Does Grain Free Dog Food Cause Heart Disease?
Many pet parents choose to go grain free in an effort to find the healthiest possible food for their pets, so naturally when the FDA announced in July 2018 that they were investigating a potential link between grain free dog food and heart disease, it's no wonder many were left wondering whether they had made the right choice.
The FDA released an update regarding their investigation into this issue on 27th June 2019 and while some common dietary factors between many of the cases have been identified, particularly the feeding of grain free diets and diets containing peas and/or lentils, the root cause is still yet to be determined. At this stage there is still no definitive evidence to link the cases to diet altogether, although identifing a specific dietary link between cases remains the primary focus of the investigation.
What do we know?
In the last few years, veterinary cardiologists in the United States have reported seeing increased rates of a deadly heart condition, dilated cardiomyopathy (DCM), in Golden Retrievers and breeds which are not typically predisposed to DCM in general. Frequently these dogs were noted as being fed what veterinary nutritionist and professor at Cummings School of Veterinary Medicine at Tufts University, Dr Lisa Freeman, terms: 'botique, exotic or grain free' diets, or BEG diets for short. BEG diets tend to be manufactured by smaller, boutique companies and typically contain exotic protein sources such as kangaroo, bison, venison as well as grain free carbohydrate sources including chickpeas, lentils and tapioca.
What is Dilated Cardiomyopathy?
Dilated cardiomyopathy (DCM), is a condition affecting the heart muscle in dogs, causing it to become enlarged and less effective at pumping blood. Eventually, as the heart becomes overloaded and is unable to keep up with the needs of the body, congestive heart failure develops. Dogs affected by DCM may show no signs in the early stages, with dogs in later stages of the disease displaying symptoms such as lethargy, reduced appetite, increased breathing rate, shortness of breath, cough, abdominal distension or collapse.
How is taurine involved?
Some dogs who developed DCM while being fed a BEG diet turned out to have low taurine levels, and their condition improved with taurine supplementation and diet change, which lead cardiologists to suspect that taurine deficiency might have been playing a role. Interestingly some dogs without reduced taurine levels still improved with supplementation and diet change, so while it appears that taurine could be involved there may be other cases where separate and unknown dietary factors are also playing a part.
A Brief History of Taurine in Pet Food
Up until the late 1980s, DCM was a much more common condition in pet cats than it is these days. In 1987 a groundbreaking study by Pion et al demonstrated that taurine deficiency and DCM in cats was linked, leading to an increase in the minimum required taurine content of cat foods, which was followed by a decrease in the number of cats developing DCM.
Since then, veterinary cardiologists have postulated that a predispisition to taurine deficiency in some dog breeds could increase their risk of developing DCM. There is still uncertainty as to which ingredients or diet properties may be involved, and it is also clear that for dogs there are other genetic and breed factors involved with the risk of developing DCM.
Not all dogs who developed DCM were fed a grain free diet
Importantly, it's worth noting that of all the dogs thought to have diet related DCM, not all were fed grain free and some were fed homemade diets instead of comercially prepared products. From the most recent update regarding the FDA's investigation into this issue, 91% were found to be fed a grain free diet. Interestingly 93% were fed a diet containing peas and/or lentils, however it is worth noting that many grain free diets contain legumes such as peas or lentils as an alternative carbohydrate. The significance of peas and/or lentils as an ingredient in the diets of affected dogs is as yet undetermined.
At this stage research is still ongoing and it is unclear as to the underlying cause or causes of the reported cases of diet related DCM. Indeed it is still unproven whether there is a definitive link to diet at all. Some possible theories for a cause of DCM related to BEG diets include nutritional imbalances in the foods themselves, unknown effects of certain exotic ingredients such as legumes, fruits, flaxseeds etc or even potentially an unknown toxin.
But if a food meets the AAFCO requirements for maintenence, how can there be a nutritional imbalance?
While there are minimum specified nutrient requirements for essential nutrients in dog and cat foods, this does not take into account the bioavailability of said nutrients. Bioavailability essentially refers to the body's ability to actually utilise a nutrient within a food and can vary from one source to another. Bioavailability can also be affected by the amount and type of fibre in a diet. Essentially this means while the nutrient is there in sufficient amounts, it may not be usable by the body. There is less data available regarding the nutrient profiles and nutrient bioavailability from exotic ingredients and protein sources such as kangaroo or bison than traditional ingredients such as chicken or beef. Pair this with the fact that smaller 'boutique' pet food brands may not have the means to conduct a detailed analysis on these exotic ingredients, and the case for nutritional imbalance or deficiency as a cause becomes a potentially plausible, if unproven one.
Is grain free food safe for my dog?
For the moment the possible link between DCM and grain free or BEG foods in general is still unclear, the FDA in the United States is currently conducting an investigation into the issue. As yet there are no recommendations from the FDA to discontinue feeding grain free foods, although for dogs who have been diagnosed with DCM or are known to be at higher risk, we recommend discussing the best choice of diet with their treating veterinarian.
At this stage there is no conclusive evidence to suggest feeding your dog a complete and balanced, commercially prepared grain free diet puts them at a higher risk of developing DCM. Many pet parents report seeing an improvement in their dog's health and wellbeing following a switch to a boutique, exotic or grain free food and they can offer benefits such as increased levels of beneficial nutrients, such as omega fatty acids, probiotics and antioxidants, as well as being suitable in some cases of dietary sensitivity.
Rotational feeding may help protect against nutritional deficiencies
For pet parents concerned about nutritional deficiencies, feeding a rotational diet offers a great way to provide your dog with some variety while also reducing the risk of a deficiency in particular nutrients developing from feeding a particular diet over an extended period of time. Rotational feeding involves offering your dog a combination of high quality diets, ideally varying protein sources and formats (eg. dry, freeze dried, wet). In the beginning, you would change food less regularly and provide transition meals to allow the gut to adjust, however with time you could feed your dog a different food every day or every few days - whatever works for you!
US Food & Drug Administration. (2019, June 27).FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy. Retrieved from https://www.fda.gov/animal-veterinary/news-events/fda-investigation-potential-link-between-certain-diets-and-canine-dilated-cardiomyopathy
Freeman, L.M, Stern, J.A., Fries, R., Adin, D.B. & Rush, J.E. (2018) Diet-associated dilated cardiomyopathy in dogs: what do we know? Journal of the American Veterinary Association, 253 (11), 1390-1394. doi:10.2460/javma.253.11.1390
Kaplan, J.L., Stern, J.A., Fascetti, A.J., Larsen, J.A., Skolnik, H., Peddle, G.D., ... Ontiveros, E. (2018) Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. PLoS ONE 13(12), doi:10.1371/journal.pone.0209112
Freeman, L.M. (2018, November 29). It's Not Just Grain-Free: An Update on Diet-Associated Dilated Cardiomyopathy. Retrieved from http://vetnutrition.tufts.edu/2018/11/dcm-update/.
Freeman, L.M. (2018, June 4). A broken heart: Risk of heart disease in boutique or grain-free diets and exotic ingredients. Retrieved from http://vetnutrition.tufts.edu/2018/06/a-broken-heart-risk-of-heart-disease-in-boutique-or-grain-free-diets-and-exotic-ingredients.