I too am confused by conflicting nutritional advice. A couple of decades ago margarine was better than butter. Today margarine is bad!
Michael Pollan’s “In Defense of Food” questions this nutritionism that has conditioned us. My favorite piece from the book is “when the vitamins were isolated a few decades later, scientists thought, okay, now we really understand food and what the body needs for its health; and today it’s the polyphenols and carotenoids that seem to have completed the picture. But who knows what else is going on in the deep soul of a carrot? The good news is that, to the carrot eater, it doesn’t matter.”
My verdict: Backed with 23 pages of references/sources, Michael Pollan knows what he is talking about.