 It is thus advised that vegan diets include a mineral source of calcium to ensure healthy functioning, and most commercial vegan formulas supplement calcium in the same manner as conventional dog food.Vitamin D is essential for proper calcium regulation and is important for bone mineralization, nerve function, immunity, and intracellular signalling.Dogs are able to synthesize and convert 7-dehydrocholesterol (provitamin form of vitamin D) to cholecalciferol (inactive form of vitamin D) following exposure to UV light from the sun.