Doctor's Note

For more on lymphoma risk factors, check out these videos:
Food Antioxidants and Cancer
Chicken Dioxins, Viruses, or Antibiotics?
Eating Outside Our Kingdom
Raw Broccoli and Bladder Cancer Survival

And check out my other “HHH” videos (Harmful, Harmless, or Helpful?) – listed below the post.

For more context, see my associated blog post: Which Pets Improve Children’s Health?

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  • Michael Greger M.D.

    Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. And check out the other “HHH” videos (Harmful, Harmless, or Helpful?). Also, there are over a thousand subjects covered in the rest of my videos–please feel free to explore them as well!

  • amylee83

    Hi Dr. Greger!
    Is the harmfulness of contact with pigs and cows just based on handling their raw meat or on having them living around you, petting them, etc.? I am confused by why contact with cows and pigs while they are living would be harmful and contact with other pets is not, especially considering what you were saying about bovine leukemia and the existence of feline leukemia. I know that you said most herds in the US are affected by the virus. Could it be that feline leukemia is less prevalent and therefore a lower risk factor?

  • HereHere

    I second amylee83’s question. Is it contact with the live animals, or just contact with dead cows and pigs that increases risk?

    • Toxins

      Amylee83 and HereHere,
      to answer both of your questions, The study did not specifically state whether it was handling dead animals or the meat, it just said in contact and working with them, to quote the study, “Exposure to cattle for ≥5 years was associated with an increased risk of [lymphoma] as was exposure to pigs for all [lymphoma]” The study did specifically state that people who had dogs, cats or both, were at lower risk for lymphoma. “Given the evidence that animal exposure during infancy may reduce the prevalence of allergic sensitization and allergic disease later in childhood, it is possible that the association between pet ownership and [lymphoma] may be related to altered immune function and desensitization to allergens.”


    As equally lovable as cattle is to our domestic pets, unfortunately cattle is not treated as kindly! Note the deplorably unsanitary conditions they are subject to! These poor sentient creatures do become distressed, stressed and sick from their chronic environmental conditions. At our Dermatology clinic we have treated patients with strange virus in their nostrils and other orifices. They raised their own chickens and pigs.
    See in-food/ ! You may also be interested to read Dr. Greger’s “Bird Flu: A Virus of Our Own Hatching” available on Amazon. The animals that people eat are coming back with a vengeance to teach us a painful lesson!

  • ellenkao

    Dr. Greger,

    We are in the process of adopting a dog. Do you know of any scientific studies that support whether or not dogs would be fully nourished by a 100% vegetarian diet?

    Thank you!

    • AmandaJC


      I can tell you that dogs can absolutely thrive on a vegan diet!  I have two hardy (rescue) pit bulls that have been vegan for nearly 3 years.  They have not only maintained weight but even put a few pounds on.  Cats and dogs both belong to the Order Carnivora.  However, only a very few species are obligate carnivores, which means they MUST have meat to survive.  Felines are one of those species.  Dogs, on the other hand, are like humans and are not obligate carnivores.  This means they can achieve all their nutrient needs through plant sources.

      I feed my dogs Natural Balance Vegetarian Formula (it is actually vegan). It contains no soy, wheat, corn, or gluten, all of which so many commercial foods are full of and are common allergens (not to mention the nasty rendered protein).  My thoughts are if meat can cause us so much damage, why would I want to feed that to my dog with different health expectations? 

    • 2 vegan dogs

      2 of my dogs are on a vegan diet, and they are doing great. They are very playful, active, full of energy. I did extensive, unbiased research on it (because putting a dog on a vegan diet does sound crazy on the surface) but we are living during times where scientists are able to mimic human organs, including human heart so compared to that, coming up with a vegan dog formula that meets all the nutrients a dog needs is pretty easy, I’d say. I personally feed my dogs “V-dog.” There is also EVOLUTION DIET; they carry vegan cat food, too.

