Unfortunately, Brent, courses in "nutrition" are electives for veterinarians. I have done tons of research on my own due to the loss of 3 pets because of the recalls 7 years ago. I happen to be good friends with a veterinarian who is continually studying and going to seminars. At a recent nutrition seminar, the discussion was regarding the numbers of American dog foods that actually use ingredients from China. Every pet food recall there has been has been linked to tainted ingredients from China.
The primary problem with commercial dog foods is the amount of corn included in the food. Besides the fact that most commercial corn is now genetically modified, dogs cannot digest corn. Period. The cheapest brands all contain at least 33% corn. The cheaper the food you feed, the more poop you're going to be cleaning up and the less healthy your dog will be. Giving your dog any commercial food sold at a grocery store isn't much different than feeding your children potato chips for dinner every night.
Shortly after that recall when I lost my 3 dogs, I began feeding a raw food that was biologically appropriate for dogs. Within 2 weeks, I saw healthier coats, brighter eyes, more energy and better focus in training. Feeding straight raw can be prohibitively expense - for my danes, it was costing me $50 per week per dog. It's also difficult to transition some dogs to it.
The biggest drawback to commercial foods is protein. If the food you are feeding lists "chicken by-products" as the first "meat" ingredient, your dog is not getting protein from it. By-products can include feet, beaks and feathers. If you can supplement your dog with meat and eggs from your table (or your farm) preferably raw but even cooked is better than nothing, you're dog will be much healthier than a straight dry food diet.