Grain-free Diets and Heart Disease in Dogs

For some years now, grains such as wheat and corn in dog and cat foods have been demonized by many in the alternative medicine world. There has never been any real scientific evidence to support all the hysterical claims about grains as a risk factor for disease, and there is no reason to believe so-called “grain-free” diets have any health benefits at all. Sadly, many pet food companies have chosen to play into this fad by offering such diets and marketing them in ways that suggest they are better for our pets than diets which contain such ingredients. This has led to an increase in potato and taro root and other alternative carbohydrate sources in dog and coat food with no evidence that these are in any way safer or healthier than the much-despised wheat and corn.

I’ve been fairly neutral towards this diet fad. While I have always maintained that the claims about grains are implausible and unsubstantiated, I assumed that as long as the alternative diets met the established nutritional standards for pet foods generally, they were probably no worse than existing diets even if there was no reason to think they were better. I have a natural dislike for pseudoscientific fads, but I still believe in judging claims on the evidence, and without any evidence I refrained from any judgement against such diets.

Earlier this year, however, I saw a couple of golden retrievers with an unusual heart condition, known as Dilated Cardiomyopathy (DCM). This can be caused by a variety of genetic and environmental factors, but these cases were a bit atypical, and after some testing we discovered that these dogs had a deficiency in an amino acid called taurine, which has been associated with DCM. This deficiency is unusual in dogs fed balanced and complete commercial diets, and these dogs were on commercial grain-free diets that supposedly included all necessary nutrients.

Further investigation turned up low taurine levels in some additional dogs of the same breed and on similar diets. Since then, the cardiology and nutrition services at the UC Davis School of Veterinary Medicine have begun investigating the potential link between grain-free diets and DCM in golden retrievers, and potential other breeds. The Food and Drug Administration (FDA) has issued a notice warning pet owners about the potential that diet, including grain-free diets and those with unusual primary protein sources or other uncommon ingredients, may be a risk factor for this disease, and the national media has begun to raise alarms about this issue.

Dr. Jennifer Larsen, a nutritionist at UC Davis, has written an excellent summary of the nuances of this issue, and she has agreed to let me share some of it here:

Taurine is not required to be present in dog foods. Taurine is an amino acid that is not nutritionally essential for dogs; however, there are dietary factors (such as protein source, fiber type and concentration, and cooking or processing methods) and individual dog characteristics (such as breed and calorie needs) that impact how efficiently taurine may be made and used by the body. The sulfur amino acid content and bioavailability in food is important though. The problem with dietary deficiency-related cardiac disease is multifactorial and is not just seen in goldens.

1- in many grain free diets, legumes are used to provide the carb (starch) but also protein and fiber – you cannot tell which ingredients are providing various proportions of nutrients from an ingredient list

2- legume protein is low in sulfur amino acids (methionine and cystine- the precursors for taurine synthesis)

3- some fiber types/concentrations increase fecal taurine content and promotes bacterial degradation of taurine (dogs and cats must use taurine to conjugate bile acids) so taurine recycling is not as efficient and more is lost

4- dogs need an adequate supply of precursors and to be able to make taurine fast enough to replace obligatory as well as excessive losses. When Newfoundlands and beagles were compared (during the Investigation into the lamb and rice issue with DCM in the 90s), it was found that Newfoundlands made taurine more slowly, so there are differences among breeds and probably individuals

5- dogs with lower than predicted calorie needs (“easy keepers”) also might not eat enough food and therefore enough protein to supply adequate precursors

6- some grain free diets (and other types of diets), are not high in protein (and therefore sulfur amino acids) since they use more expensive exotic or uncommon sources.

Any of these or a combination may impact taurine status in the dog.

There have been recent cases seen in our hospital and elsewhere of dilated cardiomyopathy secondary to taurine deficiency in dogs that have been associated with commercial diets containing certain ingredients (such as legumes – beans, lentils, and peas – and root vegetables – white and sweet potatoes). Data collection and interpretation is ongoing for these recent cases.

In the past we have also seen cases of dilated cardiomyopathy and taurine deficiency in dogs eating home-prepared diets (with either cooked and raw ingredients and those with and without meat), and other commercial diets with various ingredients and nutritional profiles. Some of those cases and investigations have been published (others can be found on PubMed):

Backus RC, Cohen G, Pion PD, Good KL, Rogers QR, Fascetti AJ. Taurine deficiency in Newfoundlands fed commercially available complete and balanced diets. J Am Vet Med Assoc. 2003 Oct 15;223(8):1130-6.

Fascetti AJ, Reed JR, Rogers QR, Backus RC. Taurine deficiency in dogs with dilated cardiomyopathy: 12 cases (1997-2001). J Am Vet Med Assoc. 2003 Oct 15;223(8):1137-41.

