Hazelnuts contain nearly 91 percent monounsaturated fat and less than 4 percent saturated fat. Over 30 tree nut studies indicate this high level of monounsaturated fat is likely responsible for a reduction in both total blood and LDL cholesterol levels when hazelnuts are consumed as part of a low saturated fat diet. It also contributes significant amounts of protein, fiber, iron, phosphorus, vitamins B1, B2, C, and E, folate and many other essential nutrients. Replacing a less nutrient-dense snack with heart-healthy and flavorful hazelnuts has many health benefits.