

The salt water solution, touted on various Internet sites as being a virtually foolproof way of getting rid of almost any weed, failed to work. The leaves turned brownish and crinkly for a while, but then the plant came back stronger than ever. Finally (and yes, you can call me crazy), I started thinking that maybe something that tenacious had a right to live – but what was it?

A bit of vigorous Googling revealed the unwanted plant to be milk thistle. It looks like this:

It’s pretty, isn’t it, with its jade green foliage with pretty purple blossoms? I’d imagine that in some part of the world, this invasive plant is actually considered a desirable part of the garden, but where I live, it just grows like crazy and chokes out other plants. Being of a curious nature, though, I wondered if milk thistle actually had any use, and my research has revealed that it does! So what is milk thistle good for? Well, in dogs and in humans, it’s good for quite a lot. Before we get into the benefits, though, let’s talk a bit about the plant itself.

What is Milk Thistle?

To look at this plant, and to compare it with the soft-petaled white daisies with the brilliant yellow centers that you see growing in meadows and at roadside, you wouldn’t think that the two plants have anything to do with one another, but the fact is, they’re closely related. Maybe that’s why they’re often found growing in close proximity to one another.

Milke thistle has its origins in the Mediterranean, where it was often used as a medicinal plant. Most likely it found its way to North America in the way that several other plant species did – accidentally, by way of seeds that somehow found their way onto trading ships. Once established, the plant becomes very hardy, since there are no diseases known to affect it, and it’s virtually pest-proof.

The plant, which is also known as “holy thistle” or “Mary thistle,” is highly adaptable, requiring only well-drained soil in order to flourish. In fact, unless it is vigorously controlled, it can become very invasive (as its constant presence in my garden would indicate). This is, of course, a huge benefit to those who actually cultivate the plant in order to harvest it for use in herbal medicines and supplements.

Benefits of Milk Thistle for Dogs and Humans

Much of the time, what is good for humans is not good for dogs. For more on this topic, see my post, Your Dog is Not a Human, So Don’t Feed Him Like One. Sometimes, though, what is good for you can be very good for your dog, and milk thistle is one of those things that can benefit your dog in a significant way.

The beneficial ingredient in milk thistle is silymarin, and it’s been proven to be helpful in enhancing liver function. It’s also believed to have the ability of lowering “bad” cholesterol, and to be effective in managing type 2 diabetes.

The benefits of milk thistle are the same for dogs as they are for humans.

Milk Thistle

10 Benefits of Milk Thistle for Dogs and Humans

Keep in mind that milk thistle is not a cure-all. As an example, if your dog has liver cancer, you could give him milk thistle supplements until the cows come home, and it won’t help – I’m sorry to have to tell you that liver cancer is almost always a death sentence for dogs.

That said, though, mild to moderate liver issues may respond well to milk thistleSo might other health conditions. Here are the 10 benefits of milk thistle for both dogs and humans.

1. Healthier Liver

The key here is silymarin, the active ingredient contained in the milk thistle plant. Studies have shown that it acts as an antioxidant, improving liver health. As a caveat, though, I have to tell you that milk thistle is not recommended by most medical practitioners as the primary treatment for liver disease – rather, it’s a complementary treatment, to be used in conjunction with conventional medicines. The worst case scenario is that using milk thistle will cause no harm, and it might do some good!

2. Lower Cholesterol Levels

If you’re of a certain age, your doctor may want you to have blood work done regularly to determine whether your cholesterol level is too high. Milk thistle has been tested in several studies, and the results seem to indicate that people who regularly use a milk thistle supplement have lower cholesterol levels than those who do not. Again, this is a “might not necessarily help, but won’t hurt” scenario, and it’s the same for your dog as it is for you.

3. Better Skin Health

Milk thistle oil is used in many commercially prepared body lotions, and has been found to reduce skin inflammation. It may also have anti-aging effects on the skin, although the jury is still out on that. If your dog has itchy, dry skin, using an unscented lotion that contains milk thistle oil could ease the condition.

4. Weight Loss

Is your dog “chunking up”? In 2016, researchers discovered that silymarin, the active ingredient in milk thistle, actually caused mice to lose weight – while they were on a diet that was designed to facilitate weight gain! More research is needed in order to determine if this will translate over to humans and dogs, but the results do seem promising.

5. Better Diabetes Management

Milk thistle is also believed to reduce insulin resistance in type 2 diabetics.

6. Reduction in Asthma Symptoms

Silymarin has been found to reduce inflammation in the airways of mice. As is usually the case, more research will have to be done in order to determine whether humans and dogs will benefit in a similar fashion, but it does look promising.

7. Stronger Bones

Bone loss can often be due to a decrease in estrogen, and this can be a problem in both humans and dogs. Milk thistle is believed to help prevent bone loss due to estrogen deficiency. It’s worth noting, though, that it’s not known whether milk thistle will work as effectively against bone loss that is due to reasons other than estrogen deficiency.

