An extensive grasp of informative quotes exposing the many dangers of soy:
The Chinese did not eat unfermented soybeans as they did other legumes such as lentils because the soybean contains large quantities of natural toxins or “antinutrients”. First among them are potent enzyme inhibitors that block the action of trypsin and other enzymes needed for protein digestion.
Blood Clotting Effects
Soybeans also contain haemagglutinin, a clot-promoting substance that causes red blood cells to clump together.
Trypsin inhibitors and haemagglutinin are growth inhibitors. Weanling rats fed soy containing these antinutrients fail to grow normally. Growth-depressant compounds are deactivated during the process of fermentation, so once the Chinese discovered how to ferment the soybean, they began to incorporate soy foods into their diets.
Suppression of Thyroid Function
Soy also contains goitrogens – substances that depress thyroid function.
In 1991, Japanese researchers reported that consumption of as little as 30 grams or two tablespoons of soybeans per day for only one month resulted in a significant increase in thyroid-stimulating hormone.49 Diffuse goiter and hypothyroidism appeared in some of the subjects and many complained of constipation, fatigue and lethargy, even though their intake of iodine was adequate.
Scientists have known for years that isoflavones in soy products can depress thyroid function, causing goiter (enlarged thyroid gland) and autoimmune thyroid disease. In the early 1960s, goiter and hypothyroidism were reported in infants fed soybean diets.  Scientists at the National Center for Toxicological Research showed that the soy isoflavones genistein and daidzein “inhibit thyroid peroxidase-catalyzed reactions essential to thyroid hormone synthesis.” 
Recognizing the risk, Swiss health authorities recommend “very restrictive use” of soy for babies. In England and Australia, public health agencies tell parents to first seek advice from a doctor before giving their infants soy formula. The New Zealand Ministry of Health recommends that “Soy formula should only be used under the direction of a health professional for specific medical indications. . . Clinicians who are treating children with a soy-based infant formula for medical conditions should be aware of the potential interaction between soy infant formula and thyroid function.” 
“There is abundant evidence that some of the isoflavones, including genistein and equal are toxicants… additionally, isoflavones are inhibitors of thyroid peroxidase which makes T3 and T4. Inhibition can be expected to generate thyroid abnormalities including goiter and autoimmune thyroiditis. In fact, infants consuming soy infant formula rich in isoflavones have about a two-fold risk of developing these diseases…While isoflavones may have beneficial effects at some ages or circumstances, this cannot be assumed to be true at all ages. Isoflavones are like other estrogens in that they are two-edged swords, conferring both benefits and risk.
If Asians indeed have lower rates of osteoporosis than Westerners, it is because their diet provides plenty of vitamin D from shrimp, lard and seafood, and plenty of calcium from bone broths. The reason that Westerners have such high rates of osteoporosis is because they have substituted soy oil for butter, which is a traditional source of vitamin D and other fat-soluble activators needed for calcium absorption.
Vegetarians who consume tofu and bean curd as a substitute for meat and dairy products risk severe mineral deficiencies. The results of calcium, magnesium and iron deficiency are well known; those of zinc are less so.
Soybeans are high in phytic acid, present in the bran or hulls of all seeds. It’s a substance that can block the uptake of essential minerals – calcium, magnesium, copper, iron and especially zinc – in the intestinal tract.
Soy Protein Isolate
In feeding experiments, the use of SPI increased requirements for vitamins E, K, D and B12 and created deficiency symptoms of calcium, magnesium, manganese, molybdenum, copper, iron and zinc.26 Phytic acid remaining in these soy products greatly inhibits zinc and iron absorption; test animals fed SPI develop enlarged organs, particularly the pancreas and thyroid gland, and increased deposition of fatty acids in the liver.27
Vitamin D Deficiency
The claim that soy prevents osteoporosis is extraordinary, given that soy foods block calcium and cause vitamin D deficiencies.
Genetically Modified Soy
Additionally 99% a very large percentage of soy is genetically modified and it also has one of the highest percentages contamination by pesticides of any of our foods.
