Soy components vs. whole soy: are we betting our bones on a long shot?

Soybeans are a good source of bone-healthy nutrients. Epidemiological studies in Asia evaluating diets containing traditional whole soy foods show a positive association with bone mineral density and fracture protection. Smaller scale intervention studies in Western nations mainly feature isolated soy protein (SP) and purified or concentrated soy isoflavones (SI) rather than whole soy foods and they have produced inconsistent results. Consumption of SP does not alter calcium (Ca) retention even though urinary Ca excretion is less in diets with SP compared with proteins higher in sulfur-containing amino acids. SI, often consumed at higher concentrations than would be available in traditional Asian diets, are not yielding the type of incontrovertible evidence that might be expected in support of their benefit to bone health. This forces one to ask whether whole soy might provide a superior effect on bone.