I was looking at my youngest this morning and thinking about this thread. All of my kids really. I really do increasingly believe that when kids are difficult about food right from birth that it needs to be considered that what we think of as "healthy" isn't healthy for that child.
We essentially poisoned our eldest child with healthy food. Slowly, carefully, gently, respectfully, without ever turning it into a power struggle we taught her to eat food that was actively harming her, because we thought we knew that broccoli, avocados, tomatoes and all manner if other food was good for her.
My youngest child has never eaten a normal diet in her life. Not ever. First third exclusively breast fed (which made her sick as a dog until I changed my diet at 10 months), second year she pretty much ate chicken, lamb, ghee, rice products and cucumber. Third year he's expanded her diet a tiny bit. And she's my most normally developing child (in terms of not having developmental delays, giftedness she has in spades). Given the full scale developmental regression we get from diet error I am sure the two things are related