If we look at any other animal, they produce fats on their own without eating much fat... look at whales for instance, or grass fed cows, free range chicken and their eggs etc.
If we get the very few things that we need, we should not have to supplement at all... maybe vitamin C, but I do not know about that now.
Water, salt, soda, Iodine is all in kelp and water... and I can tell you from my experience at christmas time that the sun is a whole different feeling in an iodized body... I turned brown while everyone else was slathering on the sun screen and ducking under towels, blankets beach umbrellas...
I think the healthy fats and oils have become so important to us, because we are so out of whack with bad fats, oils, halides, that our bodies are unable to make it for themselves as they should.
As an aside, even with all of the kelp I have been ingesting, I put some Lugol's on a couple of moles yesterday morning and the Iodine was soaked in before I went to bed last night. Makes me wonder how far gone Iodine was from my system as I have been eating kelp, dulse, etc. for over a year now... and getting better slowly all the time.