Introduction

Diet-induced dilated cardiomyopathy (DCM) is not new to veterinary medicine. The first article confirming the essentiality of taurine for cats was published in 1978¹ and the first report of taurine supplementation at correcting diet-induced DCM in a cats was published in 1987.² By the early to mid-1990s, researchers recognized that diet composition (in addition to absolute dietary taurine intake) and intestinal microflora could influence taurine status in cats.^2-4 Conversely, taurine is considered a non-essential, or dispensable, amino acid for dogs and as long as adequate levels of the sulfur amino acid precursors, methionine and cysteine, are present in the diet they are able to make adequate levels of taurine for normal heart health.⁵ Despite this, taurine-deficient DCM was seen in a number of large breed dogs in the late 1990s and early 2000s even when these animals were being fed commercial diets formulated to be complete and balanced.^6,7 It was subsequently discovered that certain breeds of dog are less efficient at converting cysteine to taurine; that diets low in total protein or that included protein sources limiting in methionine and cysteine (such as lamb, rabbit, and vegetarian or vegan diets) may increase the risk of taurine depletion; and that diets high in fiber can increase loss of taurine through feces.^8,9 Companies working with knowledgeable formulators and nutrition advisors knew about this potential problem and have adjusted their formulas and recipe accordingly for decades. That is to say that pet food companies that worked with or continue to work with veterinary nutritionists (either PhD or DACVN) and have followed their recommendations on formulation, manufacturing, and post-production testing appear less likely to be involved with the most recent DCM outbreak, whether their diet are grain-free or contain exotic ingredients, or both.

Recent Diet-Induced DCM Overview

As of November 2018, the United States Food and Drug Administration Center for Veterinary Medicine (FDA-CVM) has identified 294 cases of diet-induced DCM.¹⁰ Those that have been evaluated by the FDA-CVM appear to fall into one of three categories.

1.  Breeds that are genetically predisposed to DCM irrespective of diet, such as golden retrievers, Doberman pinschers, Newfoundland, Portuguese waterdogs, Irish wolfhounds, and cocker spaniels. These breeds have an even higher risk of DCM if fed “high risk” diets as described above.¹¹

2.  Taurine-deficient DCM in atypical breeds. A number of dog breeds that are not considered at-risk for DCM have been diagnosed with low plasma and whole blood taurine levels while eating grain free or smaller label/ boutique pet foods. It is not clear if diets that are marketed as “grain free” have other characteristics that are decreasing the bioavailability of taurine precursors; if they are changing gut bacterial populations to ones that deconjugate taurocholic acid and cause an increased loss of taurine; if there are anti-nutritive factors in the diet or individual ingredients that irreversibly binding taurine/taurocholic acid and prevent absorption/reabsorption; or these individual dogs may simply have significantly lower than “average” energy requirements and when fed at a level to prevent weight gain the animal may be under-consuming methionine and cysteine. What we have seen is that companies with high inclusions of plant-based proteins, especially protein coming from legumes such as peas, lentils, and chickpeas, appear to be more involved with this problem; of the 294 cases reported through November 2018, 191 had complete diet histories reported and 180 of those diet included peas as a primary ingredient.¹²

3.  Diet-induced DCM not associated with taurine deficiency. Most cases of diet-induced DCM fell within either expected breed predispositions or had low plasma and whole blood taurine levels, but a small percentage of cases were among dogs that did not fit breed predispositions and had normal blood work results. These dogs were eating grain free or smaller label/boutique brands, had clinical signs and echocardiographic changes consistent with DCM, and had resolution or improvement of their disease when the diet was changed. The development of diet-induced DCM in this population of dogs could be related to correcting of a relative deficiency in other sulfur amino acid metabolites (such as carnitine) with the diet change, or could indicate the presence of a cardiotoxic compound either naturally occurring in the foods or created as a secondary compound during manufacturing but it is still too early to draw conclusions.¹³

