What are grain free foods?
In recent years there has been a trend in human nutrition towards low carbohydrate/grain free/gluten free diets and the pet food industry has tried to follow. Grain free pet diets do not contain cereals such as wheat, corn, rice and oats. However, being grain free does not mean they are low carbohydrate as the vegetables in the mix contain carbohydrates. Often vegetables such as potatoes, sweet potatoes, peas and lentils are used to replace the grain. Dog can digest carbohydrates well, but like us, can survive without them. Dogs became domesticated about 15,000 years ago and their metabolisms are now quite different to that of their ancestors.
What is taurine?
Taurine is an amino sulfonic acid, but is one of the few amino acids that are not used as building blocks of complex proteins. Despite this, it is one of the most abundant amino acids in the brain, eyes and muscles, such as the heart. Taurine is only found in animal tissues and was first identified in the early 20th century in the bile of a bull, hence the name related to Taurus. The metabolism of many mammals can manufacture taurine from other molecules, but receive most of their taurine from their diet. Cats cannot make their own taurine and hence they are obligate carnivores and cannot survive without animal protein. Cats deficient in taurine develop a range of issues including heart disease and blindness. We know that taurine deficiency in humans and animals is linked to dilated cardiomyopathy.
What is dilated cardiomyopathy?
Dilated cardiomyopathy (DCM) is a disease that affects the heart muscle and leads to heart failure. As DCM develops the heart enlarges and the heart muscle becomes stretched and floppy; and therefore, less efficient at its job of generating blood pressure as it pumps blood around the body and lungs.
As with many diseases, there is a silent phase of the disease when the heart has reduced efficiency but no symptoms are present. With time, symptoms of heart disease develop; these include lethargy, weight loss, coughing, laboured breathing and collapse. Investigation of heart issues can include a clinical examination, blood tests, ECGs, x-rays of the chest and ultrasound of the heart. Treatment can be started to improve the heart function and slow the progression of the disease and associated symptoms.
It is most commonly caused by genetic factors and typically seen in larger breeds such as Dobermans, Boxers, Great Danes and German Shepherds. Hence when the disease appeared in atypical breeds such as Golden Retrievers the researchers took a closer look.
Study data
In July 2018 the U.S. Food and Drug Administration (FDA) issued a statement on a potential connection between diets and canine heart disease after they had reports of DCM in unusual breeds such as Retrievers, Whippets, Miniature Schnauzers and crossbreeds. Some, but not all, of the reported cases had been diagnosed with low taurine levels in their blood.
A study published in December 2018 by the University of California looked at a population of 76 Golden Retrievers, 24 of which had dilated cardiomyopathy and documented taurine deficiency. 23 of the 24 dogs with heart disease were being fed diets that we either grain free, legume-rich (peas and lentils), or a combination of both. The affected dogs were prescribed a diet change with taurine supplementation and all but one of the dogs improved.
So, is grain free food to blame?
It is still not clear whether the link between heart disease and diet is solely related to taurine levels or not, but it is likely affected by many factors. It may be that some of the ingredients in grain free diets are interacting with each other and reducing the availability of taurine from the diet. As dogs are able to produce their own taurine it may be that some of the ingredients are interrupting this process or other components of the metabolic pathway are missing. The most important thing in nutrition is balance and pet nutrition is a huge area of research and development. Hopefully more data will be collected and the link can be identified so that we can avoid problems in the future.
We all want the best for our pets, so when choosing a diet for your pet I recommend reading these guidelines written by the World Small Animal Veterinary Association and choosing a diet produced by one of the members of the Pet Food Manufacturers Association. If your dog has already been diagnosed with DCM then please discuss their diet with your vet, especially if you are considering switching food.
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