Grain-free pet food as well as those loaded with healthy-sounding ingredients like peas, lentils, potatoes or sweet potatoes may not be as good for your dog as you think.

That’s the message from the U.S. Food and Drug Administration (FDA), which is investigating a potential link between certain diets and a rare but often deadly heart condition called Canine Dilated Cardiomyopathy, or DCM, a disease of a dog’s heart muscle that can lead to a buildup of fluid in the chest and abdomen, and congestive heart failure.

The investigation follows an uptick in the number of DCM cases reported in recent years.

Health officials have identified 16 dog food brands that may be connected to canine heart disease, including Acana, Zignature, Taste of the Wild, 4Health, Earthborn Holistic, Blue Buffalo, Nature’s Domain, Fromm, Merrick, California Natural, Natural Balance, Orijen, Nature’s Variety, NutriSource, Nutro and Rachael Ray Nutrish.

Many of these products are available online or in stores in Canada and two of the brands on the list, Acana and Orijen, are manufactured in both Canada and the U.S. by Champion Petfoods.

Most of the products were dry dog food formulations, but raw, semi-moist and wet foods were also reported. In most cases (over 90 per cent), the dog had been regularly eating a mostly grain-free product. And in 93 per cent of the cases, the pet food was formulated with peas and/or lentils. A far smaller number (42 per cent) contained potatoes.

The FDA is still unsure as to why there may be a connection between these foods and canine heart risk — nor have there been any product recalls — but advises people to consult their veterinarian for a balanced diet suited for their pet’s needs.

“Our ongoing work in this area is a top priority, and as our investigation unfolds and we learn more about this issue, we will make additional updates to the public,” Steven M. Solomon, director of the FDA’s Center for Veterinary Medicine said in an FDA press release.

“In the meantime, because we have not yet determined the nature of this potential link, we continue to encourage consumers to work closely with their veterinarians, who may consult a board-certified veterinary nutritionist, to select the best diet for their pets’ needs.”

Dr. Ted Morris, a veterinarian with the Toronto-based Bloor Animal Hospital, told the CBC that he believes the current popularity of grain-free food stems from the fact that people often want their dogs to eat like they do.

“A lot of people trends will end up moving over into the animal world,” he said. “So all the low-carb diets… [People think] ‘Oh if it’s good for me, it’s got to be good for my dog.'”

Further, the nutrient content of pet food isn’t federally regulated in Canada, veterinarian and researcher Dr. Sarah Dodd, told the CBC. The only regulation in this country around pet food relates to labelling, she said, as opposed to rules around nutrient content.

“You could put anything in a bag and call it dog food, as long as your manufacturing and contact details are on the bag,” she said, adding that while industry regulations for the nutrition of pet food in Canada is voluntary, pet food sold in the U.S. must meet American standards.