Tôrres CL, Backus RC, Fascetti AJ, Rogers QR. Taurine status in normal dogs fed a commercial diet associated with taurine deficiency and dilated cardiomyopathy. J Anim Physiol Anim Nutr (Berl). 2003 Oct;87(9-10):359-72.

Bélanger MC, Ouellet M, Queney G, Moreau M. Taurine-deficient dilated cardiomyopathy in a family of golden retrievers. J Am Anim Hosp Assoc. 2005 Sep-Oct;41(5):284-91.

Freeman LM, Michel KE, Brown DJ, Kaplan PM, Stamoulis ME, Rosenthal SL, Keene BW, Rush JE. Idiopathic dilated cardiomyopathy in Dalmatians: nine cases (1990-1995). J Am Vet Med Assoc. 1996 Nov 1;209(9):1592-6.

Due to the variable and sometimes incomplete reported diet history information for recently affected dogs, the inability to predict diet performance in any individual from nutritional profile/ingredient information, and lack of proof of causation, it is not possible to identify specific dietary characteristics nor specific products that are or are not recommended at this point.

If you have concerns specific to your own pet, we encourage you to reach out to your primary care veterinarian for guidance, possible testing (which may include a physical exam, blood tests, radiographs and/or an echocardiogram), and dietary recommendations. Taurine status can be assessed by measuring it in blood. Ideally two blood samples are assessed at the same time, and collected *prior to changing the diet or adding supplements*: 1) heparinized whole blood and 2) plasma that has been centrifuged and separated from blood cells immediately after collection.

Bottom Line
Nutrition and metabolism are complicated, and the exact relationship between dietary composition, breed genetics, and other factors leading to DCM is not yet clear. It is too early to say with certainty whether the diets are the primary cause of DCM in these dogs or whether other breeds may also be at risk. However, it is clear that the idea behind the health claims for grain-free diets is speculative at best and very likely untrue. Extreme diet fads hardly ever turn out to be a good idea in people, and the same is probably true for pets.

If you are feeding a grain-free diet, there is no need to panic. If you own a golden retriever or other breed that has been shown to be develop DCM in the past, it makes sense to talk to your vet and potentially have taurine levels tested or other diagnostics done depending on the circumstances. The diet you are feeding may be perfectly fine, but it is also probable not any better than any other diet with more conventional ingredients, and there is now some small indication that it may place some dogs at greater risk for this preventable disease.

The links above to the FDA and UC Davis Vet School will provide more information.

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74 Responses to Grain-free Diets and Heart Disease in Dogs

  1. Lynne says:

    Hi Louis,
    there’s a big difference between healthy leafy green veggies & starchy legumes, a big different.. Maybe Skeptvet can explain further..

  2. skeptvet says:

    The original study was pretty weak (based on owner recollections of what they fed), and there is no controlled evidence that leafy green vegetables reduce disease risk in dogs. That said, there is no plausible reason to think they will do any harm for most dogs either. The issue with DCM is a very limited one that hasn’t been thoroughly worked out, so I don’t yet think it’s a reason to avoid any particular food except in very limited circumstances (e.g. I probably wouldn’t feed a Golden retriever a grain-free diet).

  3. louis says:

    Ok, thank you! Will give it a try, then and anyway.

  4. Doug says:


    I have an 11 year old mixed breed weighing 75lbs whose been fed grain-free for years, mainly because I’ve noted that a lot of other products with grains contain a lower crude protein content.

    I assume that the grains contribute a meaningful amount of protein to the total the food contains. The issue I have is whether it’s poor practice to feed a senior dog less protein (24% vs 32%).

    I’m concerned about the dog loosing muscle mass as well as having good energy levels.

    I was prescribed a Veterinary Diet that has chicken by products as the only animal protein source, the first ingredient being brewer’s rice. My dog was on that for about a month and seemed to me to be more lethargic than usual.

    I went back to a grain/meat version of the brand he was eating that contained 24% crude protein, which seemed to leave him unsatisfied and still hungry. The big-bag store employees told me that high protein diets are bad for older dogs and can make them fat.

    Would you please provide with your take on the high vs low protein, as the grain-free foods contains the most protein, as well as what you believe to be a healthy amount of protein for an older dog.