8. May Slow Some Cancers

Milk thistle may help to slow the progress of some types of cancer. A study in 2015 revealed that the growth of cancer cells was slowed in some patients who had colorectal cancer. Keep in mind, though, that this does not mean that milk thistle will necessarily work to retard cell growth in other types of cancer, and does not necessarily mean that the outcome will be the same for dogs as it is for humans.

9. Better Immune Response

Studies suggest that milk thistle can improve the function of the human immune system. The research is in its infancy, though, and more will have to be done before we can conclude decisively that milk thistle boosts the immune system in humans, and in dogs.

10. Better Brain Power

Milk thistle is believed to improve cognitive function in humans. However, more research is needed, and we still don’t know if this will translate over to our canine friends. Given that milk thistle seems to work in the same fashion on both humans and dogs, though, if your best buddy seems to be a little less focused than he once was, milk thistle will do no harm, and might do some good.

So now you know the potential benefits of milk thistle for dogs, and for humans as well. Let’s move on to learning how to administer this amazing supplement.

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Administering Milk Thistle for Dogs

You can buy milk thistle supplements for humans in any health food store. There is no standard dosage for humans, so if you’re planning on taking milk thistle, you’d be well advised to read the packaging carefully.

For dogs, the dosage is based on the silymarin content – usually around 80% in any given supplement. The silymarin content can vary widely, though – as little as 50 milligrams, and as much as 500 milligrams.

So, how much milk thistle for dogs? Well, for dogs with advanced liver disease (and again, I caution you not to hold out a lot of hope here), the dosage can be as high as 200 milligrams per ten pounds of the dog’s body weight. I urge you, though, to consult with your veterinarian before taking such extreme measures. For most dogs, anywhere between 75 milligrams and 100 milligrams is enough. Keep in mind that too high a dosage can lead to gastric distress.

It’s usually better to administer the milk thistle supplement in small doses over the course of the day rather than all at once.

You can find milk thistle supplements in capsule form or as a liquid extract. When purchasing the liquid form, though, read the label carefully – many liquid milk thistle supplements also contain alcohol, and alcohol in even small doses is very bad for dogs.

Now, if all that you’ve read so far has led you to think that milk thistle for dogs is a very good idea, I think you’re probably right. There seems to be little to criticize and much to praise when it comes to the benefits of milk thistle for dogs, and for humans as well. However, I’d be remiss if I didn’t tell you that there can be a down side.

Risks and Side Effects of Milk Thistle for Dogs

Milk thistle is considered to be a supplement, not a drug. Accordingly, the FDA (Food and Drug Administration) in the United States does not regulate milk thistle.

The first thing that you need to know about milk thistle for dogs is that it could interact with other medications. If your dog has liver disease, you should definitely consult your veterinarian before deciding to administer milk thistle, in order to determine whether it will react badly with other drugs that your dog is taking for his condition.

The second thing you need to know is that not all veterinarians are going to enthusiastically embrace the idea of using a natural supplement like milk thistle for dogs. If you’re considering this supplement, I would highly recommend consulting a holistic veterinarian.

What is a Holistic Veterinarian?

Holistic veterinarians are increasing in popularity, but the fact is, holistic veterinary medicine isn’t a new concept. Holistic medicine, for both humans and dogs, simply means that the condition is treated as part of the whole body, not as a condition in and of itself. A holistic vet will consider everything that is going on with your dog, not just the physical symptoms – he or she will also consider your dog’s lifestyle, and his emotional well-being. Much of the time, medication will be administered as an adjunct to your dog’s lifestyle and mental health as opposed to simply being given to treat physical symptoms.

It’s also important to know what a holistic veterinarian isn’t. Often, when we think of holistic medicine, we think of things like acupuncture or chiropractic treatments. Granted, some of these methods may be employed when it comes to holistic medicine, but they’re not the whole picture. Holistic medicine can also include contemporary medical procedures and nutritional approaches.

Also, if you expect a “holistic veterinarian” to approach your dog using crystals and mind-melding and other “new age” techniques, you’re going to be very disappointed. It’s more likely to involve combined disciplines, one of which will definitely be modern medicine. When you and your dog visit a holistic vet, you can expect that the vet will conduct a traditional examination, in which he or she will ask you for stool samples, check your dog’s ears, eyes, teeth and gums, and give your dog’s body a “once over” to check for any problematic lumps or issues with the hips and spine.

What you will not experience with a holistic vet, generally speaking, is the traditional examining table – the vet is more likely to get down on the floor to examine your dog. You will also likely experience fewer questions about your dog’s physical health, and more about his emotional health. Overall wellness is the focus of the holistic vet, and that means attention to everything that is going on with your dog – not just his physical issues.

