While recent research has confirmed that soy's isoflavones are not the agents responsible for its cholesterol-lowering effects, a study published in the Journal of Nutrition shows that soy protein does lower heart disease risk by increasing the size of LDL cholesterol particles. Small dense LDL is the most dangerous form of cholesterol, while large LDL, especially when accompanied by adequate supplies of HDL is considered much less risky.
In this study, conducted at the Jean Mayer USDA Human Nutrition Center on Aging at Tufts University, researchers found that people who ate diets high in soy protein significantly increased their LDL particle size compared to periods when they ate diets high in animal protein.
Study participants, all of whom had high cholesterol, were given four different diets, each for a period of six weeks: soy protein with no isoflavones, soy protein enriched with isoflavones, animal protein with no added isoflavones, and animal protein with added isoflavones.
While isoflavones had no effect, soy protein consumption resulted in a decrease in the amount of small dense LDL and an increase in larger LDL particles compared to animal protein¡ªa significantly less risky cholesterol profile.