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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Could Killing “Good” Bacteria Increase GI Cancer Risk?

Updated: February 17th, 2021


Probiotics are linked to all sorts of necessary bodily functions. But do they really help to prevent cancer?

Could destroying the normal bacteria in your dog’s body be a risk factor for cancer down the road?

This may sound very far-fetched.  However, in the spirit of avoiding condemnation before an investigation, read on!

Do Probiotics Prevent Cancer?

It turns out that the so-called “healthy” bacteria in the body may provide cancer protection.

Good bacteria, also called probiotics, help digest food, release enzymes, and ensure that nutrition is properly absorbed. They also can have anti-tumor effects through several different mechanisms. They aid the body in keeping balance or homeostasis.

They help the immune system work properly, too. A healthy probiotic population might lower the risk for tumors of the digestive tract, liver, and bladder.

So what happens if these good bacteria are destroyed with antibiotics? They can be replaced with “unhealthy” bacteria. Does it follow that there is a cancer risk?

Where Probiotics Live in the Body

Let’s first look at the natural bacteria found in bodies.  These live mainly in the GI tract but are also located on the skin and in body cavities.  Healthy intestinal bacteria vary between species but can include bacteria like some strains of lactobacillus, bifidobacteria, strep, and others.

These bacteria are beneficial as they help block disease-causing microbes, help stimulate immunity, and help provide the body with vitamins.

However, what happens when these bacteria are destroyed or never received in the first place?

What Happens When Good Bacteria Are Gone

The frequent result is that the intestine is colonized with bacteria that are not especially healthy, such as some strains of clostridia and Bacteroides.  These do not provide the benefits of healthy bacteria, and there is some research that they may produce toxic waste products that create inflammation and precancerous changes in the intestine of lab animals and humans.

Additionally, helicobacter is a risk factor for stomach inflammation and pre-cancerous changes, as opposed to the intestine.  This is another example of an “unhealthy’ bacteria.

Although there is not a direct cause and effect yet established in pets or people for many of these changes, I believe we will be seeing much more data on this over the next decade. The microbiome is a hot topic for researchers.

Get more advice on diet and soooo much else in this book. A must-read even if your dog doesn’t have cancer!

Ask Your Veterinarian for a Probiotic After Antibiotic Use

If your dog has been on antibiotics for 3-7 days or more, I recommend you discuss probiotics with your vet. A couple of weeks use of a high-quality probiotic supplement can replenish the gut with the good stuff.

Make sure this healthy bacteria supplement is protected from the stomach acid and enzymes so it can reach the lower part of the intestine without being destroyed in the stomach.  There are different quality probiotics, and you want to get one that will make it to its favorite home.

I feel that lower potency sources such as organic yogurt may not be entirely adequate, especially if your dog is really empty of a good population.

Finally, you may provide the fuel for these bacteria, which are called prebiotics.  One common one is inulin.

While a prescription probiotic is needed for acute conditions, ongoing support can be found in an over-the-counter supplement, as well as fermented foods, of course. I personally like the pre- and probiotics support included in the daily apoptogen formula I created called EverPup.


Dr D

Further Reading & References

Probiotics: What You Need To Know | NCCIH (

The Microbiome – Science Friday

Kumar M, Kumar A, Nagpal R, et al. Cancer-preventing attributes of probiotics: an updateInt J Food Sci Nutr. 2010;61(5):473-496. doi:10.3109/09637480903455971

Yu AQ, Li L. The Potential Role of Probiotics in Cancer Prevention and Treatment. Nutr Cancer. 2016;68(4):535-544. doi:10.1080/01635581.2016.1158300

Śliżewska K, Markowiak-Kopeć P, Śliżewska W. The Role of Probiotics in Cancer PreventionCancers. 2021; 13(1):20.

Leave a Comment

  1. Ed Capps on November 15, 2012 at 4:03 am

    Dr D,

    I have been reading about mushrooms being very beneficial for gut flora, and some such as Reishi mushrooms even show some evidence for bringing about apoptosis. I am going to start taking them myself, and wondered if they are safe for dogs.

    Thank you

    • Dr. Demian Dressler on November 27, 2012 at 12:00 pm

      Dear Ed,
      this is discussed at length in the Guide, which is a good read for anyone interested in topics like this. I would suggest a veterinary supplement for beta glucans like k-9 immunity or similar.
      The other thing you could do is check out everpup, which has some beta glucans and a whole slew of other beneficial ingredients for cellular protection.
      Dr D

  2. steve on June 6, 2012 at 12:50 pm

    dear dr. dressler, My dog max, a boston terrior, died suddenly of hemangiosarcoma in his heart. He was 11years old. He had chronic glaucoma and was blindin that eye but he was not in any pain which was controled by the eye drops. His eye pressure was normal. How ever I was wondering what could have caused this cancer that ended his life. I loved him more than anyone in my life and still am in some shock about his death which was back in october. thanks

  3. Garry Sheen on June 6, 2012 at 4:20 am

    It’s really great to hear that Kayla is doing so well:) Our Logan was diagnosed with TCC at the beginning of May. Unfortunately, the tumour isn’t operable, but he is receiving chemo and the supps he is on broadly reflect Kayla’s (we’re hoping for him to be on Apocaps soon). We’re having great problems getting him to eat (I give each of the supps with a little pork liver treat just before we attempt a meal!) even though it’s almost 3 weeks since his last chemo session.
    Apart from wishing you and Kayla all the very best, Margaret, I’d also be interested in hearing what Dr D has to say re. EverPup for dogs with cancer.
    Warm regards
    Garry (UK)

  4. Margaret (& Kayla) on June 1, 2012 at 10:30 pm

    Hi Dr. Dressler,

    My dog, Kayla, (and I) are dealing with a recent diagnosis of TCC. She has had a successful surgery to remove cancerous tissue from her bladder (4 week post-surgery ultrasound this week looks great and there is thus far no lymph node involvement). She is a 23 lb. 9-year old schipperke/papillion/border collie mix (best guess of our vet, as I adopted her at 6 months of age from a shelter). She has been on your dog cancer diet for 6 weeks with K-9 Immunity, Transfer Factor, digestive enzymes, Apocaps (1/2 dose), and Metacam. Daily Cipro (morning) was added this week along with a high quality probiotic (evening), and I started her on modified citrus pectin this week as well. She is eating, drinking, peeing(!), playing, and sleeping very well (I live in Fairbanks, Alaska, and have created a dark den for her to sleep in despite our current midnight sun). My question is, will she benefit from the addition of EverPup, or is it contraindicated with her current cancer and related treatment(s)?

    Kind regards,
    Margaret & Kayla

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