Mystery of the Heart
What’s causing unusual cases of dilated cardiomyopathy in dogs? Dietary ingredients, lack of taurine are potential culprits, but the answer remains elusive
By Kim Campbell Thornton
Andrews McMeel Syndication
For several months, the United States Food and Drug Administration’s Center for Veterinary Medicine, in partnership with independent diagnostic laboratories and veterinary cardiologists and nutritionists, has been investigating reports of a trend that began at least two years ago: Some 150 or more dogs (and at least seven cats) that ate pet foods containing plant-based sources of protein among their main ingredients have developed dilated cardiomyopathy (DCM).
Canine DCM is a disease of the heart muscle that causes the heart to enlarge and decreases its ability to pump blood, often leading to congestive heart failure. It has a number of possible causes, including genetic predisposition, infection or toxins, and diet — in particular, a lack of taurine. Here’s what is known so far.
The reported cases of DCM are unusual because they are occurring in breeds such as golden and Labrador retrievers, whippets, a Shih Tzu, a bulldog, miniature schnauzers and mixed breeds, none of which are typically prone to the genetic form of the disease. (Breeds genetically predisposed to DCM include Doberman pinschers, Great Danes and boxers. Cases of DCM responsive to taurine supplementation have been reported in cocker spaniels.)
Reported cases are also unusual because many of the dogs consistently ate what are popularly described as “grain-free” foods, with high levels of legumes such as peas, beans and lentils; legume seeds (known as pulses); potatoes; or foods with exotic protein sources such as kangaroo.
Investigators have so far been unable to determine why these ingredients might be linked to cases of DCM. In some cases, dogs had not eaten any other food for months or years before exhibiting signs of DCM.
At least four dogs in reported cases had low blood levels of taurine, an amino acid that helps power “excitable” tissues such as the brain, skeletal muscles, retina and heart. Taurine deficiency is documented as a potential cause of DCM.
That said, in four other cases, the dogs had normal blood taurine levels. In some cases seen by cardiologists, though, dogs who were not taurine deficient improved with taurine supplementation and diet change, according to an article by veterinary nutritionist Lisa M. Freeman, a member of the clinical nutrition service at Cummings Veterinary Medical Center at Tufts University. It may be that individual dogs have different taurine requirements based on breed, size or some unknown factor.
The FDA notes that other factors could include nutritional composition of the main ingredients or how dogs process them, sourcing or processing of primary ingredients, and amount of the ingredients used. Various proteins, including meat proteins, have different nutritional profiles and digestibility. Studies have found that certain large dogs fed commercially available complete and balanced lamb and rice diets may have increased risk of developing taurine deficiency-induced DCM. A 2007 study found that giant dogs took in less taurine than small dogs, possibly because of a slower metabolic rate.
Because it is not yet understood how or if grain-free diets are linked to cases of DCM, the FDA recommends consulting a pet’s veterinarian about whether to change a diet. Dogs or cats with signs of DCM or other heart conditions — such as low energy, cough, difficulty breathing and collapse — should be seen by a veterinarian immediately. Guidelines released by veterinary cardiologists and nutritionists advise testing blood taurine levels of dogs diagnosed with DCM and changing the diet based on consultation with a veterinary cardiologist. A taurine supplement may be recommended. Improvement after dietary change and supplementation can take up to six months. Report possible dietary cases of DCM to the FDA.