...The
truth, unfortunately, is far more complex. Soy foods come in a variety
of forms, including many heavily processed modern products. Even good
forms of soy foods must be eaten sparingly-the way they have been eaten
traditionally in Asia. Most important, many respected scientists have
issued warnings stating that the possible benefits of eating soy should
be weighed against the proven risks. Indeed, thousands of studies
link soy to malnutrition, digestive distress, immune-system breakdown,
thyroid dysfunction, cognitive decline, reproductive disorders and
infertility-even cancer and heart disease....
How Much Soy Do Asians Really Eat?
Those who dare to question the benefits of soy tend to receive one stock
answer: Soy foods couldn't possibly have a downside because Asians eat
large quantities of soy every day and consequently remain free of most
western diseases. In fact, the people of China, Japan, and other countries
in Asia eat very little soy. The soy industry's own figures show that
soy consumption in China, Indonesia, Korea, Japan, and Taiwan ranges from
9.3 to 36 grams per day.1 That's grams of soy food, not grams of soy
protein alone. Compare this with a cup of tofu (252 grams) or soy milk
(240 grams).2 Many Americans today think nothing of consuming a cup of
tofu, a couple glasses of soy milk, handfuls of soy nuts, soy "energy
bars," and veggie burgers. Infants on soy formula receive the most of all,
both in quantity and in proportion to body weight.
In short,
there is no historical precedent for eating the large amounts of soy food
now being consumed by infants fed soy formula and vegetarians who favor
soy as their main source of protein, or for the large amounts of soy being
recommended by Dr. Andrew Weil, Dr. Christiane Northrup, and many other
popular health experts. ...
What's more,
the rural poor in China have never seen-let alone feasted on-soy sausages,
chili made with Textured Vegetable Protein (TVP), tofu cheesecake,
packaged soy milk, soy "energy bars," or other newfangled soy products
that have infiltrated the American marketplace. .....
There's
nothing natural about these modern soy protein products. Textured soy
protein, for example, is made by forcing defatted soy flour through a
machine called an extruder under conditions of such extreme heat and
pressure that the very structure of the soy protein is changed. Production
differs little from the extrusion technology used to produce starch-based
packing materials, fiber-based industrial products, and plastic toy parts,
bowls, and plates.16
...The process
of making soy protein isolate (SPI) begins with defatted soybean meal,
which is mixed with a caustic alkaline solution to remove the fiber, then
washed in an acid solution to precipitate out the protein. The protein
curds are then dipped into another alkaline solution and spray-dried at
extremely high temperatures. SPI is then often spun into protein fibers
using technology borrowed from the textile industry. These refining
processes remove "off flavors," "beany" tastes, and some of the worst
flatulence-producing components. They improve digestibility, but vitamin,
mineral, and protein quality are sacrificed, and levels of carcinogens
such as nitrosamines are increased.17-22 SPIs appear in so many
products that consumers would never guess that the Federation of American
Societies for Experimental Biology (FASEB) decreed in 1979 that the only
safe use for SPIs was for sealers for cardboard packages.23...
Antinutrients
and Toxins in Soy
Scientists who have studied the use of soy protein in animal feeds over
the years have discovered a number of components in soy that cause poor
growth, digestive distress, and other health problems.24-27 To
list just a few of these: Protease inhibitors interfere with protein
digestion and have caused malnutrition, poor growth, digestive
distress, and pancreatitis.28 Phytates block mineral absorption,
causing zinc, iron, and calcium deficiencies.29-34 Lectins and
saponins have caused leaky gut and other gastrointestinal and immune
problems.35-36 Oxalates-surprisingly high in soy-may cause problems
for people prone to kidney stones and women suffering from
vulvodynia, a painful condition marked by burning, stinging, and
itching of the external genitalia.37, 38 Finally, oligosaccharides give
soy its notorious reputation as a gas producer. Although these are present
in all beans, soy is such a powerful "musical fruit" that the soy industry
has identified "the flatulence factor" as a major obstacle that
must be overcome for soy to achieve full consumer acceptance.39, 40
Apologists for
soy dismiss such claims, saying that food processing and home cooking
remove most of these antinutrients. In fact, modern processing removes
most of them, but not all. The levels of heat and pressure needed to
remove all protease inhibitors, for example, severely damage soy protein
and make it harder to digest. The trick is to eliminate the most
antinutrients while doing the least damage to the soy protein. Success
varies widely from batch to batch.41-44
For years, the
soy industry tried to improve the quality of animal feeds by finding
better ways to get rid of these undesirable antinutrients. Having failed,
they routinely supplement animal feeds heavily with vitamins, minerals,
and methionine, a sulfur-containing amino acid that is low in soy. Even
so, makers of animal chows are still limited in the amount of soy they
can add without causing growth and fertility problems. Food processors
making soy-protein products for people may or may not add these
supplements. Generally, calcium and vitamin D are added to soy milk so it
can compete with dairy products.
