Concerns Regarding Soybeans

Date: 10/14/98

updated 9-12-00

History of Soybeans Soybeans come to us from the Orient. During the Chou Dynasty (1134-246 BC) the soybean was designated one of the five sacred grains, along with barley, wheat,  millet and rice. However, the pictograph for the soybean, which dates from earlier times, indicates that it was not first used as a food; for whereas the pictographs for the other four grains show the seed and stem structure of the plant, the pictograph for the soybean emphasizes the root structure. Agricultural literature of the period speaks frequently of the soybean and its use in crop rotation.

Apparently the soy plant was initially used as a method of fixing nitrogen. The soybean did not serve as a food until the discovery of fermentation techniques, sometime during the Chou Dynasty.

Thus the first soy foods were fermented products like tempeh, natto, miso and shogu (soy or tamari sauce).

At a later date, possibly in the 2nd century B.C., Chinese scientists discovered that a puree of cooked soybeans could be precipitated with calcium sulfate or magnesium sulfate (plaster of Paris or Epsom salts) to make a smooth pale curd -tofu or bean curd. The use of fermented and precipitated soy products soon spread to other parts of the Orient, notably Japan and Indonesia. Although the highly flavored fermented products have elicited greater interest among scientists and epicures, it is the bland precipitated products that are most frequently used, accounting for approximately 90% of the processed soybeans consumed in Asia today. The increased reliance on bean curd as a source of protein, which occurred between 700 A. D. and the present time, has not necessarily been a beneficial change for the populations of the Orient and Southeast Asia.

Fit for Human Consumption? The Chinese, did not eat the soybean as they did other pulses (legumes) such as the lentil, because the soybean contains large quantities of a number of harmful a substances. First among them are potent enzyme inhibitors which block the action of trypsin and other enzymes needed for protein digestion.

These"antinutrients" are not completely deactivated during ordinary cooking and can produce serious gastric distress, reduced protein digestion and chronic deficiencies in amino acid uptake.

In test animals, diets high in trypsin inhibitors cause enlargement and pathological conditions of the pancreas, including cancer. The soybean also contains hemagglutinin, a clot promoting substance that causes red blood cells to clump together. Trypsin inhibitors and hemagglutinin have been rightly labeled growth depressant substances.

Fortunately they are deactivated during the process of fermentation. However, in precipitated products, enzyme inhibitors concentrate in the soaking liquid rather than in the curd. Thus in tofu and bean curd, these enzyme inhibitors are reduced in quantity, but not completely eliminated.

Soybeans are also high in phytic acid or phytates. This is an organic acid, present in the bran or hulls of all seeds, which blocks the uptake of essential minerals-calcium, magnesium, iron and especially zinc-in the intestinal tract.

Although not a household word, phytates have been extensively studied. Scientists are in general agreement that grain and legume based diets high in phytates contribute to widespread mineral deficiencies in third world countries.

Analysis shows that calcium, magnesium, iron and zinc are present in the plant foods eaten in these areas, but the high phytate content of soy and rice based diets prevents their absorption. The soybean has a higher phytate content than any other grain or legume that has been studied. Furthermore, it seems to be highly resistant to many phytate reducing techniques such as long, slow cooking. Only a long period of fermentation will significantly reduce the phytate content of soybeans. Thus fermented products such as tempeh and miso provide nourishment that is easily assimilated, but the nutritional value of tofu and bean curd, both high in phytates, is questionable.

When precipitated soy products are consumed with meat, the mineral blocking effects of the phytates are reduced. The Japanese traditionally eat tofu as part of a mineral-rich fish broth. 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. Zinc is called the intelligence mineral because it is needed for optimal development and functioning of the brain and nervous system. It plays a role in protein synthesis and collagen formation, it Is involved in thc blood sugar control mechanism and thus protects against diabetes; it is needed for a healthy reproductive system.

Zinc is a key component in numerous vital enzymes and plays a role in the immune system. Phytates found in soy products interfere with zinc absorption more completely than with other minerals. Literature extolling soy products tends to minimize the role of zinc in human physiology, and to gloss over the deleterious effect of diets high in phytic acid.

Milk drinking is given as the reason second generation Japanese in America grow taller than their native ancestors. Some investigators postulate that the reduced phytate content of the American diet-whatever maybe its other deficiencies-is the true explanation, pointing out that Asian and Oriental children who do not get enough meat and fish products to counteract the effects of a high phytate diet, frequently suffer rickets, stunting and other growth problems.

