Omega-3s are fatty acids that can be found in anchovies, walnuts, chia, sardines, and more. And we’ve been told they are supposed to make your heart and brain stronger. A multimillion dollar supplement industry has been built around making sure humans get their share of Omega-3s. But Paul Greenberg spent a year eating a fish-focused diet for his new book and found not only is this better for eaters, it’s better for the planet.