Soybeans and health

In On Food and Cooking, Harold McGee describes the soybean as

“exceptionally nutritious, with double the protein content of other legumes, a near ideal balance of amino acids, a rich endowment of oil, and a number of minor constituents that may contribute to long-term health.” page 493.

Soybeans contain storage forms of isoflavones. These are phenolic compounds are liberated by intestinal bacteria as phytoestrogens, a form that resembles the hormone estrogen. Boiled whole beans contain the most isoflavones. Some research suggests that they may slow bone loss, prostate cancer, and heart disease, but due to their hormone-like effects on the body, soybeans can worsen pre-existing breast cancer. This process is not completely understood.

Soy beans are also a rich source of saponins, which are soap-like defensive compounds that are both, water- and fat-soluble. Soy saponins bind cholesterol so that the body can’t absorb it efficiently. Furthermore, soybeans have phytosterols, chemical relatives of cholesterol, which also interfere with cholesterol absorbtion.

For all their goodness, soybeans are at the same time, unappealing. They contain abundant antinutritional factors, fiber, and oligosaccharides. They contain negligible amounts of starch. Their texture tends to remain firm. To make them more appealing, the Chinese and others have developed ways to alter their taste, such as via extraction of the protein and fermentation.