Marketing the Soybean The truth is, however, that most Americans are unlikely to adopt traditional soy products as their principle food. Tofu, bean curd and tempeh have disagreeable texture and are too bland for the Western palate; pungent and tasty miso and natto lose out in taste; only soy sauce enjoys widespread popularity as a condiment. The soy industry has therefore looked for other ways to market the superabundance of soybeans now grown in the United States.

Large scale cultivation of the soybean in the United States began only after the Second World War, and quickly rose to 140 billion pounds per year. Most of the crop is made into animal feed, soy oil for hydrogenated fats margarine and shortening. During the past 20 years, the industry has concentrated on finding markets for the byproducts of soy oil manufacture, including soy "lecithin", made from the oil sludge, and soy protein products, made from defatted soy flakes, a challenge that has involved overcoming consumer resistance to soy products, generally considered tasteless "poverty foods.

The quickest way to gain product acceptability in the less affluent society," said a soy industry spokesman, " ... is to have the product consumed on its own merit in a more affluent society." Hence the proliferation of soy products resembling traditional American foods-soy milk for cows milk, soy baby formula, soy yogurt, soy ice cream, soy cheese, soy flour for baking and textured soy protein as meat substitutes, usually promoted as high protein, low-fat, no cholesterol "health foods" to the upscale consumer increasingly concerned about his health. The growth of vegetarianism among the more affluent classes has greatly accelerated the acceptability and use of these artificial products. Unfortunately they pose numerous dangers.

Processing Denatures and Dangers Remain The production of soy milk is relatively simple. In order to remove as much of the trypsin inhibitor content as possible, the beans are first soaked in an alkaline solution. The pureed solution is then heated to about 115 degrees Centigrade in a pressure cooker. This method destroys most (but not all) of the anti-nutrients but has the unhappy side effect of so denaturing the proteins that they become very difficult to digest and much reduced in effectiveness. The phytate content remains in soy milk to block the uptake of essential minerals. In addition, the alkaline soaking solution produces a carcinogen, lysinealine, and reduces the cystine content, which is already low in the soybean. Lacking cystine, the entire protein complex of the soybean becomes useless unless the diet is fortified with cystine-rich meat, eggs, or dairy products.

Most soy products that imitate traditional American food items, including baby formulas and some brands of soy milk, are made with soy protein isolate, that is the soy protein isolated from the carbohydrate and fatty acid components that naturally occur in the bean. Soy beans are first ground and subjected to high-temperature and solvent extraction processes to remove the oils. The resultant defatted meal is then mixed with an alkaline solution and sugars in a separation process to remove fiber. Then it is precipitated and separated using an acid wash. Finally the resultant curds are neutralized in an alkaline solution and spray dried at high temperatures to produce high protein powder.

This is a highly refined product in which both vitamin and protein quality are compromised-but some trypsin inhibitors remain, even after such extreme refining. Trypsin inhibitor content of soy protein isolate can vary as much as 5-fold. In rats, even low level trypsin inhibitor soy protein isolate feeding results in reduced weight gain compared to controls. Soy product producers are not required to state trypsin inhibitor content on labels, nor even to meet minimum standards, and the public, trained to avoid dietary cholesterol, a substance vital for normal growth and metabolism, has never heard of the potent anti-nutrients found in cholesterol-free soy products.

Soy Formula Is Not the Answer Soy protein isolate is the main ingredient of soy-based infant formulas. Along with trypsin inhibitors, these formulas have a high phytate content. Use of soy formula has caused zinc deficiency in infants. Aluminum content of soy formula is 10 times greater than milk based formula, and 100 times greater than unprocessed milk. Aluminum has a toxic effect on the kidneys of infants, and has been implicated as cause in Alzheimer's in adults.

Soy milk formulas are often given to babies with milk allergy; but allergies to soy are almost as common as those to milk. Soy formulas lack cholesterol which is absolutely essential for the development of the brain and nervous system; they also lack lactose and galactose, which play an equally important role in the development of the nervous system. I would strongly discourage the use of soy formulas.

