One of the first nutrition books that I got out from the library (I think it was this one by the CSIRO) suggested that rather than tell kids that food was "good for you" or just "healthy"you should try and link the food to a specific outcome. If I remember rightly it used the terrible stereotypes that boys will want to hear that food will make them run fast and girls will want to hear that food will make their hair shiny.
I experimented the very next day by telling Leo that if we put sesame seeds in his porridge they will make him strong and it was a huge success. Most days Leo will ask for porridge with magic seeds to make him strong.
However, when I tried it with carrots (carrots will make you run very fast) it didn't work at all. In fact, every time I've tried it with any other food, it's totally failed.
So while I would totally recommend this tactic of hyping up the nutritional benefits of healthy food, I would definitely say save it for the one food that they otherwise won't eat!!