Why You Should Avoid Soy / The Trouble With Tofu: Soy and the Brain

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Why You Should Avoid Soy / The Trouble With Tofu: Soy and the Brain

The Trouble With Tofu: Soy and the Brain

By 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 , 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,

Sheehan, Ph.D., and 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 G. Enig, Ph.D., president of the land

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,

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 s 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.

For the best organic miso contact:

South River Miso Company

888 Shelburne Falls Road

Comway, MA 01341

413-369-4299

You can also check out their web site:

http://www.southrivermiso.com/

 

Love, Gabby. :0)

http://stemcellforautism.blogspot.com/

 

" I know of nobody who is purely Autistic or purely neurotypical. Even God had

some Autistic moments, which is why the planets all spin. " ~ Jerry Newport