Nitrosamines, which are potent carcinogens, are often found in soy protein foods, and are greatly increased during the high temperature drying process. Not surprisingly, animal feeding studies show a lower weight gain for rats on soy formula than those on whole milk, high-lactose formula; similar results have been observed in children on macrobiotic diets which include the use of soy milk and large amounts of whole grains. Children brought up on high-phytate diets tend to be thin and scrawny.

Fabricated Soy Foods A final indignity to the original soy bean is  high-temperature, high-pressure extrusion processing of soy protein isolate to product textured vegetable protein (TVP). Numerous artificial flavorings, particularly MSG, are added to TVP products to mask their strong "beany" taste, and impart the flavor of meat. Soy protein isolate and textured vegetable protein are used extensively in school lunch programs, commercial baked goods, diet beverages and fast food products. They are heavily promoted in third world countries and form the basis of many food give-away programs. These soy products greatly inhibit zinc and iron absorption; in test animals they cause enlarged organs, particularly the pancreas and thyroid gland, and increased deposition of fatty acids in the liver.

Human feeding tests to determine the cholesterol lowering properties of soy protein isolate have not shown them to be effective. Nevertheless, they are often promoted as having beneficial effects on cholesterol levels. Cancer Preventing or Cancer Causing? The food industry also touts soy products for their cancer preventing properties. Isoflavone aglycones are anticarcinogenic substances found in traditionally fermented soybean products. However, in non-fermented soy products such as tofu and soy milk, these isoflavones are present in an altered form as beta-glycoside conjugates, which have no anti-carcinogenic effect. Some researchers believe the rapid increase in liver and pancreatic cancer in Africa is due to the introduction of soy products there.

The fatty acid profile of the soybean includes large amounts of beneficial omega-3 fatty acids compared to other pulses legumes); but these omega-3 fatty acids are particularly susceptible to rancidity when subjected to high pressures and temperatures. This is exactly what is required to remove oil from the bean, as soybean oil is particularly difficult to extract. hexane or other solvents are always used to extract oil from soybeans, and traces remain in the commercial product.

While fermented soy products contain protein, vitamins, anti-carcinogenic substances and important fatty acids, they can under no circumstances be called nutritionally complete. Like all pulses, the soybean lacks vital sulfur-containing amino acids cystine and methionine. These are usually supplied by rice and other grains in areas where the soybean is traditionally consumed. Soy should never be considered as a substitute for animal products like meat or milk.

Claims that fermented soy products like tempeh can be relied on as a source of vitamin B12, necessary for healthy blood and nervous system, have not been supported by scientific research.,' Finally, soybeans do not supply all-important fat soluble vitamins D and preformed A (retinol) which act as catalysts for the proper absorption and utilization of all minerals and water soluble vitamins in the diet.

These "fat soluble activators" are found only in certain animal foods such as organ meats, butter, eggs, fish and shellfish. Carotenes from plant foods and exposure to sunlight are not sufficient to supply the body's requirements for vitamins A and D. Soy products often replace animal products in third world countries where intake of B12 and fat soluble A and D are already low. Soy products actually increase requirements for vitamins B12 and D.

Are soy products easy to digest, as claimed? Fermented soy products probably are; but unfermented products with their cargo of phytates, enzyme inhibitors, rancid fatty acids and altered proteins most certainly are not. Pet food manufacturers promote soy free dog and cat food as "highly digestible"

Only Fermented Soy Products Are Safe To summarize, traditional fermented soy products such as miso, natto and tempeh, which are usually made with organically grown soybeans, have a long history of use that is generally beneficial when combined with other elements of the Oriental diet including rice, sea foods, fish broth, organ meats and fermented vegetables. The value of precipitated soybean products is problematical, especially when they form the major source of protein in the diet. Modern soy products including soy milks and artificial meat and dairy products made from soy protein isolate and textured vegetable protein are new to the diet and pose a number of serious problems.

The above information was abstracted from an article written by Sally Fallon and Mary Enig, Ph.D. (an international expert renown in the field of lipid chemistry) for Health Freedom News in September of 1995.

Protein Needs for Blood Type A People Blood type A people should be nearly vegetarians. The above information should make it clear that you should avoid most soy products unless they are fermented (tempeh and miso). You should not have soy protein or tofu. To obtain optimal protein though you will need to eat about a dozen organic eggs per week, unless you are allergic to them. Try not to eat them on consecutive days. You should also soak your seeds  and nuts overnight to deactivate the ezymye inhibitors and phytates.

