Superfoods are everywhere these days. Considered nutritionally dense and beneficial to your overall health, these so-called superfoods include plant-based foods, fish, seeds, nuts and berries. The American Heart Association says that there are no standard criteria or scientifically approved list of superfoods, but they are generally rich in vitamins and nutrients. So, do they really work? I tried four of them—kale, blueberries, quinoa and Greek yogurt—for four weeks to see what effect they had on me.