  5. skeptvet says:

    There is not much evidence that the protein requirments of senior dogs are that different from those of younger dogs, and in fact lower protein levels can contribute to age-related muscle loss. Here is an article from the Tufts Univ. nutrition specialists, as well as a research paper looking at this topic:

    “Although it is a common belief, reduced dietary protein is not beneficial for the healthy older dog or cat. In fact, lower protein diets for older dogs and cats may have negative effects by contributing to muscle loss. Therefore, dogs and cats should not be fed a reduced protein diet just because they are aging. The “optimal” protein level for older dogs and cats, however, is still controversial. Some companies make senior diets with lower protein while others actually make their senior diets with increased protein. Just like there’s no evidence for benefits of a low protein diet, it also is not clear that high protein diets are beneficial or even optimal for seniors.”

    Cornell Vet. 1985 Apr;75(2):324-47.
    Nutrition and metabolism of the geriatric dog.
    Sheffy BE, Williams AJ, Zimmer JF, Ryan GD.
    Sixteen 10-12-year-old and eight 1-year-old dogs were studied over a two year period to determine comparative differences in physiological response to 4 diets varying in protein content and percentages of energy contributed by protein. The ability of old dogs to utilize nutrients as supplied by these foods was not significantly different from that of young adult dogs. Except for indices of mitogenic stimulation and serum urea nitrogen (SUN) other physiological parameters studied were not affected by the diet fed. Regardless of diet, old dogs had significantly higher serum levels of cholesterol, phosphorus and alkaline phosphatase and had lower indices of mitogenic stimulation than did young dogs.

  6. Lynne says:

    Hi Doug,
    I feed my 10yr old a high protein -35%, low/med fat -13% – Wellness Core Large breed dry grain free kibble…

    This Wellness Core Adult Large Breed formula has made a big difference, my dog acts like a young pup again, feels good & he keeps up with me on our daily walks..
    Make sure there’s at least 3 meat proteins as 1st, 2nd & 3rd ingredients then a carb.
    Also Look at “Canidae Pure Meadow Senior” formula & “Wellness Core” has a Senior formula but the Large Breed adult dry formula has more meat protein & the Core Large breed formula’s is high in Glucosamine & Chondroitin helped with my dog Arthritis in lower back & hip..

  7. L says:

    This is not DFA. Keep your sock puppets over there. Seriously.

    The best thing anyone can do for a pet is to find a veterinarian that you trust, bring your dog in for annual checkups/routine care and listen to their advice If you still have doubts, seek another opinion (veterinarian). Not the internet.
    My 2 cents.

  8. skeptvet says:

    Yes, that’s a weird study. The assumption behind the paper is that raw diets should be better even though there is no scientific evidence and only anecdote to support such a belief. They put “natural” and “unnatural” in quotes, appearing to recognize these are pretty meaningless terms as far as predicting health effetcs, but then they still seem to buy the idea that public belief and anecdote about such differences is a reasonable basis for hypothesizing health benefits to “natural” diets. Even after the serious (in one case fatal) negative outcome from the raw diet, the authors still seem to believe this (e.g. “The results of this study have shed further light on the creation of an optimal
    natural diet for maintaining feline intestinal health. This represents a step towards the creation of a “gold standard” diet that may be of benefit for the management of IBD in
    the cat.”). They are willing to admit that the results illustrate the potential risks of raw diets (because how could they not when all the cats developed a potentially fatal disease?), but they still seem sympathetic to the underlying idea that “natural” is a meaningful term and might

    Also, all of the animals had known, untreated intestinal parasites and potentially pathogenic bacteria, which doesn’t really represent a normal, healthy pet cat population. Why wouldn’t you treat these to see what the effect of the diet might be on normal, healthy cats?

    This is certainly an excellent illustration of why the reasoning behind “natural” nutrition and medicine doesn’t make sense and doesn’t work, but it seems like the authors themselves don’t entirely get the lesson.

  9. Michael Kalish says:

    It appears to me that the problem is taurine deficiency. My “research” suggests that there are many sources of taurine, including chicken and other meats, so I’m not sure why this is a “grain” issue. There are also taurine supplements available if an animal isn’t getting enough and can’t synthesize, but a good quality diet will offer taurine, with or without grains…or so my sources indicate.

  10. skeptvet says:

    Unfortunately, it isn’t that simply. As I discuss in the article, dogs and cats do not normally require taurine in the diet at all; they make it from other amino acids. These diets are not deficient in taurine because there is not required level of taurine in the diet. And, in fact, nearly half of the DCM cases were not taurine deficient, so there is more going on here. However, the ability to produce and retain taurine is affected by both genetic and dietary factors. The suspicion is that for individual dogs with marginal ability to make taurine or an increased tendency to excrete taurine (which are genetic characteristics) diets which have normal levels of the precursor amino acids may not be sufficient, and diets which have legumes and other ingredients which may increase taurine loss may lead to problems. Of course, one can always supplement, but one shouldn’t have to, and there is clearly something about these diets that is contributing to the problem.

