A review study, published in Nutrition Reviews discusses numerous mechanisms through which soybeans exert their protective effects against heart disease, cancer, and osteoporosis.
Most of the research on soybeans' benefits has focused on the role isoflavones play in disease prevention or treatment, but studies show that soy proteins also contribute to soyfoods' protective actions against cardiovascular disease, osteoporosis, and cancer.
Soy isoflavones have been shown to increase the resistance of LDL cholesterol to oxidation, improve blood vessel flexibility (arterial compliance) in menopausal and peri-menopausal women, and help lower post-menopausal women's risk of developing osteoporosis by helping to maintain a better balance between bone resorption and formation.
Isolated soy protein and soy peptides (amino acid components) have also been shown to help prevent cardiovascular disease by stimulating the expression of LDL-receptors and the break down of LDL in cultured liver cells. Studies, however, indicate that isoflavone-rich soy proteins are much more effective at lowering LDL-cholesterol than isoflavone-depleted proteins.
A diet high in soy foods has been associated with reduced risk of several types of cancer, such as breast, endometrial and prostate. Soy isoflavones' antioxidant properties likely contribute to soy foods' anti-cancer effects by reducing free radical damage to fats (lipid peroxidation) and DNA. Soy isoflavones may also induce Phase II liver enzymes (such as glutathione-s-transferase and quinone reductase), which help the body eliminate the toxic byproducts (aromatic hydrocarbons) produced when meats are charbroiled.
Soy peptides and protein isolates also have antioxidant properties that can contribute to soyfoods' anti-cancer effects. In addition, a soy protein isolate has been shown to interfere with the circulation of bile acids, which are known to play a critical role in colon and liver tumor development.
Scientists may need to isolate soy's isoflavones and protein components to better study how this amazing legume provides its many benefits, but our goal is to receive them all. Fortunately, it's easy to do so I just enjoy foods made from whole soybeans.