Generally you will need around one cup of each for a protein at a meal. Spirulina is a type of blue-green algae that is nearly two-thirds protein. It also has large amounts of chlorophyll and is very valuable to help detoxify the body. You will need about twenty to thirty tables though to use that as a protein replacement for a meal. I strongly recommend this for at least 4-6 times per week for anyone who is sick

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Copyright © 1998 Optimal Wellness Center

Last modified: April 21, 1998


Sep 12, 2000

About the Brain > Diet and Nutrition

The Trouble With Tofu: Soy and the Brain

John D. MacArthur

"Tofu Shrinks Brain!" Not a science fiction scenario, this sobering soybean revelation is for real. But how did the "poster bean" of the '90s go wrong? Apparently, in many ways — none of which bode well for 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]

"The test results were about equivalent to what they would have been if they were five years older," said lead researcher Dr. Lon R. White from the Hawaii Center for Health Research. For the guys who ate no tofu, however, they tested as though they were five years younger.

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."

Phytoestrogens — Soy Self Defense

Tofu and other soybean foods contain isoflavones, three-ringed molecules bearing a structural resemblance to mammalian steroidal hormones. White and his fellow researchers speculate that soy's estrogen-like compounds (phytoestrogens) might compete with the body's natural estrogens for estrogen receptors in brain cells.

Plants have evolved many different strategies to protect themselves from predators. Some have thorns or spines, while others smell bad, taste bad, or poison animals that eat them. Some plants took a different route, using birth control as a way to counter the critters who were wont to munch.

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.

Toxicologists Concerned About Soy's Health Risks

The soy industry says that White's study only shows an association between tofu consumption and brain aging, but does not prove cause and effect. On the other hand, soy experts at the National Center for Toxicological Research, Daniel Sheehan, Ph.D., and Daniel Doerge, Ph.D., consider this tofu study very important. "It is one of the more robust, well-designed prospective epidemiological studies generally available. . . We rarely have such power in human studies, as well as a potential mechanism."

In a 1999 letter to the FDA (and on the ABC News program 20/20), the two toxicologists expressed their opposition to the agency's health claims for soy, saying the Honolulu study "provides evidence that soy (tofu) phytoestrogens cause vascular dementia. Given that estrogens are important for maintenance of brain function in women; that the male brain contains aromatase, the enzyme that converts testosterone to estradiol; and that isoflavones inhibit this enzymatic activity, there is a mechanistic basis for the human findings." [3]

Although estrogen's role in the central nervous system is not well understood, White notes that "a growing body of information suggests that estrogens may be needed for optimal repair and replacement of neural structures eroded with aging."

One link to the puzzle may involve calcium-binding proteins, which are associated with protection against neurodegenerative diseases. In recent animal studies at Brigham Young University's Neuroscience Center, researchers found that consumption of phytoestrogens via a soy diet for a relatively short interval can significantly elevate phytoestrogens levels in the brain and decrease brain calcium-binding proteins. [4]

Concerns About Giving Soy to Infants

The most serious problem with soy may be its use in infant formulas. "The amount of phytoestrogens that are in a day's worth of soy infant formula equals 5 birth control pills," says Mary G. Enig, Ph.D., president of the Maryland Nutritionists Association. She and other nutrition experts believe that infant exposure to high amounts of phytoestrogens is associated with early puberty in girls and retarded physical maturation in boys. [5]

A study reported in the British medical journal Lancet found that the "daily exposure of infants to isoflavones in soy infant-formulas is 6-11 fold higher on a bodyweight basis than the dose that has hormonal effects in adults consuming soy foods." (A dose, equivalent to two glasses of soy milk per day, that was enough to change menstrual patterns in women. [6]) In the blood of infants tested, concentrations of isoflavones were 13000-22000 times higher than natural estrogen concentrations in early life. [7]

Soy Interferes with Enzymes

While soybeans are relatively high in protein compared to other legumes, Enig says they are a poor source of protein because other proteins found in soybeans act as potent enzyme inhibitors. These "anti-nutrients" block the action of trypsin and other enzymes needed for protein digestion. Trypsin inhibitors are large, tightly folded proteins that are not completely deactivated during ordinary cooking and can reduce protein digestion. Therefore, soy consumption may lead to chronic deficiencies in amino acid uptake. [8]

