Here's what The Mayo Clinic says about nuts. They have:
Unsaturated fats - helps lower cholesterol
Omega-3 fatty acids - good fats for healthy hearts
Fiber - helps lower cholesterol and helps you feel full
Vitamin E - helps stop the development of plaques in your arteries
Plant sterols - helps lower cholesterol
L-arginine - helps improve health of artery walls making them more flexible and less prone to blood cloths that restrict blood flow
They are also cholesterol free, full of folate, antioxidants, calcium, magnesium, and potassium.