Walnuts are the only nuts that provide a significant amount of the essential plant-based omega-3 fatty acid ALA (2.5 grams per 1-ounce serving), and also contain protein (4 grams) and fiber (2 grams). A systematic review from Harvard also found that a diet supplemented with anywhere from 5 to 24% of calories from walnuts resulted in a significantly greater decrease in total cholesterol. We love walnuts in everything from energy bars and breakfast bowls to soups, salads and pasta.