A safe place to. start in considering canine nutrition is first to determine whether dogs are genetically disposed to need certain diets. This approach will automatically filter out some of the current diet trends and marketing hype associated with these “diets".
Based on metabolism and nutrition, many consider the dog to be an omnivore. However, the dog is not simply an omnivore. More like the cat and less like other omnivores, the dog can only produce bile acid with taurine. Dog's digestive processes cannot produce vitamin D, which it obtains from animal flesh. Also more like the cat, the dog requires arginine to maintain its nitrogen balance. These nutritional requirements place the dog part-way between carnivores and omnivores. (https://en.m.wikipedia.org/wiki/Dog)
Additionally, dogs display an increased tolerance for starch and grains relative to their distant “cousin” - the wolf.
Given the dietary requirements and tolerances outlined above, a balanced diets consisting of high-quality protein and grains will be best for your dog. The trick is finding a dog food containing the required ingredients. One challenged with internet searching that yield dog food producer links that appear to be valid scientific content or provide a break down of the ingredients in the subject dog food.
Here are a couple things to take into account. The quality of the ingredients needs to be closely analyzed. Protein is good example.
Look for high quality protein, preferably a protein meal vs real protein. The act of producing the meal results in highly concentrated protein ingredient. The rendering process effectively removes water from the protein source and results in a cooked product. The resulting cooked product is effectively a protein powder or meal. The protein concentration can be as much as 3 - 3.5 times greater raw protein. It's best to find food with lean protein meal - chicken is usually a great choice.
Given dogs genetic digestive composition, it's important to find a food that also contains high quality grains, fruits and vegetables. The overall composition will ensure your dog has a balanced meal and gets all it’s nutritional requirements. Brown rice is better then white rice for instance.
Try also to avoid the latest fad. While reviewing and researching for this blog, internet searches continued to yield “total” grain hits. My feeling is that grain is “in” currently. While high quality grain is part of a high quality diet, it does not account for the specific diet needs of dogs.
Best to do your homework, seek guidance from informed and reasonable sources.