Soy's ability to interfere with enzymes and amino acids may have direct consequence for the brain. As White and his colleagues suggest, "isoflavones in tofu and other soyfoods might exert their influence through interference with tyrosine kinase-dependent mechanisms required for optimal hippocampal function, structure and plasticity." [2]

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. [9]

Tyrosine, Dopamine, and Parkinson's Disease

The brain uses the amino acids tyrosine or phenylalanine to synthesize the key neurotransmitters dopamine and norepinephrine, brain chemicals that promote alertness and activity. Dopamine is crucial to fine muscle coordination. People whose hands tremble from Parkinson's disease have a diminished ability to synthesize dopamine. An increased incidence of depression and other mood disorders are associated with low levels of dopamine and norepinephrine. Also, the current scientific consensus on attention-deficit disorder points to a dopamine imbalance.

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." [10]

Researchers at Sweden's Karolinska Institute at the National Institutes of Health and are finding a connection between tyrosine hydroxylase activity, thyroid hormone receptors, and depleted dopamine levels in the brain — particularly in the substantia nigra, a region associated with the movement difficulties characteristic of Parkinson's disease. [11-13]

Soy Affects the Brain via the Thyroid Gland

Tyrosine is crucial to the brain in another way. It's needed for the body to make active thyroid hormones, which are a major physiological regulator of mammalian brain development. By affecting the rate of cell differentiation and gene expression, thyroid hormones regulate the growth and migration of neurons, including synaptic development and myelin formation in specific brain regions. Low blood levels of tyrosine are associated with an underactive thyroid gland.

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. [14] 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." [15]

Japanese researchers studied effects on the thyroid from soybeans administered to healthy subjects. They reported that consumption of as little as 30 grams (two tablespoons) of soybeans per day for only one month resulted in a significant increase in thyroid stimulating hormone (TSH), which is produced by the brain's pituitary gland when thyroid hormones are too low. Their findings suggested that "excessive soybean ingestion for a certain duration might suppress thyroid function and cause goiters in healthy people, especially elderly subjects." [16]

Thyroid Hormones and Fetal Brain Development

Thyroid alterations are among the most frequently encountered autoimmune conditions in children. Researchers at Cornell University Medical College showed that the "frequency of feedings with soy-based milk formulas in early life was significantly higher in children with autoimmune thyroid disease." [17] In a previous study, they found that twice as many diabetic children had received soy formula in infancy as compared to non-diabetic children. [18]

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." [19]

Thyroid hormones exert their influence during discrete windows of time. Inappropriate hormone levels can have a devastating effect on the developing human brain, especially during the first 12 weeks of pregnancy when the fetus depends on the mother's thyroid hormones for brain development. After that, both maternal and fetal thyroid hormone levels affect the central nervous system.

A 1999 study published in the New England Journal of Medicine showed that pregnant women with underactive thyroids were four times more likely to have children with low IQs if the disorder is left untreated. The study found that 19% of the children born to mothers with thyroid deficiency had IQ scores of 85 or lower, compared with only 5% of those born to mothers without such problems. [20]

Thyroid, Brain, and Environmental Toxins

Children exposed prenatally and during infancy to common environmental toxins like dioxin and polychlorinated biphenyls (PCBs) can suffer behavioral, learning, and memory problems because these chemicals may be disrupting the normal action of thyroid hormone. [21]

Soybeans grown in the United States contain residues of the pesticide dieldrin, an organochlorine similar to DDT. Although both chemicals were banned in the 1970s, dieldrin still persists in soils and is absorbed through the roots. Today it is the most toxic residue found on domestic soybeans. [22] In Silent Spring, Rachel Carson warned that dieldrin is nearly 50 times as poisonous as DDT. In addition to disrupting hormones, it can have long delayed neurological effects, ranging from loss of memory to mania. [23]

Combinations of insecticides, weed killers, and artificial fertilizers — even at low levels — have measurable detrimental effects on thyroid and other hormones as well as on the brain. [24] EPA scientists now want to upgrade the commonly used herbicide, atrazine, to a "likely carcinogen." In animal tests, atrazine attaches to sites on the hypothalamus, a crucial brain region involved with regulating levels of stress and sex hormones. [25]

