The New York Times has a list of food myths, solicited from a variety of experts. The main takeaway is that all you really need to pay attention to when it comes to diet is Michael Pollan’s 2007 article on nutrition, in which he provides a simple suggestion:
Eat food. Not too much. Mostly plants.
Everything else seems to be subject to change based on the latest of the research and the fashions and hysteria of the day.
Update: More evidence that eating lots of red meat is really bad for you. My advice is to turn to fried chicken for refuge.