Somehow natural foods and diets went from base products found in gardens and pastures, to packages being delivered from large mills. A Natural diet is a Raw Diet. If the products the processed manufacturers were producing was a natural diet, why would they need to supplement with calcium and other mineralized compounds?
A raw diet demands variability. Variability is not only good for the dog, it is good for the owner. The variability should include the vitamin sources as well as protein sources. Poultry as a base with meaty beef bones to chew on, and liberal addition of vegetables and some fruit provides a lot of room for variability. Grains are not a requirement but can be added on occasion. A little whole fish, or fish oil, is always good as well.