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

Dog Cancer and Antioxidants…Time to Clear Up Confusion!

Updated: December 18th, 2018

Hi everyone,

The use of “antioxidants” is a charged topic in cancer care these days.  The holistic set tends to be “pro”, while the western vets and oncologists tend to be “anti”.  Let’s take a look from my favorite viewpoint…Full Spectrum care ( where we try to avoid biases that exclude useful things but gear evaluations towards real-life effects).

Here’s the problem: the use of the term “antioxidants” is totally muddying up our thought process in trying to give sound advice!  We need to totally eliminate this word from our discussion!! Yes, sounds a little weird.  So let me explain what I mean.

First, let’s widen back. What is an “antioxidant” anyway? Usually, people talk about the ability of a substance to help decrease the free radical activity in the body.  A free radical is what you get when you are consuming oxygen in body processes over time.

Free radicals tend to be harmful to living cells. There are many different types of free radicals but many contain  “used up” oxygen that was used for normal living processes or are the result of the reactions that use oxygen.  So that’s the oxygen connection to “antioxidant”.

The problem is this: most of the substances or vitamins that are classified as “antioxidants” have never even been shown to do that in a real-life body! (Check it out here)  And to top that off, many of the so-called antioxidants have “pro-oxidant” activity.  This means they are capable of increasing free radical effects.

Don’t go away mad, because there is more:  in many strategies in combating cancer, we want free radical generation.  Yes, we want free radical production, that was not a typo.  For example, we want free radicals to increase in cancer cells, so they die.  And we want to leave body cells unharmed in the process.  This is the theoretical basis supporting the use of radiation and some chemo treatments.

Some of the items in past or future postings on dogcancerblog.com attack cancer cells in this way while leaving normal body cells unscathed.

Now I hope you are starting to see what I am talking about. It gets thicker though, so hang on, please.

There is major confusion surrounding cancer prevention, compared to cancer treatment.  Free radicals are one of the things that can damage DNA and contribute to cancer development.  That is one process, and the use of substances that block this process can help decrease the odds of getting cancer.  However, the use of the same substance at the same dose may not decrease cancer after it has developed (this is very frequently the case)!

For more helpful tools and information, get a copy of the Dog Cancer Survival Guide

So there are two entirely different instances…before a dog gets cancer, and once it has developed the disease.  Prevention and treatment….totally different!

People tend to use the word “antioxidants” as if they are the all same.  So “antioxidants”, all grouped together,  are “good” or “bad” in veterinary cancer care.  As if each substance, vitamin or therapy that has an antioxidant effect is the same as other, with the same effects.  Folks, this just wrong.

Each of the vitamins, enzymes, drugs, therapies and so on that are capable of quenching free radicals, or contributing to decreases in free radicals, is completely different.  They have different effects! Grouping them into a single functional category is a mistake.  The premise is flawed.

Talking about “antioxidants” and cancer care is like talking about “people” and the upcoming election.  Yes, we all have, oh, say, a beating heart.  True.  That is a similarity.  But can we make a statement that we will all operate the same at election time?  Of course not.  Just as you cannot group people with beating hearts in a single functional category just because they have a similarity, you cannot group antioxidants in a single functional category.

To learn more about diet for dog’s with cancer, get a copy of the Dog Cancer Diet

Each is unique.

And to impress the point further, the use of a given substance that has an antioxidant effect may have good or bad interactions with other treatments.  The antioxidant effect may help or hinder in the context of what else is going on.

And what about all the other effects of the given substance? It will do a lot more than affect free radicals!

So, I believe we have been white-washing this entire area, perhaps out of a lack of information, or out of fear that we might worsen our already junky success rates with conventional care of malignant cancer.  Or maybe we have just been a little lazy, hard to say.

I will address specifics in this topic in future blogs, but I wanted to get this idea out there first.  This is our launching pad.

Best to all,

Dr Dressler


Discover the Full Spectrum Approach to Dog Cancer

Leave a Comment

  1. Agata on April 27, 2013 at 2:01 am

    I wonder what is your opinion on microchips. My Labrador suffered from skin mast cell tumours for 9 years. He developed the first tumour 6 months after being microchiped and had countless surgeries to remove the tumours. Eventually it spread internally and killed him. I had always had a feeling that the reaction was to the microchip being a foreign material in the body. Non of the vets could give me a definite answer, they have never heard of it, but this doesn’t mean that it can cause cancer especially of this type which is a mast cell over- reaction. What is your opinion? Just in case I did not microchiped my new dog but it’s not easy to register a dog without a microchip.

    • Dr. Demian Dressler on May 9, 2013 at 3:37 pm

      I Agata,
      I have not seen a microchip induced cancer in dogs before…
      Dr D

  2. Dr. Dressler on December 18, 2008 at 4:42 pm

    Yes. Resveratrol is so cool except we don’t know what the toxic agent is in cases of grape toxicity…I would be quite excited about it otherwise.

  3. Lilly F on December 17, 2008 at 3:28 pm

    Dr. Dressler,

    So in light of what you say about using grapeseed extract cautiously. Would you also use resveratrol the same way since it is also derived from grapes?


