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.