The natural form of a mineral is always the best choice, when available. The most biologically sound minerals available from whole foods, rather than in chemically processed synthetic forms, are the best option to put into your dog's body. If you are unable to give your dog a raw food diet and supplement with foods that are high in mineral content, food processed with chelated minerals might be an option for you and your dog. However, there is some controversy with chelated minerals and processed dog foods.
If your dog can consume a raw food diet or a whole food diet, there is no reason for your dog to require additional supplements because they will obtain all the nutrients they need from their diet. Trace minerals your dog needs will come from fresh whole foods and vegetables. Finding sources of minerals to add to your dog's processed food is not difficult through raw meats, raw pumpkin seeds, spinach, which is rich in magnesium and iron, along with pineapple and other fresh fruits and vegetables. Trace minerals are added to processed dog food as well as other vitamins and nutrients because the processing of organic materials often takes nutrients away, causing manufacturers to add nutrients back in for proper nutrition for your dog.