Textured soy protein is made by forcing defatted soy flour through a machine called an extruder under conditions of such extreme heat and pressure that the very structure of the soy protein is changed.
Soy protein isolate (SPI) begins with defatted soybean meal, which is mixed with a caustic alkaline solution to remove the fiber, then [...]

Hexane is a colorless highly flammable liquid alkaline derived from petroleum and used as a solvent.
The main use of hexane is as a solvent to extract edible oils from seeds and vegetables such as soybeans, peanuts and corn.
Hexane residues of 21 ppm were discovered in soy meal commonly used to produce soy protein for infant [...]

More than 70 years of human, animal, and laboratory studies show that soyfoods are detrimental to thyroid health. The chief culprits are the plant hormones in soy known as phytoestrogens or isoflavones.
The United Kingdom’s Committee on Toxicology has identified several populations at special risk: infants on soy formula, vegans who use soy as their principal [...]

From the Weston A Price Foundation

High levels of phytic acid in soy reduce assimilation of calcium, magnesium, copper, iron and zinc. Phytic acid in soy is not neutralized by ordinary preparation methods such as soaking, sprouting and long, slow cooking. High phytate diets have caused growth problems in children.
Trypsin inhibitors in soy interfere with [...]

The people of China, Japan, and other countries in Asia eat very little soy. The soy industry’s own figures show that soy consumption in China, Indonesia, Korea, Japan, and Taiwan ranges from 9.3 to 36 grams of soy foods (not isolated soy protein) per day.  A cup of tofu contains 252 grams and soy milk [...]