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

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Vitamin D and Dog Cancer

Dog lovers will do anything they can to help their dog with a cancer.  And you should! This can be one of the hardest times anyone will face.

Many times the effort helps, and other times it may not.

This, of course, is not due to any ill intention on the part of the dog’s human.  Rather, it is simply because there is inadequate use able information out there.

Take, for example, the use of vitamin D supplements for dogs with cancer.

Well yes, sure, cancer in the test tube will undergo apoptosis (normal, healthy end of life cycle) when exposed to the body’s active form of vitamin D.  Here is a publication to look at.

And yes, some cancer cells have little empty “locks” on the outside of them (receptors) that fit the vitamin D “key”.  When the key fits the lock (vitamin D binds the receptor on the outside of the cancer cell), the cancer cell commits suicide.  Take a look here.

So, doesn’t it make sense that if a dog were to get cancer, giving vitamin D would be a smart move??

Well, not really, not quite.

First,  remember we always have to ask whether the stuff in the pill gets all the way to the cancer in the body.  We give our dog a pill, and the active ingredients have to be taken into the blood by getting through the wall of the intestine, making it past the liver, escaping excretion into the urine, getting back out of the blood, and bathing the cancer cells in the tumor.

That’s a pretty long trip.

Turns out that it is hard to get the vitamin D all the way to the cancer cells. Blood levels of the most active form of vitamin D (calcitriol), are mainly produced by exposure to direct sunlight on the skin, not by taking it by mouth to get high blood levels.  Look for yourself.

Of course, if you take enough, you can get high blood levels that can help with cancers in the body.  The problem is that you also may get dangerously high blood calcium levels.  Active vitamin D boosts blood calcium levels.  When you get excessively high calcium levels, bad things start to happen (kidney injury, heart problems, and more).

So we have a quandary.

What to do?

Well, big pharma is trying to make drugs like active vitamin D for cancer, but without the high blood calcium bit. Here is some info about that. The problem is that they are not available yet.

So can we do anything?

Yes, two things. First, get your dog into the sun, with a few exceptions.  Sunlight has a dramatic effect on active vitamin D levels in the blood. We are talking about direct sunshine a couple of times a week, about 10-20 minutes each time.

A word of caution: do not overheat your dog!! Long hair, short muzzles, breathing problems, obesity, and other issues can increase heat stroke chances. Check with your vet.

Another word of caution:  squamous cell carcinoma, as well as hemangiosarcoma of the skin, have increased risk with sun in dogs.  Don’t do a lot of sun if your dog has these cancers. Get a full spectrum lamp for seasonal affective disorder in people.

By the way, do not worry if your dog has melanoma.  This cancer has not been shown to have a link with sun in dogs.

The second thing you can do is make sure your dog is getting maintenance vitamin D levels. My  personal opinion supports a balanced multivitamin for dogs with cancer.  It has been shown that vitamin D deficiency does bad things like increase certain  cancers, like colon cancer in mice.  Read about it here.

So get your dog some sun and his or her normal, dietary level of vitamin D. Don’t bother with the high doses for dogs with cancer.


Dr D

About the Author: Demian Dressler, DVM

Dr. Demian Dressler, DVM is known as the "dog cancer vet" and is author of The Dog Cancer Survival Guide: Full Spectrum Treatments to Optimize Your Dog's Life Quality and Longevity.

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  • Ollie

    My jack russell has bladder cancer ( a seed type). He had surgery in February 2009 but the cancer returned within a month & has increased in size. He has difficulty urinating but other than that he still chases squirrels & enjoys his daily runs, meals & visits from people. He takes 2MG/ML meloxicam 2 thyro tabs for his thyroid, 2 trilostane
    for cushings disease. I have recently introduced 1000 IU vitamin D in a 50 ML dropper which I am giving once daily.
    Would that be dangerous to a dog with cushings disease?

