Soybean Taboo was noticeable to average people in the American sphere, no later than the early 1970s. (This will likely prove to be the case in Europe, too.) Especially the processed protein component (aka TVP Textured Vegetable Protein) that becomes available (and even a disposal problem) following grinding for the more-valuable oil-component (and its attendant solvent-extraction). Notice that, irrationally, the oil itself, which is the object of the processing (and main value in the bean), generates less concern than the protein, which is a by-product and only incidentally involved.
Soybean is the best source of complete, balanced amino-acid protein in the plant-world. By far. Animal-nutrition science tells us that soy is not desirable as a staple food-base; you should not try to ‘live on it’, alone. Like other beans, there is a limit to how much of it a critter is going to be interested in eating. But well within the optimum range, soy is a dramatic protein-supplement, within a primarily plant-based (and thus, protein-challenged) diet. Soy grows readily in the home garden. So there is real value, at the personal level, in understanding the taboo.
The demonization of soybean is seen in the 1973 dystopian science-fiction movie, Soylent Green, which was based on a book written in 1966. The bean itself was essential innocent in the story … the soybean-lentil food-product (Soylent) was secretly fortified (by the evil government) with ground-up human bodies, and it was this source of added-supplement that consumers supposed found irresistibly, insanely delicious. Indeed, any added animal-fat & protein supplementation of a purely plant-based feed-ration will improve its palatability (and nutritional value) … both for livestock and for humans too.
Soy contains a substance known to chemists as an isoflavone, which bear a degree of chemical resemblance to the hormone estrogen. That isoflavones ever produce any estrogen-effect in animals lacks good or credible scientific support (and it would big-time ‘Big Pharma’ valuable & exploitable, if it did). Nonetheless, we now have the synonym term Phytoestrogen, specially emphasizing a ‘useful implication’ that these substances have hormone-activity. (Thus supposedly, eg, forcing female children into early puberty, and promoting undesirable changes in both younger & older males.)
More-generally, in-general, humans & other animals cannot readily obtain homone-activity by eating a hormone, because hormones are proteins, and as such they are simply digested along with any other protein that is ingested. All that one gets from eating hormone-molecules, is the generic amino acids. Animals – and humans – do not directly utilize proteins that are in their diet, but instead must break them down into amino acids, absorb those, and then build new proteins internally, from the amino acids. Still, the movement to identify isoflavones as dangerous (and their presence in food products as unhealthful at best, and nefarious or diabolical at worst) appears to be experiencing positive growth.
Cooking coagulates proteins (and makes them more-digestible). Proteins that have been denatured in this way or in other ways, no longer have the properties that they possessed in the active, unmodified form. Hormone-molecules that have been coagulated or otherwise denatured, no longer have any potential to play a hormone-role. They’re cooked.
Premarine, or PREMARINE, is the usual pharmaceutical supply of estrogen for humans. The word Premarine derives from the source, which is Pregnant Mare Urine. The context & conditions under which the raw material is obtained is distinctly unattractive at best, and by some standards, more or less ethically objectionable. If we could get a useable estrogen-supplement starting-base from soybeans or other plants, it would be a good thing, and a whole lot less hassle & expense than getting it from horse-pee. Hmm?
Oil is extracted from ground soybeans, using the hydrocarbon solvent hexane, which is a main component of the hydrocarbon-mixture known as gasoline. Hexane was chosen for this process, in part because it is easy to remove, after it has served its role as a solvent in the recovery of the soybean oil. Standards and testing for removal of the hexane are high. Hexane, along with other hydrocarbons, is found in many natural foods, such as citrus and other fruits, filbert nuts, various mushrooms, etc. Solvent-abuse (huffing gasoline) delivers very large doses, yet acute toxicity of hexane is not easily identified. Long-term solvent huffing & sniffing results in damage to the patient, but it is not clear what the role of hexane is here, if any.
Solvent-extraction is very widespread & fundmental technology, throughout the food industry, using hexane either alone or more commonly in conjunction with other solvents. The whole, unprocessed bean has not been subjected to any solvent process, and is completely free of any associated concerns.