Pet owners trying to keep their dogs on a healthy, grain-free diet might actually be putting them at risk, according to the US Food and Drug Administration.

An alert was issued by the FDA on July 12 after they received reports of canine dilated cardiomyopathy (DCM) in dogs eating pet foods that contained peas, lentils, potatoes and other legume seeds as the main ingredients.

DCM is a heart muscle disease that results in an enlarged heart. As the heart enlarges, it becomes harder for it to pump and its valves may leak, resulting in fluid build-up in the chest and abdomen. DCM often results in congestive heart failure.

There is currently no known cause for DCM, but researchers have often thought that there was a genetic component. The disease is more common in larger breeds of dogs, such as Great Danes, Boxers and Saint Bernards. However, the FDA has received reports of DCM in dog breeds not typically genetically prone to this disease.

The cases of DCM reported to the FDA included dogs on diets that included potatoes and legumes as their primary sources of nutrition. Dogs eating high levels of these foods are typically on diets labeled as "grain-free."

The FDA has not yet determined how these ingredients are linked to the DCM cases. An investigation on the potential association between grain free diets and DCM is currently underway at the FDA's center for Veterinary Medicine and the Veterinary Laboratory Investigation and Response Network.