For a period of time, pet parents opted away from grain-based pet diets due to concerns with allergens or toxins. Traditional diet composition for pets relied on corn, wheat and soybeans as sources of energy and protein, whereas grain-free diets opted instead for alternatives, such as sweet potatoes, lentils and legumes. However, the increased incidence of dilated cardiomyopathy (DCM) in canines was then correlated to the growth of these grain-free diets. These occurrences led veterinarians, nutritionists and consumers alike to question the true health benefits of grain-free diets.
Taurine, DCM and their relationship in pet food nutrition
Dilated cardiomyopathy is not a new phenomenon in the pet food industry. Felines in the 1980s were found unable to produce sufficient quantities of taurine from its precursors, cysteine and methionine, to meet their needs for bile secretion and heart health. The reduction in taurine production led to an enlarged left ventricle brought on by a weakening myocardium. Without treatment, this diagnosis was often fatal, but dietary supplementation of additional taurine or other sulfur-containing amino acids was demonstrated to alleviate the causative symptoms.
Today, supplemental taurine or a minimum S-amino acids level is standard in feline diets, which has reduced feline cases of diet-related DCM. On the canine side, DCM has been prevalent in mostly larger breeds, such as Great Danes and Newfoundlands, which were thought to be genetically predisposed to the disease. However, in 2018, the U.S. Food and Drug Administration (FDA) released a statement which correlated an increase in DCM cases with grain-free diets.
There is sufficient data available to draw a corollary between DCM and amino acid imbalances in dogs, which may be associated with grain-free diets. This is potentially due to the substitution of ingredients like potatoes or peas (0.04% and 0.03% taurine) in place of more conventional grains, such as corn or wheat (0.07% and 0.21% taurine). The substitution is perhaps not as much of an issue if dogs have the capacity to convert other S-containing amino acids to taurine, but the same issues persist across this amino acid category.
For example, potatoes and peas have a combined methionine + cysteine level of 0.06% and 0.11%, respectively; while corn and wheat have 0.46% and 0.59%, respectively. Therefore, it is pertinent to identify amino acid imbalances as a known or reasonably foreseeable hazard in food safety plans for canine diets, especially those diets with relatively low inclusions of traditional grains.
Hazard analysis: Low severity, low probability
While the effects of DCM in dogs can be devastating, I still consider it to be a relatively low severity hazard. There is no direct or indirect impact on human health or wellness, so the hazard deserves to be considered lower severity than high- or moderate-severity hazards, such as Salmonella or aflatoxin, which both have a potential human health impact. However, this low severity assessment should not be confused with no severity. A deficiency in sulfur-containing amino acids has clearly been linked to DCM, and supplemental taurine has been demonstrated to help resolve this issue.
Literature is limited because most canine trials are limited by the duration of the trial and the number of dogs on each treatment. Due to this, studies evaluating the long-term effects of grain-free diets are mostly limited to retroactive epidemiological studies. While these studies have shown that extended feeding of some grain-free diets may cause taurine-deficient DCM, they do not consider co-founding factors such as exercise, supplemental food and pet treats, or lifestyle differences. The interaction of the ingredients and the availability of those nutrients to be utilized is vitally more important to canine health than the debate between grain-fed versus grain-free diet.
I typically consider the probability of S-containing amino acid imbalances in grain-free diets to be low and in grain-containing diets to be very low. In both cases, I recognized that the hazard is present and managed through proper diet formulation, which considers inclusion of all S-containing amino acids. However, I think it is important to differentiate that different energy sources may affect the quantity of taurine circulating in the canine’s body.
Grain-fed diets have energy sources with well-established nutrient profiles. Nutritionists can be relatively confident corn or wheat will release a known quantity of carbohydrates, amino acids and lipids. As novel ingredients appear on the market, extensive research must still be conducted to understand what their nutrient release values would be in each diet. The difference in my probability ranking is due to the natural lag that exists between the formulated vs. known available amino acid levels in well-established vs. novel ingredients, especially for larger breeds.
Conclusions
Dilated cardiomyopathy and taurine deficiency are sometimes used to disparage dog owners from feeding grain-free diets. However, the inclusion of novel ingredients, such as sweet potatoes and lentils, does not directly cause the heart muscle to weaken. Instead, emphasis should be placed on the availability of the nutrients themselves. Nutritionists should focus future research on the cysteine, methionine and taurine released from each ingredient, the impact processing has on the ingredient availability and, more importantly, the requirements of each of those amino acids needed at different weights and ages. A DCM diagnosis is a complex issue and cannot be boiled down to a simple grain-fed versus grain-free argument.
Briefly: Top 5 takeaways
- Dilated cardiomyopathy is not a new phenomenon in the pet food industry.
- Supplemental taurine or a minimum S-amino acids level is standard in feline diets, which has reduced feline cases of diet-related DCM.
- There is sufficient data available to draw a corollary between DCM and amino acid imbalances in dogs, which may be associated with grain-free diets.
- While studies have shown that extended feeding of some grain-free diets may cause taurine-deficient DCM, they do not consider co-founding factors such as exercise, supplemental food and pet treats, or lifestyle differences.
- A DCM diagnosis is a complex issue and cannot be boiled down to a simple grain-fed versus grain-free argument.
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