  4. Dr. Dressler on October 11, 2008 at 3:39 pm


    I was trying to make the point that each antioxidant needed to be considered, and all its effects, in the context of a given dog within a specific treatment plan. I was not actually trying to make a harm versus good statement…

    Just a quick note on the grapeseed extract. Yes, good stuff upon initial exam, but I cannot recommend them to everyone, as a precaution. Do a Google search on grape and raisin toxicity in dogs and you will see why. Since we don’t know what the culprit is in the grape, and the rare death does occur, I have to err on the side of safety (even though it could be that the vast majority of dogs would be fine with grapeseed extract, we just do not know)

  5. Ellen Miles on October 9, 2008 at 2:15 pm

    Hi Dr. Dressler,

    I just found your blog. Interesting notes. I agree, some antioxidants and (many forms of minerals) cause more harm than good. It’s recently been found that most the minerals in most supplements actually crystalize in the small intesting, throw off lots o’ FR’s, using any antioxidant in site and causing more harm than good. Studies conducted by Alexander Rabovsky, PhD and Jeremy Ivie conducted initial research with Andrei Komarow, MD., PhD of George Washington U and Garry Buettner, PhD, professor of free radical science at the University of Iowa tested and verified the research.

    A while back, I was searching for the effect of grapeseed extract on cancer. Among other things, its a strong antioxidant, (a flavanoid). Somewhere, tho I can’t find it again, I saw where in some types of cancers, it encapsulated the cells and destroyed them… I believe it’s also been effective in some forms of colon cancer.

    I give my dog grapeseed extract for her allergies and after about 8 months, she no longer has allergic reactions (to environment and cats). Still feed her a grain free diet, but that’s not jjust because of allergies. She’s doing great.

    Look forward to hearing more about ca and dogs. Haven’t checked your whole blog but have you done research on the link between common chemicals and ca?


  6. Lori Michaelson on October 4, 2008 at 11:10 am

    Off course I meant to say antioxidants not antibiotics!!! LOL


  7. Lori Michaelson on October 3, 2008 at 11:37 am

    I just wanted to make a general comment about antibiotics which, I believe, goes along with what you said about antibiotics.

    For the longest time The Food and Drug Administration said that Vitamin E and Vitamin C said that they were the most potent antibiotics to prevent cancer, to directly help this or that condition or this or that organ etc. And then it was just last year where they had to admit that "they" really had no proof or basis for suggesting what they did 30 or 40 years ago.

    You know how folks are always saying "They suggest this" or They suggest that." And whom "THEY" are is really an enigma.

    Okay, now what I really wanted to say. I’m sure that there are many, many people who take Vitamin E daily (like myself and my husband) but when you purchase it over the counter from Costco or Wal-Mart, etc…. you are really only getting the "synthetic form" of it and not the REAL or most natural Vitamin E.

    Not that there is’nt ANY benefits to buying the over the counter type but if you want the real thing — order it in it’s true form which is Alpha Tocopherol. This natural form is more active and better absorbed. 🙂


  8. Dr. Dressler on October 1, 2008 at 11:39 pm

    sorry to hear the chemo is making your girl feel junky. You will find split camps on when to start melatonin. Honestly, my feeling is to go ahead and give it when you want it (like now). I am sure I will create an uproar but there ya go. The statistics post amputation with osteosarc are garbage. So we have little to lose and a lot to gain.
    No harm in starting the Transer Factor before K-9 Immunity, but they are designed to be used together. There is a wee immune stimulating affect likely with TF but this effect minimal in my opinion by itself.
    It is difficult to overdo the omega 3 supplements. Just start slowly and work your way up (see the blog on omega fatty acids).

  9. Lilly F on October 1, 2008 at 1:19 pm

    Regarding the antioxidant vitamin C–oral versus intravenous.

    Candy has Mycosis Fungoides, or Cutaneous T cell lymphoma. for which she received some IV vitramin C (2 rounds–about 3-4 days each time) since June It did wonders for her coat and skin. However, I have stopped the oral vitamin C because what I read says that in low doses it is taken up by the cancer cells, promoting cancer. once once has cancer . As an IV, it supposedly kills the cancer (orthomolecxular.org site) . Do you agree with this or is it the answer that nobody really knows yet?


  10. Lilly F on October 1, 2008 at 11:19 am

    My dog has Cutaneous T cell lymphoma and some of the information I have read is different for lymphoma than it is for lets say an organ cancer. I have read for example that immune stimulating supplements should not be given–isn’t that just about everything out there–since the immune system is supposed to fight disease–why WOULDN’T you stimulate it?

    Also, I read that melatonin should not be used with “lymphoproliferative” cancer. Again,. My Candy is taking melatonin for Atypical Cushings so maybe I need to consider the lesser of the evils and stop it.

    I don’t know if the advice I read for cancer applies to lymphoma. I hope that I am not doing my poor dog in with my ignorance 🙁

    I am giving her curcumin, l arginine, Reconciling tablets, fish oil, selenium , artemisinin, Avemar among other things but don’t know if these might be contraindicated. Is this way too much information–I have a million questions.
    This website is my new best pal!

  11. Dawn on October 1, 2008 at 3:11 am

    Hello! I have ordered K9 Immunity. I know I had talked to you about my thoughts on waiting 2 days after chemo to start her melatonin again ..but Gabby had her chemo yesterday and we were up all night with her. So I am concerned and wanted to verify that it is safe to give her her melatonin tonight instead of tomorrow. I am concerned on the toll the chemo is taking on her her body.
    Also, I already recieved the K9 transfer factor so should I wait for the K9 Immunity to use? I also ordered the K9 omega although her food has .7% of Omega 3 nd 1.5% of Omega 6. Is the K9 Omega still safe to adminster?
    Thanks again!
    -Dawn & Gabby

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