Individuals newly diagnosed with Parkinson's disease were more than twice as likely to have been exposed to insecticides in their home, compared to those without the disease. [26]

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]

In May 2000, Boston Physicians for Social Responsibility released their report, "The Toxic Threats to Child Development." In the section on neurotoxins, they concluded: "Studies in animals and human populations suggest that fluoride exposure, at levels that are experienced by a significant proportion of the population whose drinking water is fluoridated, may have adverse impacts on the developing brain." [31]

Iodine vs. Fluorine

The thyroid gland uses tyrosine and the natural element iodine to make thyroxine (T4), a thyroid hormone containing four iodine atoms. The other, much more biologically active thyroid hormone is tri-iodothyronine (T3), which has three iodine atoms. Lack of dietary iodine has long been identified as the problem in diminished thyroid hormone synthesis.

According to the International Council for the Control of Iodine Deficiency Disorders: "Iodine deficiency has been called the world's major cause of preventable mental retardation. Its severity can vary from mild intellectual blunting to frank cretinism, a condition that includes gross mental retardation, deaf mutism, short stature, and various other defects. . . The damage to the developing brain results in individuals poorly equipped to fight disease, learn, work effectively, or reproduce satisfactorily."

This crucial role of iodine is another reason why the thyroid gland is especially vulnerable today. Canadian researcher Andreas Schuld has documented more than 100 studies during the last 70 years that demonstrate adverse effects of fluoride on the thyroid gland. [32] Schuld says, "Fluorine, being the strongest in the group of halogens, will seriously interfere with iodine and iodine synthesis, forcing more urinary elimination of ingested iodine as fluoride ingestion or absorption increases."

Fluorides were actually used in the past, specifically to reduce thyroid function. In the 1930s through to the 1960s fluorides at 0.9mg to 4.5mg/day were given as effective anti-thyroid medication to hyperthyroid patients." [33] Russian researchers in the 1980s concluded that prolonged consumption of drinking water with a raised fluorine content was a risk factor of more rapid development of thyroid pathology. [34]

A major source of fluoride exposure in the United States is fluoridated drinking water — including foods and drinks manufactured and processed with this treated water. (Only about 5% of the world's population is fluoridated, and more than half live in North America. 99% of western continental Europe has rejected, banned, or stopped the addition of fluoride compounds to their drinking water. [35]) Also, approximately 45 million pounds of hydrogen fluoride are released from U.S. coal-fired plants every year into the environment.

Soy Phytates Inhibit Zinc Absorption

Another way that soybeans may affect brain function is because of their phytic acid content. Phytic acid is an organic acid present in the outer portion of all seeds. Also known as phytates, they block the uptake of essential minerals in the intestinal tract: calcium, magnesium, iron, and especially zinc. According to research cited by the Weston A. Price Foundation, soybeans have very high levels of a form of phytic acid that is particularly difficult to neutralize — and which interferes with zinc absorption more completely than with other minerals.

The soy industry acknowledges the problem, noting that "one-half cup of cooked soybeans contains one mg of zinc. However, zinc is poorly absorbed from soyfoods." As for iron, "both phytate and soy protein reduce iron absorption so that the iron in soyfoods is generally poorly absorbed." [36]

Nutritionist Sally Fallon, author of Nourishing Traditions: The Cookbook that Challenges Politically Correct Nutrition and the Diet Dictocrats, says that as early as 1967, researchers testing soy formula found that it caused negative zinc balance in every infant to whom it was given. Even when the diets were additionally supplemented with zinc, there was a strong correlation between phytate content in formula and poor growth. She warns that "a reduced rate of growth is especially serious in the infant as it causes a delay in the accumulation of lipids in the myelin, and hence jeopardizes the development of the brain and nervous system."

Zinc and the Brain

Relatively high levels of zinc are found in the brain, especially the hippocampus. Zinc plays an important role in the transmission of the nerve impulse between brain cells. Deficiency of zinc during pregnancy and lactation has been shown to be related to many congenital abnormalities of the nervous system in offspring. In children, "insufficient levels of zinc have been associated with lowered learning ability, apathy, lethargy, and mental retardation." [37]

The USDA references a study of 372 Chinese school children with very low levels of zinc in their bodies. The children who received zinc supplements had the most improved performance — especially in perception, memory, reasoning, and psychomotor skills such as eye-hand coordination. Three earlier studies with adults also showed that changes in zinc intake affected cognitive function. [38]

New research has identified a specific contingent of neurons, called "zinc-containing" neurons, which are found almost exclusively in the forebrain, where in mammals they have evolved into a "complex and elaborate associational network that interconnects most of the cerebral cortices and limbic structures." This suggests the importance of zinc in the normal and pathological processes of the cerebral cortex. [39] Furthermore, age-related tissue zinc deficiency may contribute to brain cell death in Alzheimer's dementia. [40]

Safe Soy

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.


