You might have seen the commercials. A dog food brand touts the health benefits of its product because of the high amount of protein in it and the fact that it's not filled with grain. Just as more human foods have become gluten-free, more dog foods have become "grain-free."

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In the last 10 years, people made the leap that grains in dog food are bad for their dogs, says Dr. John Faught with Firehouse Animal Health Center. And until last year, most veterinarians didn't really think there was a benefit, he says, but they also didn't think it was harmful.

Then dogs started being diagnosed with a heart condition — canine dilated cardiomyopathy — that typically happens to big dogs such as Great Danes and Dobermans, Faught says, except veterinarians were seeing it in little dogs like Chihuahuas. Of the 560 cases the FDA has recorded, 119 dogs died of this disease, the FDA reported in June.

"The only consistent thing was they all ate a boutique or grain-free diet," Faught says. "All protein is not good for any species. It doesn't give us the well-balanced diet we need of carbohydrates, proteins and fats."

The symptoms of canine dilated cardiomyopathy include cough, decreased energy, difficulty breathing and collapse.

This FDA study, which is the third such study in the last year, points out that when it came to the "boutique" foods, many of them didn't have traditional grains like corn or wheat, but they did have some other foods that might sound healthy but also might be part of the problem. The FDA specifically notes foods that had peas or lentils in them.

We don't exactly know why these types of dog foods could be having this effect, Faught says. "The challenge here is nobody has narrowed down the exact cause and effect," he says.

Staff members at the FDA are looking at some of the nutritional levels of the blood in the affected dogs and thinking that they might have too much of the amino acids cystine, methionine and taurine.

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The FDA's June report was different from the first two in that it named the dog food brands that the affected dogs were being fed and the number of cases:

Those brands were (in order of cases):

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

Rachael Ray Nutrish

Instead of following a fad or a TV commercial, Faught recommends talking to your veterinarian about your pet's specific needs in a food.

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There are some clues on the food wrapper that can help guide you when choosing what to feed your dog, Faught says. Look for AAFCO feeding trials noted on the label. That means the food has been tested by the Association of American Feed Control Officials.

Faught also recommends that if you're uncertain about your dog food, you can call the company and ask to speak to the nutritionist. If there isn't one, that is a red flag.

You can't always judge a dog food by price, he says. "You can spend a lot of money for crappy food or the other way," he says, but usually foods with higher-quality ingredients are going to cost more; "that's generally true," he says.

For vets, the recent FDA reports have them asking clients who suspect their dog has heart problems whether the dog is on a grain-free diet, and instead of not weighing in on whether it's OK to feed dogs this diet, they're now taking a position against it, Faught says.