3 Ways. One, they substitute for foods that have high saturated fat and trans fat contents—these raise cholesterol levels. Two, they are high in soluble fiber, which lowers cholesterol. And three, they are high in phytosterols, which lower cholesterol.
Are there other reasons? Probably—vitamin E content, perhaps; protein metabolism; hormonal regulation. But it’s enough to know that nuts appear to be one of the few foods with actual medical effects.
In September 2003, the FDA announced that 1.5 ounces of nuts daily “may reduce the risk of heart disease.” So 34 almonds, 18 walnuts, plus pine nuts, pistachios, pecans, hazelnuts and even peanuts–and 1.5 ounces is more than is needed to lower cholesterol.