Walnuts are an energy food, packed with minerals such as phosphorous, potassium, magnesium, calcium, zinc, and selenium. They are rich in Omega-3 fatty acids, especially alpha-linolenic acid, which helps to keep the nervous and cardiovascular systems healthy. They are also full of group B vitamins and vitamin E, which protects tissues against oxidative stress, and tryptophan, a precursor of serotonin (the feel-good hormone).