Summary

Complete and balanced commercial diets are designed to be fed as a sole source of nutrition to dogs and cats. European Pet Food Industry Federation (FEDIF) and Association of American Feed Control Officials (AAFCO) have established model guidelines for the countries and states regarding pet food labels, ingredient definitions, what can and cannot go into pet foods, and levels of specific essential nutrients required for a given life-stage.^14,15 Any pet food with an FEDIAF or AAF-CO label of adequacy must have met these guidelines, though it is up to individual manufacturers to ensure that their diets meet these requirements, and the individual nations or states to regulate and enforce these recommendations. Commercial diets labeled as having been “formulated” to meet nutritional profiles mean that the typical analysis of the diet in question meets recommended levels when compared within the formulation software, though bioavailability and digestibility can vary with ingredient quality, the specific combination of ingredients, and preparation or cooking method. Meeting nutritional levels by formulation alone does not guarantee nutritional adequacy. Pet foods labeled as having gone through “feeding trials” indicate that the diet in question has not only been formulated to meet requirements, but has also been fed to a group or groups of health dogs to demonstrated nutritional adequacy. While non-grain carbohydrates such as potatoes and legumes (especially soy and peas) have been used successfully in commercial pet foods for decades, the inclusion levels were historically much lower than what can be found in today’s grain free diets. The re-emergence of diet-induced DCM in dogs demonstrates the importance of pet food companies using knowledgeable formulators, the importance of digestibility and feeding trials especially when dramatic changes in diet formulations or ingredient ratios have been made, and the importance of not allowing food fads and marketing to supersede animal health and wellness.

References

1.  Knopf K, et al. Taurine: an essential nutrient for the cat. J Nutr. 1978 May;108(5):773–8.

2.  Pion PD, et al. Myocardial failure in cats associated with low plasma taurine: a reversible cardiomyopathy. Science. 1987;237:764–8.

3.  O›Donnell JA 3rd, et al. Effect of diet on plasma taurine in the cat. J Nutr. 1981 Jun;111(6):1111–6.

4.  Kim SW, et al. Dietary antibiotics decrease taurine loss in cats fed a canned heat-processed diet. J Nutr. 1996;126:509–15.

5.  Delaney SJ and Fascetti AJ. Basic Nutrition Overview. In: Applied Veterinary Clinical Nutrition, 1st edition, edited by Fascetti and Delaney. John Wiley & Sons, Ltd. 2012:9–22.

6.  Fascetti AJ, et al. Taurine deficiency in dogs with dilated cardiomyopathy: 12 cases (1997–2001). JAVMA. 2003 Oct 15;223(8):1137–41.

7.  Backus RC, et al. Taurine deficiency in Newfoundlands fed commercially available complete and balanced diets. JAVMA. 2003;223:1130–6.

8.  Delaney SJ, et al. Plasma and whole blood taurine in normal dogs of varying size fed commercially prepared food. JAPAN (Berl). 2003;87:236–44.

9.  Ko KS and Fascetti AJ. Dietary beet pulp decreases taurine status in dogs fed low protein diet. J Anim Sci Technol. 2016;58:29. doi: 10.1186/s40781-016-0112-6. eCollection 2016.

10.  FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy www.fda.gov/AnimalVeterinary/NewsEvents/ucm630993.htm.

11.  Kaplan JL, et al. Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. PLoS One. 2018;13:e0209112. doi: 10.1371/journal.pone.0209112. eCollection 2018.

12.  Webinar: FDA: Possible Dog Food Link to Canine Dilated Cardiomyopathy. www.petfoodindustry.com/events/612-webinar-fda-possible-dog-food-link-to-canine-dilated-cardiomyopathy.

13.  Mansilla WD, et al. Special topic: The association between pulse ingredients and canine dilated cardiomyopathy: addressing the knowledge gaps before establishing causation. J Anim Sci. 2019;97:983–997. doi: 10.1093/jas/sky488.

14.  European Pet Food Industry Federation. Nutrition Guidelines, July 2016. www.fediaf.org.

15.  Official Publication of the Association of American Feed Control Officials 2019. Oxford, IN: Association of American Feed Control Officials 2019.