When I was a kid my mother read in one of her magazines that children should be encouraged to eat the white part of the orange peel. According to the article, this usually-discarded part of the fruit is high in calcium.
A dutiful child, for years I ate that part of the peel, scraping it from the outer rind with my teeth. When I grew up I saw no documentation for its nutritional content, so I generally avoid it now. But what I don't understand is the constant admonition of every food writer that the white part of the peel be avoided because of its "bitter" taste. I've tasted it many a time, and bitter is not a word I would use. It's very bland, and has a texture that would certainly detract from its use in cooking, but there is nothing bitter about it.
My conclusion is that everybody says it's bitter because they've been told it's bitter. If they actually tasted it, they would stop saying that. They might find any number of reasons to tell us not to use this part of the orange, but bitterness would not be among them.
I wonder if it's true that it is high in calcium. I can't help but think it is. It's white as milk, and soft as beans. It has a blandness that makes one think of high-calcium foods. It is part of an extremely nutritious fruit. I'd like to think that it is worth doing something with, if only eating as is after peeling and sectioning an orange. I wouldn't use it when candying the peel, or when grating it, but I wouldn't be afraid of it. It isn't a bit bitter, and it may actually be good for you.