Links to Further Information

Soy Online Service

Weston A. Price Foundation


1. White LR, Petrovich H, Ross GW, Masaki KH, Association of mid-life consumption of tofu with late life cognitive impairment and dementia: the Honolulu-Asia Aging Study. Fifth International Conference on Alzheimer's Disease, #487, 27 July 1996, Osaka, Japan.

2. White LR, Petrovitch H, Ross GW, Masaki KH, Hardman J, Nelson J, Davis D, Markesbery W, Brain aging and midlife tofu consumption. J Am Coll Nutr 2000 Apr;19(2):242-55.

3. Doerge and Sheehan, Letter to the FDA, Feb 18, 1999.

4. Lephart ED, Thompson JM, Setchell KD, Adlercreutz H, Weber KS, Phytoestrogens decrease brain calcium-binding proteins... Brain Res 2000 Mar 17;859(1):123-31.

5. Soy Infant Formula Could Be Harmful to Infants: Groups Want it Pulled. Nutrition Week, Dec 10, 1999;29(46):1-2.

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7. Setchell KD, Zimmer-Nechemias L, Cai J, Heubi JE, Exposure of infants to phyto-oestrogens from soy-based infant formula. Lancet 1997 Jul 5;350(9070):23-27.

8. Enig MG, Fallon SA, Tragedy and Hype, The Third International Soy Symposium. Nexus Magazine Vol 7, No 3, April-May 2000.

9. O'Dell TJ, Kandel ER, Grant SG, Long-term potentiation in the hippocampus is blocked by tyrosine kinase inhibitors. Nature 1991 Oct 10 353:6344 558-60.

10. Bell JM, Whitmore WL, Cowdery T, Slotkin TA, Perinatal dietary supplementation with a soy lecithin preparation: effects on development of central catecholaminergic neurotransmitter systems. Brain Res Bull 1986 Aug;17(2):189-95.

11. Zetterstrom RH, Williams R, Perlmann T, Olson L, Cellular expression of the immediate early transcription factors Nurr1 and NGFI-B suggests a gene regulatory role in several brain regions including the nigrostriatal dopamine system. Brain Res Mol Brain Res 1996 Sep 5;41(1-2):111-20.

12. Castillo SO, Baffi JS, Palkovits M, Goldstein DS, Kopin IJ, Witta J, Magnuson MA, Nikodem VM, Dopamine biosynthesis is selectively abolished in substantia nigra... Mol Cell Neurosci 1998 May;11(1-2):36-46.

13. Baffi JS, Palkovits M, Castillo SO, Mezey E, Nikodem VM, Differential expression of tyrosine hydroxylase in catecholaminergic neurons of neonatal wild-type and Nurr1-deficient mice. Neuroscience 1999;93(2):631-42.

14. Shepard TH, Soybean goiter. New Eng J Med 1960;262:1099-1103.

15. Divi RL, Chang HC, Doerge DR, Anti-thyroid isoflavones from soybean: isolation, characterization, and mechanisms of action.Biochem Pharmacol 1997 Nov 15;54(10):1087-96.

16. Ishizuki Y, Hirooka Y, Murata Y, Togashi K,The effects on the thyroid gland of soybeans administered experimentally in healthy subjects. Nippon Naibunpi Gakkai Zasshi 1991 May 20;67(5):622-29.

17. Fort P, Moses N, Fasano M, Goldberg T, Lifshitz F, Breast and soy-formula feedings in early infancy and the prevalence of autoimmune thyroid disease in children. J Am Coll Nutr 1990 Apr;9(2):164-67.

18. Fort P, Lanes R, Dahlem S, Recker B, Weyman-Daum M, Pugliese M, Lifshitz FJ, Breast feeding and insulin-dependent diabetes mellitus in children. Am Coll Nutr 1986;5(5):439-41.