Adding to the natural trouble with soybeans, we are faced with a new Western phenomenon: genetically altered soy. Among other genetically altered, or transgenic foods like corn, apples, tomatoes, squash, strawberries, lettuce, potatoes, wheat and even walnuts (to name just a few), soy is one of the most controversial. MonsantoTM, the multi-million dollar biotechnology leader that brought us rBGH (Bovine Growth Hormone), has been fighting to put genetically altered foods on your table for several years. So far, they are winning. The truth is, unless you’ve been eating ONLY organic foods, it is likely you’ve been tasting Monsanto’s handiwork.
Monsanto has gained millions in profits from sales of its popular herbicide, Roundup?, and in turn has produced several transgenic crops that resist it. Soy is of course among those Roundup-Ready? crops. Being resistant to this powerful herbicide, farmers are able to spray more of it on their crops, resulting in higher levels of toxins in the harvested product. Recent studies have shown that sprayed soybean crops have an elevated estrogen level (much higher than the soybean’s already high levels). As we mentioned earlier, the synergistic effect of these estrogens – especially on children ingesting soy based formula is unknown, but in a recent study reported in Pediatrics raised a few eyebrows. “
Traditionally fermented soy products make a delicious, natural seasoning that may supply important nutritional factors in the Asian diet. But except in times of famine, Asians consume soy products only in small amounts, as condiments, and not as a replacement for animal foods – with one exception. Celibate monks living in monasteries and leading a vegetarian lifestyle find soy foods quite helpful because they dampen libido.
A study of babies born to vegetarian mothers, published in January 2000, indicated just what those changes in baby’s development might be. Mothers who ate a vegetarian diet during pregnancy had a fivefold greater risk of delivering a boy with hypospadias, a birth defect of the penis.70 The authors of the study suggested that the cause was greater exposure to phytoestrogens in soy foods popular with vegetarians.
Hyperplasia and Breast Cancer
Thousands of women are now consuming soy in the belief that it protects them against breast cancer. Yet, in 1996, researchers found that women consuming soy protein isolate had an increased incidence of epithelial hyperplasia, a condition that presages malignancies.45 A year later, dietary genistein was found to stimulate breast cells to enter the cell cycle – a discovery that led the study authors to conclude that women should not consume soy products to prevent breast cancer.46
In part one of this article, we mentioned that assumptions have been made linking soy intake to the low incidence of certain cancers in Asia. “However, an epidemiological study in China has shown that high soy intake is not protective against breast cancer.”1
Birth Control Function
One hundred grams of soy protein – the maximum suggested cholesterol-lowering dose, and the amount recommended by Protein Technologies International – can contain almost 600 mg of isoflavones,52 an amount that is undeniably toxic. In 1992, the Swiss health service estimated that 100 grams of soy protein provided the estrogenic equivalent of the Pill.53
Plants such as soy are making oral contraceptives to defend themselves, says Claude Hughes, Ph.D., a neuroendocrinologist at Cedars-Sinai Medical Center. They evolved compounds that mimic natural estrogen. These phytoestrogens can interfere with the mammalian hormones involved in reproduction and growth — a strategy to reduce the number and size of predators.
Approximately 25 per cent of bottle-fed children in the US receive soy-based formula – a much higher percentage than in other parts of the Western world. Fitzpatrick estimated that an infant exclusively fed soy formula receives the estrogenic equivalent (based on body weight) of at least five birth control pills per day.58 By contrast, almost no phytoestrogens have been detected in dairy-based infant formula or in human milk, even when the mother consumes soy products.
Investigators found that one percent of all girls now show signs of puberty, such as breast development or pubic hair before the age of THREE; by age eight 14.7 percent of Caucasian girls and a whopping 48.3 percent of African-American girls had one or both of these characteristics” states Sally Fallon in the Price-Pottinger article on soy. (For a natural alternative to soy and milk based formula, see Nourishing Traditions, available through PPNF at 619-574-7763).
Interference with the Menstrual Cycle
The core of their concern rests with the chemical make-up of soy: in addition to all the nutrients and protein, exists a natural chemical that mimics estrogen, the female hormone. Some studies in animals show that this chemical can alter sexual development. And in fact, two glasses of soy milk a day, over the course of a month, contains enough of the chemical to change the timing of a woman’s menstrual cycle.
