While fat provides 73 percent to 90 percent of the calories in nuts, they're mostly the heart-healthy monounsaturated and polyunsaturated types. English and black walnuts in particular are high in protein, fiber, magnesium, vitamin E, and potassium. In the Harvard-sponsored Nurses' Health Study involving over 85,000 women, eating just 1 ounce of nuts more than five times a week was associated with a significantly lower risk of coronary heart disease. Walnuts are also one of the only common nut varieties containing alpha-linolenic acid, a type of omega-3 fatty acid typically lacking in the Western diet. Low reserves of linolenic acid can result in a range of symptoms, from dry skin to high blood pressure. Toasting nuts over direct, high heat can destroy fragile omega-3 fatty acids, so enjoy them raw or just slightly heated.