Soy products may also lower blood cholesterol levels. An analysis of 38 studies in which soy protein replaced animal protein in people's diets found that eating an average of 47 grams (about 10 ounces) of soy protein per day lowered levels of total cholesterol by about 9percent, LDL cholesterol by 13percent, and triglycerides by 11percent. The substitution of unsaturated for saturated fat (38percent of the calories in soybeans come from fat, mostly unsaturated) may account for some of this benefit.

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But soy also contains phytochemicals (plant chemicals)--isoflavones, in particular--that may contribute to the cholesterol-lowering effect. Isoflavones are estrogenlike compounds present in soy foods such astofu and soy milk; estrogen lowers LDL cholesterol and boosts HDL cholesterol levels.