One particularly healthy nut is the walnut. Walnuts contain alpha-linolenic acid, which is good for the heart. They also contain the plant compounds known as sterols, which block the absorption of cholesterol.
The almond is another healthy nut, capable of lowering bad cholesterol and raising good cholesterol. Almonds also have more calcium than any other nut. Their high fiber may help prevent colon cancer.
Pistachios have many of the same benefits as the other nuts, as well as the carotenoids lutein and zeanthin. These are known to help prevent macular degeneration, which is the leading cause of blindness for people 65 and older.