Nutrition advice is a carnival of health-fad snake-oil hawkers, protein-guzzling muscle men, garbage-food peddlers, and marketing hypnotists. Mark Bittman is here to escort us away from those distractions, reminding us of the simple tenets of healthy eating along the way. In his new book, How to Eat, he and co-author David Katz, MD, do just that.  We…