19. Regulatory Guidance in Other Countries: New Zealand Ministry of Health Position Statement on Soy Formulas (Adobe Acrobat file).

20. Haddow JE, Palomaki GE, Allan WC, Williams JR, Knight GJ, Gagnon J, O'Heir CE, Mitchell ML, Hermos RJ, Waisbren SE, Faix JD, Klein RZ, Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. N Engl J Med 1999 Aug 19;341(8):549-55.

21. Hauser P, McMillin JM, Bhatara VS, Resistance to thyroid hormone: implications for neurodevelopmental research on the effects of thyroid hormone disruptors. Toxicol Ind Health 1998 Jan-Apr;14(1-2):85-101.

22. Groth E, Benbrook CM, Lutz K, Update: pesticides in children's foods, an analysis of 1998 USDA PDP data on pesticide residues, Consumers Union of U.S., Inc., May, 2000 (Adobe Acrobat file).

23. Hayes WJ, The toxicity of dieldrin to man. Bull World Health Organ 1959;20:891-92.

24. Porter WP, Jaeger JW, Carlson IH, Endocrine, immune and behavioral effects of aldicarb (carbamate), atrazine (triazine) and nitrate (fertilizer) mixtures at groundwater concentrations. Toxicol Ind Health 1999 Jan-Mar;15(1-2):133-50.

25. Watson, Traci, Common herbicide likely causes cancer. USA Today, June 29, 2000.

26. Nelson L, American Academy of Neurology's 52nd annual meeting in San Diego, CA, April 29-May 6, 2000.

27. McGraw M, Bishop N, Jameson R, Robinson MJ, O'Hara M, Hewitt CD, Day JP, Aluminium content of milk formulae and intravenous fluids used in infants. Lancet 1986 Jan 18;1(8473):157.

28. Dabeka RW, McKenzie AD, Lead, cadmium, and fluoride levels in market milk and infant formulas in Canada. J Assoc Off Anal Chem 1987;70(4):754-57.

29. Silva M, Reynolds EC, Fluoride content of infant formulae in Australia. Aust Dent J 1996 Feb;41(1):37-42.

30. Pendrys DG, Katz RV, Morse DE, Risk factors for enamel fluorosis in a fluoridated population. Am J Epidemiol 1994 Sep 1;140(5):461-71.

31. Schettler T, Stein J, Reich F, Valenti M, In Harm's Way: Toxic Threats to Child Development. Greater Boston Physicians for Social Responsibility, May 2000.

32. Studies Dealing with Fluoride and the Thyroid Gland. See also: Fluoride Controversy in Townsend Letter for Doctors and Patients.

33. Galetti PM, Joyet, G, Effect of fluorine on thyroidal iodine metabolism in hyperthyroidism. J Clin Endocrinol 1958;18:1102-10.

34. Bachinskii PP, Gutsalenko OA, Naryzhniuk ND, Sidora VD, Shliakhta AI, Action of the body fluorine of healthy persons and thyroidopathy patients on the function of hypophyseal-thyroid the system. Probl Endokrinol (Mosk) 1985 Nov-Dec;31(6):25-29.

35. Fluoridation Status of Some Countries, Fluoride: Protected Pollutant or Panacea?

36. Soy Nutritive Content, United Soybean Board.

37. Pfeiffer CC, Braverman ER, Zinc, the brain and behavior. Biol Psychiatry 1982 Apr;17(4):513-32.

38. U.S. Department of Agriculture, Agricultural Research Service, Food & Nutrition Research Briefs, July 1997.

39. Frederickson CJ, Suh SW, Silva D, Frederickson CJ, Thompson RB, Importance of zinc in the central nervous system: the zinc-containing neuron. J Nutr 2000 May;130(5S Suppl):1471S-83S.

40. Ho LH, Ratnaike RN, Zalewski PD, Involvement of intracellular labile zinc in suppression of DEVD-caspase activity in human neuroblastoma cells. Biochem Biophys Res Commun 2000 Feb 5;268(1):148-54.

For an index of John D. MacArthur's other reports in, please click here.

This information is not intended to be a substitute for professional medical advice. You should not use this information to diagnose or treat a health problem or disease without consulting with a qualified health care provider. Please consult your health care provider with any questions or concerns you may have regarding your condition.


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