    • sryan

      Hi Dr Greger,

      I also wondered about this because my husband and I were doing so well without animal products and our labrador retriever seemed to have so many sensitivities to foods and the environment. I fed our labrador a vegan formula dog food for more than a year. She thrived no matter what she ate. We have always given her healthy whole people food which she loves (vegies, fruit, etc). Because I couldn’t find research to support the vegan path for her I chose to give her organic meat as a supplement once a week. This seemed like a good idea particularily in line with the 5-10% which Colin Campbell suggests as a maximum. She lived to be nearly 15 years old so I think her diet agreed with her.
      Susan Ryan
      PS I always chose a higher end dog food for her with the least amount of ingredients like just venison and potato (b4 vegan food).

      • Thea

        syran: I’ve been feeding my dog a vegan kibble for almost 4 years now. (I chose the brand v-dog.) Not only has my dog’s blood work come back showing that he is in great health (for his age), the kibble also cleared up some long-time problems my dog had (like peeing blood). He is an almost 10 year old Great Dane. I’ve heard many other anecdotes of dogs on good quality (very important!!! check out this page for a free e-book on vegan dogs: vegan kibble who went on to live very long, healthy lives for their breed.

        I’m aware of a study done on working sled dog Huskies. It was a short-term, very specific study and I can’t remember the details. I also can’t find it right now. (Argh!) As memory serves, the study involved feeding the dogs either their regular diet or a vegan one. The ones fed a vegan diet had no difference in performance or blood work or whatever they were measuring.

  • HereHere

    ellenkao, I would say the most significant report on the diet of dogs and cats was done by the National Research Council of the National Academies, Committee on Nutrient Requirements of Dogs and Cats. The summary for dog owners states:
    A: Because dogs are descended from omnivores, they
    are not strict meat eaters. They are remarkably adaptable to a wide range of ingredients, texture, and form in terms of what they will eat. Though many dogs may prefer animal-based protein, they can thrive on a vegetarian diet. Regardless of whether the protein comes from plant or animal sources, normal adult dogs should get at least 10% of their total calories from protein. Older dogs appear to require somewhat more protein to maintain their protein reserves, perhaps as much as 50% more.” p.11
    It appears that many cats can do well on a supplemented vegan diet (arachidonic acid and taurine), especially if low in magnesium and a urinary pH between 6.1 and 6.6, but the veterinary community is reluctant to endorse this because cats are physiologically carnivores, whereas dogs are physiologically omnivores. You will find some great brands of dog food available by mail, including Ami, VegePet, and in pet stores, eg. Natural Balance.

    • Cats are “Obligate Carnivores”. Why do people think that just because THEY are vegan, their PETS need to be vegan too?

    • NatureLover

      Check out Ami, Evolution, Wysong cat food, some are vegan, and have info about nutritional needs on their websites. Sounds like female cats can be vegan with care, and some male cats can be as long as you watch their bloodwork.

  • Thatsleepguy

    Geez I grew up on a hog production farm. Karma. When it was time for me to take over.. well I closed it. No more pigs will die on that land.

  • ellenkao

    HereHere, thank you for the response. We found a local store that was able to order the vegan dog food for us. I will look for the study you referenced. Thank you again. :-)

  • I don’t understand how pets decrease the risks? Is it because they make people less stressed?

  • tavit

    ufff… I thought I gonna dump my dog to the trash :)

  • Linda K

    I have pet house chickens…cus I recue freaking everything…I wonder about them.

    • Thea

      Linda K: “pet house chickens”, I love it! Are they house trained? How many do you have??

      Just curious. I have heard that they make great pets and can be really fun.

      • Linda K

        I have 3. 2 bantams and a med. sized breed. They wear diapers! The bantams are what I would call “old people” birds, and my other is freaking hilarious.

        • Thea

          Thanks for the reply. That’s so cool.

  • VegEater

    I’d really like to feed my Golden Retrievers a vegan diet in order to avoid cancer, since the breed is prone to get cancer, and I already know that they love peas and beans and veggies, but I’m concerned about feeding them brown rice every day because of the arsenic that’s found in brown rice. We don’t know where this brown rice is grown in the US. Brown rice grown in certain areas of the US, generally where cotton was once grown, is known to have high levels of arsenic.

  • Nate

    As someone who is 10 months into chemotherapy for non hodgkins lymphoma/leukemia i was a bit startled at the 1-3 people die from this disease statistic. Yet it is corroborated by the National Cancer Institue on their site However around 90% of those that do are 55 years+.

    • Thea

      Nate: I’m rooting for you. Good luck.