A lot of the time, people turn to a holistic veterinarian as a last resort, when other methods of ensuring their dog’s health have failed. This is unfortunate, since a lot of the time, dogs who have been treated holistically enjoy a better quality of life, and a longer life, than those who have been treated conventionally with medications and surgeries.

Understand, please, that I am not suggesting that your dog shouldn’t receive traditional medications, or have surgery when it is needed. However, I do not believe that it’s always the best course of action. Veterinary treatment, from my perspective, should rely as little as possible on medications and surgeries. This is the case for humans as well as for dogs. Good nutrition, exercise, lots of love and a healthy lifestyle should always be the first course of action.

And supplements? Well, talk to your holistic veterinarian. Supplements like milk thistle for dogs can be a good way to prevent illness, and sometimes to treat an illness that has already developed.

Keep in mind, though, that there are no special requirements for a doctor of veterinary medicine (DVM) to represent himself or herself as a “holistic veterinarian.” It’s an approach, not an accreditation. It may be that your “traditional” vet is every bit as competent, if not more so, than the holistic practitioner you’re considering.

Now, back to milk thistle for dogs.

Milk Thistle Can Undo Damage – Sometimes

As we’ve already discussed, milk thistle contains silymarin. This ingredient works to displace toxins that attach to the liver, and by doing so allows the liver to regenerate more rapidly. It works as an antioxidant, getting rid of free radicals and encouraging the liver to generate new cells.

In this way, silymarin reduces the damage cause by:

  • Chronic liver diseases like hepatitis
  • Pancreatitis
  • Leptospirosis
  • Skin problems due to liver disease.
  • Fatty liver
  • Cushing’s disease

One thing, though, that milk thistle will not help, is cirrhosis of the liver. And yes, dogs can get it. You probably think of cirrhosis as being something that humans get if they drink too much, and you wonder, if dogs don’t drink, how can they get cirrhosis?

The fact is, cirrhosis can be caused by toxins other than alcohol. And yes, dogs can get it. Cirrhosis is an “end stage” disease, meaning that there is nothing that can be done to correct it. It’s a death sentence. So if anyone tries to sell you milk thistle, or any other supplement, telling you that it will cure your dog’s cirrhosis, just walk away and make arrangements to take your dog gently and lovingly out of this life. I’m sorry if that sounds harsh, but there is no hope when it comes to cirrhosis.


Milk thistle is a powerful antioxidant, not just for the liver. It can also boost the immune system in dogs that are recovering from chemotherapy or have had a serious worm infestation. It can also help dogs that are recovering from parvo, but I have to tell you here, if you think for one minute that milk thistle is going to prevent canine parvovirus, then you need to pull back, regroup, and grow a brain!

Nothing. Nothing. NOTHING prevents parvo except a vaccination. If you have behaved like an unspeakable moron and not gotten your dog his parvo vaccination, then milk thistle might help with his recovery – if he lives. Chances are he won’t.

Please, by all that is holy, get your dog his parvo vaccination.

What About Safety?

We’ve talked a lot about the benefits of milk thistle, but you’re wondering, “Can I give my dog milk thistle the same as I would for humans?”

The answer, generally, is YES. You can. It’s safe.

However, most veterinarians recommend that you give your dog milk thistle on an empty stomach, and proceed with caution. Use a low dosage to start with, and watch your dog carefully for signs of diarrhea, gas, or an upset stomach.

Another thing to keep in mind is that milk thistle can be a bit of a paradox – it can be very good for dogs that have liver problems, but in dogs that have a healthy liver to begin with milk thistle can actually suppress liver function!

Milk thistle should also not be used in conjunction with Ketoconazole, Phenobarbital, Midazolam, Glucocorticoids and calcium channel blockers. It should also not be used for pregnant dogs or humans.

In short, use milk thistle only as needed, only when needed, and only under the supervision of your veterinarian.

Milk Thistle or Denamarin?

There’s another supplement out there, Denamarin – it’s very similar to milk thistle, and in fact contains a similar active ingredient – silybin – which is also extracted from milk thistle.

This supplement is represented as causing few or no side effects, and the research shows that dogs do very well on Denamarin. Some holistic vets don’t like it, though.

Why is that?

Well, holistic vets prefer, generally, to use the whole plant, not just an extract or two, and they point out that dogs that do well on Denamarin usually do even better when they’re switched over to milk thistle.

I’m not an expert, but it seems to me that if I’m going to give something to my dogs, I’d prefer to give them everything that might benefit them, not just the extracts. I could be wrong, though, so don’t take my opinion as the gospel truth.

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The Final Word – Is Milk Thistle Good for Dogs?

I think it is. Everything I’ve read after finding that little plant in my garden has led me to believe that maybe I shouldn’t pull it out – I should let it flourish. This funny-looking weed might actually have properties that can help to keep me – and my dogs – healthy. At the very least, it won’t do any harm, and the research seems to suggest that it might do a lot of good.