Walnuts are high in monounsaturated and polyunsaturated fats and omega-3 fatty acids, with 2.5 grams per ounce, making them a healthy source of manganese, copper, magnesium, phosphorus, vitamin B6, and iron. They are also high in monounsaturated and polyunsaturated fats and omega-3 fatty acids. Walnuts include several plant chemicals and nutrients that may help reduce inflammation, which is a major cause of many chronic diseases.