  11. Deb M says:

    I have been feeding my dog a grain free sweet potato based dog food from Costco on the advice of my veterinarian because of allergies. He’s a 10 year old Rhodesian Ridgeback what is the right thing to do? I don’t want him miserable from his ears and skin being inflamed but I don’t want him dead from a taurine deficiency! I need to change food in any case because he has diabetes I just don’t know which one is best any advice, kind of doubting his vet now!

  12. skeptvet says:

    Again, there is no evidence that grains are a problem for most dogs, and even those with food allergies are much more likely to be allergic to other ingredients. In the absence of enough information for every possible breed to know what the risks are, your best option is to talk with a veterinary dermatology or nutrition specialist about your options.

  13. Lee L. says:

    Hi Skeptvet!

    I’ve been reading your blog for some time, and haven’t ever really chimed in. I do enjoy your commentary on these subjects. Also, I agree with your “science first” approach to, not only nutrition, but the general health and well being of our pets.

    I purchased a French bulldog puppy in December, and from the beginning, she’s had nothing but GI problems. I’ve spent a massive amount of money (over $13,000) on veterinary care, as well as foods. In short, she has had soft stools, diarrhea, blood in stool, giardia, etc. A few weeks ago, she had and upper endoscopy and colonoscopy, with biopsies sent to Texas A&M for pathology. Results came back, and IBD was the diagnosis, with several sub-issues. These issues are apparently not uncommon for the breed.

    With that, she’s been on hydrolyzed protein diets, limited ingredient diets, standard fare diets, all with no change in bowel habits/symptoms. We’ve added psyllium husk fiber to her food just to maintain some form for her stools. This helps, but basically makes her stools a soft jello.

    I’m being told by many in the French bulldog community that grain-free/raw diets are indeed the best diets for Frenchies. Even breeders say that grain-free, minimally is the way to go. My vets both disagree with that evaluation. They insist, as do you, that current mainstream dog foods, containing grains, are the safest, most balanced, even though they aren’t perfect.

    My question is, considering what this pup has endured, if it’s your dog, do you accept the risk of the possibility of a potential problem with feeding grain-free/raw diets, or do you accept the risks/long term side effects involved with lifelong steroid/medicated treatments? I fully understand that if I were to try one of these diets, she may not respond positively to it, but I guess I’m asking, would you consider it worth a try?


  14. skeptvet says:

    I suspect the risks of a grain-free diet are very low, so that is less the problem than the fact that there is absolutely no reason to believe it should or will work. The hydrolyzed protein diet is a grain-free diet, as are many of the limited ingredient diets, so if you have used those, you have already done a grain-free diet without success.

    As for raw, again there is absolutely no plausible reason why it should help and no evidence that it does. Unlike grain-free, however, it certainly does have risks, so as frustrating as your situation is, I can’t agree that it is “worth a try.” I certainly understand why you feel that way, and I wouldn’t blame you for grasping at this or other straws, but the opposition you are seeing to the idea is because it is risky and frankly makes no sense. If someone tells you that Lourdes water or Reiki or any other magical method are “worth a try,” this advice would not be any less plausible than a recommendation for raw diets.

    Good luck!

  15. Lee L. says:

    Re: “the hydrolyzed protein diet is a grain-free diet”… Brewers rice is the number one ingredient. Is that not considered a grain??

    Thanks for the advice! I’ll need some of that good luck for sure!

  16. Lee L. says:

    Also, all of the “limited ingredient” products I’ve fed have included:

    Ground Rice
    Canola Meal
    Oat Meal

    I don’t think I’ve given anything that’s grain-free yet.

    Thanks again, and sorry to use up the comments! I’m done, I think!

  17. skeptvet says:

    It depends on which hydrolyzed protein diet you get. Several are grain-free, but some do have corn or rice in them. Again, the hydrolysis breaks down the proteins in a way that should prevent any adverse reaction, so the specific ingredients don’t actually matter in terms of true food allergies, but it is possible to use a grain-free hydrolyzed protein diet if you want to.

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  19. Gwen says:

    So which dog food is the best?

  20. skeptvet says:

    No such thing. Life is far too complicated for there to be a single “best” food for every, or even any dog. Most dogs will thrive on many different commercial diets, and there is always some trial and error involved in finding one that works for each individual dog.

    You might be interested in the book Dog Food Logic, which discusses the decision-making process around dog food in depth.

  21. Jon says:

    Lol. The ole ‘I don’t know so I’ll just make an ignorant blanket statement’. There are plenty should you put fourth just the smallest amount of effort into typing into a Google search box.

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