Dilated cardiomyopathy in dogs: Is diet a cause?

5 years ago, the US Food and Drug Administration (FDA) launched an investigation into a spike in cases of canine heart disease thought to be related to diet. But are we any clearer about this strange disease?

DCM: the basics

Dilated cardiomyopathy (DCM) is a type of heart disease where the heart becomes enlarged and stops pumping effectively. Symptoms include coughing, inability to exercise, or fainting episodes, and can include sudden death.

Some dog breeds (mostly large and giant ones) are more prone to DCM. There is a strong genetic link, with predisposed breeds including Doberman Pinschers, Irish Wolfhounds, Great Danes, Boxers and Saint Bernards.

However, genetics isn’t the only cause of this complex disease. Diets low in taurine can cause DCM, and it was previously thought that hypothyroidism was a cause.

So, what’s changed?

In 2018, the FDA released a statement alerting pet owners and vets to a recent rise in DCM cases in non-predisposed breeds. They started an investigation into the dogs’ diets as a possible cause.

Following this announcement, over 400 further cases of DCM were reported to the FDA. However, despite over 1,000 cases being reported, this is still a very small proportion of dogs in the US. Other countries did not report a large number of additional cases, and the numbers reported to the FDA reduced again by 2021.

It is possible that this ‘spike’ in cases was more related to increased awareness than to an actual problem. This is supported by research from the University of Missouri showing no significant increase in DCM cases in the US from 2000-2019, despite a huge rise in grain-free feeding. It’s worth noting that this study was on a national scale – a complex cause including geographic factors may have impacted the increase in cases the FDA spotted, which would not have shown in the research.

There is more evidence that these cases were above the usual DCM reports. For one, the cases reported to the FDA did appear to be different from ‘normal’ DCM. They were reported in non-standard breeds and – unlike normal DCM, which is considered irreversible – some of these dogs improved once their diet was switched, as reported in the Journal of Veterinary Cardiology. So, it’s likely that this was an ‘outbreak’ of a different form of DCM.

Is diet to blame?

There has been a huge amount of research done on the link between diet and DCM, with no definitive answer.

A very recent study from researchers at the University of Illinois found measurable changes in dogs’ heart function after just 28 days on a diet formulated with pea flour, but not when they were fed diets formulated with lentil flour, rice flour, or a generic commercial food. It was a very small study, with just 8 dogs, but does add weight to the link between diet and non-hereditary DCM.

Research published in Nature looked at the molecules present in variable amounts in diets associated with DCM versus those that weren’t. They spotted 111 statistically significant differences and found that most of these were attributed to 4 ingredients – the presence of peas and lentils, or the absence of chicken/turkey and rice. It’s likely that it’s a complex combination of dietary molecules. A further study looked at the metabolites in the blood of dogs being fed DCM- DCM-associated diets versus traditional diets, and found 17 metabolites that differed significantly.

Despite all this excellent research, no definitive cause of DCM in these dogs has been found. While it’s still thought that diet could be part of the answer, it is likely that it’s a complex interplay of genetics, diet, and other diseases. Cases seem to have dropped again, causing the FDA to stop giving routine updates on the situation.

Where do we go now?

Research into this is ongoing. The FDA is continuing to monitor the situation but doesn’t believe there’s enough evidence to make any diet recalls. Everybody who works with or lives with dogs should be mindful of the symptoms of DCM and visit a vet if they have any suspicions, as early diagnosis improves outcomes.