Mental Health Damage
Learning disabilities, especially in male children, have reached epidemic proportions. Soy infant feeding – which began in earnest in the early 1970s – cannot be ignored as a probable cause for these tragic developments.
Damage to the Brain
In a major ongoing study involving 3,734 elderly Japanese-American men, those who ate the most tofu during midlife had up to 2.4 times the risk of later developing Alzheimer’s disease. As part of the three-decade long Honolulu-Asia Aging Study, 27 foods and drinks were correlated with participants’ health. Men who consumed tofu at least twice weekly had more cognitive impairment, compared with those who rarely or never ate the soybean curd. [1,2]
Those participants who consumed tofu in mid-life had lower cognitive function in late life and a greater incidence of Alzheimer’s disease and dementia. “What’s more,” said Dr White, “those who ate a lot of tofu, by the time they were 75 or 80 looked five years older”
What’s more, higher midlife tofu consumption was also associated with low brain weight. Brain atrophy was assessed in 574 men using MRI results and in 290 men using autopsy information. Shrinkage occurs naturally with age, but for the men who had consumed more tofu, White said “their brains seemed to be showing an exaggeration of the usual patterns we see in aging.”
Soy formulas for infants can contain other neurotoxins: aluminum, cadmium, and fluoride. Studies found that aluminum concentrations in soy-based formulas were a 100-fold greater compared to human breast milk, while cadmium content was 8-15 times higher than in milk-based formulas. In an Australian study, the fluoride content of soy-based formulas ranged from 1.08 to 2.86 parts per million. The authors concluded that “prolonged consumption (beyond 12 months of age) of infant formula reconstituted with optimally-fluoridated water could result in excessive amounts of fluoride being ingested.” A study of Connecticut children revealed that mild-to-moderate fluorosis was strongly associated with soy-based infant formula use. [27-30]
Inhibition of Tyrosine Kinase
High amounts of protein tyrosine kinases are found in the hippocampus, a brain region involved with learning and memory. One of soy’s primary isoflavones, genistein, has been shown to inhibit tyrosine kinase in the hippocampus, where it blocked “long-term potentiation,” a mechanism of memory formation. 
Inhibition of Tyrosine Hydroxylase
Soy has been shown to affect tyrosine hydroxylase activity in animals, causing the utilization rate of dopamine to be “profoundly disturbed.” When soy lecithin supplements were given throughout perinatal development, they reduced activity in the cerebral cortex and “altered synaptic characteristics in a manner consistent with disturbances in neural function.” 
To produce soy milk, the beans are first soaked in an alkaline solution, then heated to about 115 degrees C in order to remove as much of the trypsin inhibitors as possible. Fallon says this method destroys most, but not all of the anti-nutrients, however it has the “unhappy side effect of so denaturing the proteins that they become very difficult to digest and much reduced in effectiveness.” Furthermore, phytates remain in soy milk to block the uptake of essential minerals.
Only a long period of fermentation will significantly reduce the phytate content of soybeans, as well as the trypsin inhibitors that interfere with enzymes and amino acids. Therefore, fermented soy products such as tempeh and miso (not tofu) provide nourishment that is easily assimilated.
Safe Soy is No Soy
How Much Soy is Safe? According to the Soy Online Service, for infants, any soy is too much. For adults, just 30 mg of soy isoflavones per day is the amount found to have a perceived negative impact on thyroid function. This amount of soy isoflavones is found in just 5-8 ounces of soy milk, or 1.5 ounces of miso.
- Newest Research On Why You Should Avoid Soy:
- Soy and Brain Damage:
- Soy: Too Good to be True (Part 2 of 2):
- Soy: Miracle or Harmful Part II:
- 2006 Coast to Coast Interview, download here: The Truth About Soy
Top nutritionist Kaayla Daniel, PhD, shared information about soy that the soy industry has tried to suppress.
- Sally Fallon: The Truth About Soy and Why its Toxic – 1/4
- Dr. Kaayla Daniel – The Dangers of a High Soy Diet
- William Campbell Douglass on Soy and Estrogen
- Is soy bad for you?