Runner's World has put together an article trying to quantify the portion of one's diet that should consist of highly processed foods--not just the classic white flour, refined sugar, and the like, but also packaged snacks, energy gels, and even protein bars.
Now wait? Protein bars? Yes, and here's why. When protein is extracted from other sources--whether from whey/dairy, peas, beans, or other sources--what is done is to take the protein with as little of the "other stuff" as possible. Now those who like protein bars would say it's a good thing that they're reducing the amount of carbohydrates in their food (advocates of the Mediterranean diet might disagree), but the kicker here is what else is disposed of with the carbohydrates.
You see, bran is just a long chain carbohydrate, so it stands to reason that as you get rid of carbs, you get rid of fiber and all the cool nutrients that are in that fiber--vitamins and minerals especially, as the bran and such is where the precursors to chlorophyll are stored for when the seed sprouts into a plant. And so even when the "end result" in terms of "macros" seems right, many of these refined protein sources are in fact fairly depleted foods.
Why is this significant? It goes back to something I remember thinking when talking with friends who were excellent womens' distance runners; they were going to skinless chicken and turkey breast for protein, and then wondered why their red blood cells were in effect turning pink. Poultry breast is an excellent source of protein, but does not have the iron of beef, pork, or even beans or poultry legs.
And so I wonder if a lot of our "healthy diet advice" is really leading people to adopt a fairly "depleted" diet, and is thus actually making things worse for a lot of otherwise healthy-eating people. It's one thing to ease off the SAD, but if we simply exchange high carbohydrate refined foods for high protein refined foods, we aren't doing ourselves many favors.