Some say its health food and should be consumed regularly, even supplemented, others say its dangerous - hide the children, lock the doors and protect yourself from the soy!!!!
Lets look at the recent literature about soy. Soy contains phyto-estrogens, which are the plants hormones that are molecularly very similar to human hormones. They can bind weakly to estrogen receptors in the body. For people with estrogen-sensitive tumors (e.g. some breast cancers of prostate cancer) its not such a good idea to have these receptor sites over-stimulated.
Menopausal women who have ovaries, which no longer produce the estrogen they once did, may benefit from this hormonal boost.
It's all a matter of moderation and suitability. Excess intake of soy can have adverse hormonal effects involving the reproductive organs and the thyroid. Soy decreases testosterone so men may experience low libido and decreased sperm count. Women may experience an array of symptoms since the thyroid gland will also be affected. When there is too much soy in the system, a woman may complain of fatigue, low libido, heavy menstrual flow, cramping, infertility, depression, hair loss, dry skin and weight gain. It is the genistein that has been blamed for the "irreversible damage" to the enzyme that synthesizes thyroid hormone.
The processing of soy also makes it a less than desirable food item since the process involves chemicals, such as aluminum, high heat and pressure, robbing it of nutrients it may have had. The high temperature denatures the protein so that it is virtually useless as a protein source. Some people even refer to soy as an anti-nutrient since it contains protease inhibitors, phytates, saponins, isoflavones which interfere with nutrient digestion, mineral absorption, and the immune system.
Phytic acid, from the hull, is the part that blocks mineral absorption especially calcium, magnesium, copper, iron and zinc. Unfortunately, cooking soy does not deactivate the phytates like it does for other foods that are high in phytic acid. Other vitamins actually increase their requirements when soy is consumed, such as Vitamins E, K, D and B12.
Trypsin is an enzyme that is responsible for the breakdown of proteins and this action is blocked by soy. When proteins are not completely broken down they tend to putrefy in the gut leading to a host of GI symptoms. Research has also shown that when trypsin is continuously inhibited that the pancreas is prone to pathologies, including cancer.
Soy also contains a substance that promotes red blood cells to clot and together with trypsin, this dynamic duo has been shown to inhibit growth. Fermenting soy products inactivates these harmful effects.
It is also important to note that there are many hidden sources of soy including margarine, ice cream, pastas, bread, chips, cereals, canned tuna, fast-food burgers and vegetable oil.
For more information about the deception of the soy industry, read the book, The Whole Soy Story, By Kaayla Daniel. She claims that a safe level of soy is less than 36 g a day, which is similar to what is eaten in Japan, the country with the highest soy consumption. (As a comparison, a cup of tofu weighs 252 g.)
OK, so let's finish with saying something positive about soy. Did you know that soy has the potential to be a plant-based renewable resource that could replace petroleum-based plastics and fuels? Now that's good news for our children!