This is a great example of the unintended consequences that can result from making decisions based on scientific conjecture and preliminary hypotheses. In this case, the hypothesis was never a good one. If you are a pet owner, you may have noticed the recent trend toward grain-free dog or cat food. The justification for this trend is the notion that since dogs are essentially wolves, and wolves are pure carnivores, then we should not be feeding our dogs grains. This is basically the paleo diet for dogs.

It should be noted, however, that many carnivores do need to get some plant matter in their diet. They may get this from the stomachs of the herbivores they eat. Wolves will also occasionally eat berries as a minor supplement to their diet. But sure, wolves don’t generally eat grains. But that is not the problematic premise here.

The problem with the grain-free diet claim is that while modern dogs are closely related to wolves, they are not wild wolves. They evolutionarily split from wild wolves 15-40,000 years ago. Over that time their diet has shifted significantly. They no longer hunt in packs, but live off the scraps of human civilization. And they have adapted.

So the grain-free theory is flawed, and we should not base dietary recommendations on theory alone anyway, but actually gather evidence to test those theories. Perhaps we already have, in an unintended ecological experiment. In 2018 the FDA noticed a spike in reported cases of dilated cardiomyopathy (DCM) in dogs. Previous years had 1-3 reported cases per year, in 2018 there were 320, and 2019 is on track to exceed this. This is still a small number compared to the millions of pet dogs in the US, but is likely massive underreporting. There is also likely some reporting bias here – one article on social media might explain the spike, rather than a true increase. But the FDA had to investigate the increase to see if it were real and what the cause might be.

What they found was that 91% of the reported cases involved dogs who were being fed a grain-free diet. These dog food formulas contain peas, lentils, or potatoes instead of corn and wheat to mix with the animal protein. DCM is a known vulnerability in some large breeds, and these breeds were represented in the reported cases. The average age of death from DCM in these cases was 6.6 years.

Right now vets are tracking several categories of DCM. First, they are seeing DCM in dogs with diets other than grain free, including boutique diets and those with exotic ingredients. This has resulted in the term BEG to designate the at risk diets. Further, they are seeing DCM in dogs eating a BEG diet in genetically at-risk breeds, and breeds not normally at risk of DCM. Finally, there are cases of DCM in which taurine levels are low and those that are normal.

Taurine is an amino acid important for heart function. The idea is that the BEG diets are low in taurine, resulting in DCM. However, most of the cases currently being seen do not have low measured taurine levels. So supplementing taurine may not rescue these BEG diets from causing harm. Further, even when measured taurine levels are normal, dogs may benefit from switching to a traditional diet with proven ingredients.

So – what does all this mean? We don’t know yet. There may be more than one mechanism at work here, depending on the breed and the taurine levels. The one variable that is most consistent is the BEG diet, and the one intervention that seems to help is switching off this diet to one with traditional ingredients. Vets also warn against homemade and raw diets. Just give your dog traditional dog food from a proven manufacturer.

This was an entirely unforced error. Dog food formulas have been tested and were evidence-based, safe and healthy for dogs. However, trying to capitalize on the “clean eating” nonsense, some pet food manufacturers and pet stores decided to ride the trend. So they promoted an untested product based on dubious science and likely caused completely unnecessary health problems.

We still need to do more research to confirm the association and the cause of the apparent increase in DCM. It’s still early on in the phenomenon. For now the best advice is to simply feed your pets traditional products with tested ingredients. Don’t believe the hype, which at best is a waste of money, and at worst might do harm to your pets.