It is disappointing as I look through retail pet supply stores and view their product line of supplements and see the shelves dominated by what is actually high fat products.
There are fortifications of flax seed, soy oil, corn oil, and safflower oil and many of those products are classified as fats that heal, and they do to a certain degree. The problem with using those products is that many issues are sub-clinical meaning there are no symptoms of those problem.
A good example is a copper deficiency which may have some evidence by virtue of a slightly dull hair coat or a little dullness to the overall look of the hair. A diet supplemented by some of these oils listed might darken the coat and give shine to it but it does not address the root cause of the problem.
Copper is a valuable part of a dog's diet. It helps maintain an immune system response, aids in vitamin utilization, stimulates blood production, and maintains proper enzyme production. This is so key to a dog's health and liveliness. It can virtually keep a dog alive.
I recently went to a major pet store chain and there was about a dozen dietary supplements and only one was a true vitamin/mineral supplement. The rest were oil or fat based products which were being marketed in a way to make the customer believe he was taking care of the dietary needs of his or her pet. There is a large hole in the market.