    • Dr. Dressler

      Good question!
      I will address vitamin D at this weeks webinar:
      Thank you
      Dr D

      • Dr. Dressler

        FYI the webinar is recorded so you can listen later,

  • Victoria Cobb

    Dear Dr. Dressler, I have been told my 13 year old dog has stomach cancer. I would appreciate any advice! Thank you, Victoria Cobb

  • L. Sledge

    see above

  • http://www.solaractiveintl.com jennifer skyler

    Sun protection is important, especially when you have fair skin like i do. I found this color changing bracelet by SolarActive that changes color in the sun when the UV rays hit it. This is one of the ways i stay sun aware and sun safe. The bracelet seems to change colors faster or slower depending on how much UV the sun is emitting that day. You could probably even rig up your dog with one of these! lol
    They have color change tshirts and color changing beads as well. I got it at the SolarActive website here: http://www.solaractiveintl.com I always recommend my friends to get products like these since they really help to be sun aware. Thanks for the blog and keep up the good work I love reading! :)

  • Anon

    Cats and dogs cannot synthesize Vit D from sunlight – do some basic research from multiple sources.. check Wikipedia, ask a vet that sounds like they have a clue..

    • Dr. Demian Dressler

      Dear Anon, one of the problems with the internet is that it may not always yield the best information. Most mammals are able to synthesize (active) vit d3 from 7-dehydrocholesterol in the presence of ultraviolet B light (such as that emitted by the sun), including dogs and cats. This occurs in the skin. Perhaps a veterinary clinical nutrition text would be a source you might want to reference.

  • Jen

    Dogs and cats dont make vitamin D in their skin. That is why its an essential nutrient in the diet. We have known this for YEARS.

    Dietary vitamin D dependence of cat and dog due to inadequate cutaneous synthesis of vitamin D. How KL, Hazewinkel HA, Mol JA. Gen Comp Endocrinol. 1994 Oct;96(1):12-8.

  • Mariel

    If they don’t make it in their skin, the oil in their fur could form the pre-D, and they could ingest it by licking.

  • http://www.plentyofpuppies.com/DogVitamins/ Dog Vitamins

    Hey great article. I have a page about dog vitamins and have been looking for some good information and doing a lot of research. This is the first place where I have solid information from an actual doctor! Thanks a lot.

  • http://www.petstreetmall.com/Pet-Carriers/1651.html Hannah

    Very very helpful and knowledgeable article indeed. A friend had to deal with her dog’s Melanoma cancer and they are in the snowy weather now. Mariel does that method is effective to consume Vitamin D for dogs?

  • http://www.dogcancerblog.com Ruth J

    What about hemangiosarcoma of the spleen (vs. skin)- do you recommend sun exposure with that? And could you comment regarding Vit D synthesis in dogs due to sun exposure in response to the earlier readers? Thank you

  • Ken

    If people DO NOT understand that some areas of the country DO NOT get hardly any sunshine in the Winter (thus no Vitamin D), then how can one expect these idiots to give any type of accurate answer? Truly amazing. I live in Upper Michigan where it is 10-15 degrees outside each day with NO SUNLIGHT during the winter. Yet some idiots tell me to give my dog sunlight? I tell them to get a brain.

  • Peter

    In the article it is stated that “Sunlight has a dramatic effect on active vitamin D levels in the blood”. It is my understanding that this is untrue therefore I would be pleased to be supplied with a reference that I am wrong. The following from http://www.sciencedirect.com/science/article/pii/S0016648084711543 : “…the dog and the cat are…not able to synthesize vitamin D3 adequately in the skin and are mainly dependent on its dietary intake…. Thank you.

  • marco

    sun is useless on sick and obese, i have hbv infection (same is reported on hcv, hiv and cancer) and the tropical sun is useless to make any vitamin d in these cases.

    in our hbv community we found that only 10.000iu d3 daily can rise vit d on sick people (maybe healthy ones can get it from sun) and we also observed that high calcium baseline even decreased on 100ng/ml (highend of normal vit d).simply by checking vit d and calcium monthly we found how untrue is the effect on calcium within normal vit d ranges

    i guess dogs is about the same

  • L. Sledge

    My pal is Charley. He is a mix of 80% Rottie, 12% German Shepard and 5% Chow—black spotted tongue, and 3% who knows. He is 65 pounds and 13 years old. One month ago, he had a tumor removed from his tongue the size of a golf ball. We didn’t get to clean margin. So far, it hasn’t returned. Full body Xrays at the time showed nothing in the lungs or elsewhere. He sleeps more than usual but shows the “puppy” hops every now and then. No accidents in the house yet. We have opted for the holistic approach. Still very interested in diet and vitamin D plus any noninvasive approaches. Charley is my best friend and I need to help him. Please help me. Thank you, Larry Sledge