The main culprit in these diets appears to be the pea protein including lentils and chickpeas. In order to make a food grain free some companies increased the use of these legumes to bind the food together. The problem with this is that dogs are carnivores and require more meat as their protein source because plant proteins do not contain taurine which is an amino acid that the heart muscle needs to function. Not all dog food companies add taurine to their diets although since this study came out more are doing it now.

Your vet is right that not all pet food companies balance food properly; many do not even have a nutritionist on staff and do not do their own feeding trials so sometimes the ingredient list looks good but micronutrients are missing. If you like to feed a more natural food I do like Fromm which has been around a long time (but avoid the lamb and lentil diet) and Purina Pro Plan has some good diets without byproducts but you need to look at the ingredients list. I like the Sensitive Skin and Stomach salmon and rice diet and have fed that to my own dogs. I tend to change brands and formulas to give a variety.

Some dogs are allergic to corn and wheat but are able to eat rice/barley/oats/quinoa and if you really want grain free consider one with potatoes which I think is safer than the lentil based diets. Some peas in a diet may be okay but too many seems to be the problem. They are still trying to investigate the link between the pea-based diets and actual heart failure/DCM since not all dogs eating these diets go into heart failure. I have personally had a few clients with dogs eating these foods develop DCM and die at very young ages which is sad if it was preventable. My dogs used to eat grain free and  I stopped feeding any diets with high pea protein just to be on the safe side.

Pam