Grain free diets have gotten a lot of publicity in the past few years regarding a connection to dilated cardiomyopathy and pet owners are understandably confused as to whether they should steer clear or not, as the research into this concerning finding continues.
However, given the ongoing investigations into grain free diets, we mustn’t forget that cats are still also susceptible to nutritional dilated cardiomyopathy. Many of the studies are based around dogs, due to the higher caseload and sample size to draw on – but this doesn’t mean we should dismiss their findings.
Today’s blog is about what can we learn from the currently available studies in dogs and cases in cats, what we still don’t know about feline DCM, why there aren’t as many documented cases in cats related to grain free diets, and if we should be avoiding grain free diets in cats.
So what is DCM?
Dilated Cardiomyopathy is a disease of the heart muscle characterized by fluid build-up in the body and clot formation in the arteries; the four chambers in the heart expand or ‘dilate’ which reduces the heart’s ability to pump correctly which causes fluid build-up in the body and affects the cat’s ability to breathe. DCM is well documented in cats; before 1987, it was an incredibly common disease in cats as the relationship between taurine deficiency and heart disease was unknown. It wasn’t until Pion et al (1987) discovered a deficiency in the amino acid taurine was a cause of dilated cardiomyopathy that it became a requirement for taurine to be present in all cat diets which is why the disease become as uncommon as it is today.
However, it is now making a comeback. Grain free diets have been implicated in the rising numbers of dilated cardiomyopathy – in both dogs and cats. In dogs, breeds not usually affected by DCM appear to be developing the condition, as well as unrelated dogs fed the same grain free diets in the household. In cats, there are fewer cases, but the concern is that it is not being as readily diagnosed and reported.
What can we learn from canine nDCM?
There are currently a number of ongoing studies, however many are aimed at dogs. The reason for this is it’s easier to identify in dogs as we have a much bigger sample size (1,100 cases in dogs). Some of the current thoughts around n-DCM and it’s connection to grain free diets can help shape our approach and knowledge of the condition in cats, despite their differing nutritional needs.
The studies relating to grain free diets have been looking at a number of lines of enquiry;
- Exotic meats such as kangaroo, crocodile, and/or bison usually included in grain free diets don’t have a comprehensive nutrient analysis compared to more commonly used meat proteins (chicken, beef) which begs the question if they provide adequate taurine or if it is in a bioavailable form. Many of the diets linked to DCM in dogs seemed to also have exotic protein sources. Given cats need taurine to be supplemented in their diet, it potentially could be an explanation as to why it is seen less readily in cats fed grain free diets compared to dogs – the supplements could have a masking effect.
- Dogs can synthesise taurine from cysteine & methionine therefore it is hypothesised that legumes interfere with this pathway, so rather than the diet being directly deficient in taurine the diet may be deficient in one or more co-factors in the synthesis of taurine or block the body’s ability to make use of taurine. This is still up for debate as dogs fed grain free diets didn’t all have deficiencies of taurine – many had excess or normal taurine levels.
- Vitamins B6, B12, folic acid & choline are methyl donors and should be at sufficient levels in the diet as they are also supportive of heart health. Many of these vitamins are found in red meat, so perhaps a deficiency of these vitamins could be related somehow to the exotic meat proteins and how the body processes it.
- Excess fibre from leguminous sources can impair the digestibility of protein. It’s commonly misunderstood that grain free diets are carb free when in fact they can be higher in carbohydrates than grain based diets, therefore this increases the fibre content of the diet and without digestibility studies, you can’t guarantee the bioavailability of nutrients isn’t impaired by the fibre.
- Troponin levels in dogs with DCM were extremely high, once on grain inclusive diets the levels normalised and dogs recovered; troponin is linked to causing damage to the heart muscle in rat models, so potentially an ingredient in the food causes in increase in this chemical which then causes damage to the heart rather than blocking taurine.
There are still many unknowns as to why dogs who have eaten grain free foods and have developed dilated cardiomyopathy and the research is ongoing, but these findings help us form a basis for ensuring safe and healthy diets for both cats and dogs. Given taurine is an essential amino acid to cats, and their diets are usually already supplemented with it appears to be somewhat protective, however there are other reasons that can explain the lack of cases seen in cats.
Why aren’t there many cases of cats?
The FDA investigation currently includes twenty cases of feline DCM linked to grain free diets, five of which died from the condition. The symptoms of DCM are difficulty breathing, poor appetite, weight loss, hindlimb weakness or paralysis, coughing or exercise intolerance. Looking over that list, you can already identify why it may be hard to spot a cat with DCM; symptoms like poor appetite, coughing or exercise intolerance may be easily missed, ignored or considered normal for cats. They are unlikely to trigger the pet owner to bring the cat into the vet and even if brought in for a visit, if there isn’t a heart murmur or some other physical sign of ill-health, the disease may be missed. As a veterinary professional, my other concern would be cats that die without a formal diagnosis – we may never know the true number of deaths as owners may be too distraught to investigate deaths or their pet’s illness, particularly if it was sudden in onset. Another reason we may not be seeing as many cases could be the taurine supplementation present in all cat food; in some canine cases, providing taurine supplements did help treat their condition, even though it isn’t an essential nutrient for dogs therefore this may be masking cases of grain free DCM in cats.
The good news
Majority of the cases studied in dogs made a full or partial recovery when the diet was changed to one including grains! This is unlikely to happen if the condition is unrelated to diet, and is of a genetic cause (as is more common in dogs). Of course, changing to a grain inclusive diet isn’t a cure, and your pet may still require medicine to manage the condition, however any improvement in the condition is positive.
So can I still feed my cat grain free food?
It is still your choice if you wish to feed your cat a grain free diet, however it is important to understand the risks. We know that feeding a complete and balanced grain inclusive diet is safe and not linked to developing dilated cardiomyopathy; grains are nutritious and beneficial to the diet, unlikely to be linked to allergies and are able to be digested effectively by cats, so there really isn’t any reason to exclude them from the diet. If your cat is currently on a grain free diet, I would recommend switching to a grain inclusive diet – its better to be safe rather than sorry. Don’t want to switch? Looking for a diet that doesn’t contain legumes and pulses in the top 10 ingredients is the current recommendation from the FDA, and if your cat has been or is currently on a grain free diet, it’s strongly recommended you have an echocardiogram performed by a Veterinary Cardiologist every 6-12 months to catch any signs of disease. And if your cat has been diagnosed with DCM after eating a grain free diet, make a report via the FDA website with the help of your vet – this helps both further the research in cats, crack the grain-free code and develop new treatment options for your pet and others.
Does your cat eat a grain free diet? Are you staying up to date with the latest research on the connection between grain free diets and DCM? Let us know your thoughts below!
References
https://onlinelibrary.wiley.com/doi/10.1111/jvim.16075