Grain-free diets in dogs: a recipe for heartbreak?

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Robyn Lowehttps://www.facebook.com/veterinaryvoicesuk
Robyn Lowe FdSc, Dip AVN (Small Animal), Dip HE CVN is a small animal Registered Veterinary Nurse (RVN) who regularly writes articles for academic journals and publications for animal owners. Robyn has a passion for evidence-based medicine, volunteers for Canine Arthritis Management, runs the Veterinary Voices Public Page, and campaigns on mental health and animal welfare issues.

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One of the most common questions that veterinary professionals come across regularly in the pet food industry concerns ‘grain-free’ feeding. This diet can be chosen for a number of reasons, from people wanting to improve certain health conditions to the idea that grains in dog’s foods are poor nutritional value ‘fillers’. This actually isn’t the case, as we actually know that through domestication dogs have changed in both phenotype and genotype to their common ancestor, the grey wolf, and have the ability to digest and use grains and starch.

In the dog world there are actually only very few instances of grain ‘allergy’, one of which is epileptoid cramping syndrome, or more specifically paroxysmal dyskinesia in Border Terriers. Where a dog suffers with this disease, a gluten-free diet is genuinely warranted.

Some dogs do exceptionally well on grain-free diets, and anecdotally it appears to help with gastrointestinal issues and skin complaints – though these health benefits haven’t yet been clinically proven, and there are a few other reasons why we might see these changes on a grain free diet that is not necessarily just associated with the lack of grain.

However, there have been recent concerns over the role certain grain-free diets have been playing in cardiovascular health – particularly in relation to Dilated Cardiomyopathy (DCM), a disease of the heart that is characterised by the weakening and thinning of the myocardium or heart muscle. This causes a number of issues for dogs as the heart becomes ineffective at pumping blood – sadly including death.

Generally, risk factors for DCM are genetic, but in 2018 the US Food and Drug Administration announced that they were investigating a potential connection between diet and DCM, as atypical dogs who were not known to be genetically at risk were developing the disease.

Thankfully research in this area, despite being in its infancy, has come on in leaps and bounds. We still haven’t got the full picture, but it’s important for owners to be wary, and to remember that grains aren’t the enemy.

Picking pet food can be hard. In a 2017 assessment, some brands that claimed to be nutritionally ‘complete’ were found to be non-compliant according to European guidelines. Furthermore, home prepared diets have also been shown to expose animals to nutritional deficiencies. Therefore, feeding a good quality, complete diet is essential – one that has been formulated by a board-certified veterinary nutritionist, and has ideally undergone feeding trials too, such as from AAFCO. This could help to ensure these diets have been tested rigorously… although even then there is room for improvement.

Many companies work extremely hard to create an appropriately balanced and complete diet without having the finances to complete a feeding trial – however, while some of the grain-free diets may look good on paper, they may not translate to how our dogs actually process them, and this is where we might start seeing problems.

So, what’s been happening with grain-free diets, and why are we worried about cardiac health in dogs? Firstly, in a study using an echocardiogram to monitor and observe DCM, researchers found changes is the left ventricle size in common grain-free diets compared to grain-based diets. This suggested that those on the grain-free diets had more severe cardiac remodelling compared to the grain-based diet group.

A bowl of dry dog biscuits

In another study, dogs with DCM eating non-traditional diets experienced improvement in cardiac function after diet change –from a grain-free to a grain-inclusive diet. Survival time was significantly longer for dogs with DCM eating non-traditional diets who had their diets changed onto grain-inclusive, compared to dogs eating non-traditional diets that did not have their diets changed.

The idea that these diets can start to cause subtle issues early on is intriguing, but even more so that we also know that changing a dog onto a diet that contains grains could go some way towards improving survival time. Supporting this theory a study showed that diet change to grain-inclusive had better clinical outcomes and showed reverse ventricular remodelling. This is fairly positive news, because usually genetic DCM is not typically very responsive to treatment – the fact that diet change could improve outcome in dietary induced DCM is encouraging.

What we know, so far, is that there are some dogs of breeds not known to be genetically prone to DCM that have developed this disease, and many of these dogs have been eating diets that were grain-free, or that contain pulses and legumes such as peas, and lentils. We do not currently know the true reason for this, but it could be down to a number of factors – such as anti-nutrients (natural or synthetic compounds that interfere with the absorption of nutrients) and issues with bioavailability. Developing a full understanding of what’s going on will take a number of years, and it will likely be more complex that the current theories – research will continue to support the evidence base and grow our knowledge.

Given this you may be a little worried if you are currently feeding your dog a grain-free diet. Firstly, don’t panic: as we’ve seen, this is still under investigation, and the actual number of cases is fairly rare in the grand scheme of things – although this does not mitigate the concerns that we need to follow up on to investigate to avoid further issues. Some recommended suggestions may in time turn out to be unnecessary precautions, once we have more evidence.

The limited evidence we currently have access to could suggest that the potential cardiac risks may be greater than benefits suggested by feeding a grain-free diet at present. Despite the uncertainty, is it is reasonable to be cautious with diets which are grain-free or that contain legumes in the top ingredients. Ingredients are listed order of predominance by weight, research has provided information on the effect of different diets and ingredients on taurine and other amino acids in dogs however, although we still don’t know the exact link between DCM and grain-free diets reassessment wouldn’t be unwise.

There are no proven health benefits to grain-free diets, other than in very rare and specific cases. Even with the research being in its infancy with regards to the potential risks, it is not unreasonable to exercise caution with these diets, especially if you have a dog whose breed has been shown in studies to be predisposed to experiencing diet-associated DCM. So far this includes Irish wolfhounds, Golden retrievers, American Cocker spaniels, Newfoundlands, St. Bernards.

It’s important to remain skeptical about the exact link between these grain-free diets and DCM, and to reserve judgement until we have more evidence. It is still early days in the research, and we shouldn’t run before we can walk. Grain-free popularity has grown massively but cases of dietary related DCM remain fairly low.

Thankfully in a very short period of time we are getting more and more research investigating the link between certain grain-free diets and their effect on cardiovascular health in some dogs – every study that comes out allows us to add one more piece to a puzzle. Additional research is needed to piece together the full picture to establish the association between diet (specifically grain-free) and DCM.

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