Today, the
soy industry has switched tactics-from trying to remove unwanted
antinutrients to trying to convince people that they are actually a good
thing. Protease inhibitors, saponins, and lectins are being touted as
curers of cancer or lowerers of cholesterol, while phytates are being
recommended for their ability to remove toxic minerals such as cadmium and
excess iron from the body.45-51 Although some of these uses look
promising, it is important to note that researchers are not achieving
these successes using regular soy foods. Most take carefully extracted
components and administer them in carefully measured and monitored
pharmaceutical doses. News headlines to the contrary, there is no reason
to think that just eating a lot of soy foods will do the trick.
Soy Allergens
Soy is one of the top eight allergens that cause immediate
hypersensitivity reactions such as coughing, sneezing, runny nose, hives,
diarrhea, difficulty swallowing, and anaphylactic shock. Delayed allergic
responses are even more common and occur anywhere from several hours to
several days after the food is eaten. These have been linked to sleep
disturbances, bedwetting, sinus and ear infections, crankiness, joint
paint, chronic fatigue, gastrointestinal woes, and other mysterious
symptoms.52, 53
Soy
allergies are on the rise for three reasons: the growing use of soy
infant formula (now 20 to 25 percent of the formula market), the
increase in soy-containing foods in grocery stores, the possibility of
the greater allergenicity of genetically modified soybeans.54
Although severe reactions to soy are rare compared to reactions to
peanuts, tree nuts, fish, and shellfish, soy has been underestimated as a
cause of food anaphylaxis. Recently, after a young girl in Sweden suffered
an asthma attack and died after eating a hamburger that contained only 2.2
percent soy protein, Swedish researchers looked into a possible soybean
connection. They concluded that the soy-in-the-hamburger case was not a
fluke, and that minute amounts of soy "hidden" in regular food had caused
four of the total of five deaths caused by allergic reactions in Sweden
between 1993 and 1996. Of the children who suffered fatal attacks, all had
been able to eat soy without any adverse reactions right up until the
dinner that caused their deaths.55 According to the Swedish Ministry of
Health and Social Affairs, children at highest risk are those who suffer
from peanut allergies and asthma; parents of such children should make
every effort to eliminate all soy from their children's diets.56
Soy and the
Thyroid: A Pain in the Neck
More than 70 years of human, animal, and laboratory studies show that
soybeans put the thyroid at risk. The chief culprits are the plant
hormones in soy known as phytoestrogens or isoflavones.57-59 The United
Kingdom's Committee on Toxicology has identified several populations at
special risk: infants on soy formula, vegans who use soy as their
principal meat and dairy replacements, and men and women who self-medicate
with soy foods and/or isoflavone supplements in an attempt to prevent or
reverse menopausal symptoms, cancer, or heart disease.60
Infants with
congenital hypothyroidism need 18 to 25 percent higher doses of thyroxine
drug than usual if they are bottle-fed with soy formula.61 Likewise,
adults who boost their thyroid with drugs such as Synthroid while also
eating thyroid-inhibiting foods such as soy put extreme stress on their
thyroids. Toxicologist Michael Fitzpatrick, PhD, points out that this is
the way that researchers induce thyroid cancers in laboratory animals.62
Soy and
Reproduction: Breeding Discontent
Scientists have known since the mid-1940s that phytoestrogens can
impair fertility. Fertility problems in cows, sheep, rabbits,
cheetahs, guinea pigs, birds, and mice have all been reported.63, 64
Although scientists discovered only recently that soy lowers testosterone
levels,65 tofu has traditionally been used in Buddhist monasteries to
decrease the libido, and by Japanese women to punish straying husbands.
Humans and animals appear to be the most vulnerable to the effects of soy
estrogens prenatally, during infancy and puberty, during pregnancy and
lactation, and during the hormonal shifts of menopause. Of all these
groups, infants on soy formula are at the highest risk because of their
small size and developmental phase, and because formula is their main
source of nutrient.66, 67
A crucial time
for the programming of the human reproduction system is right after
birth-the very time when bottles of soy formula are given to many
non-breastfed babies. Normally during this period, the body surges with
natural estrogens, testosterones, and other hormones that are meant to
program the baby's reproductive development from infancy through puberty
and into adulthood. For infants on soy formula, this programming may be
interrupted.68-70
Male infants
experience a testosterone surge during the first few months of life and
produce androgens in amounts equal to those of adult men. So much
testosterone at such a tender age is needed to program the body for
puberty, the time when a male's sex organs should develop and he should
begin to express male characteristics such as facial and pubic hair and a
deep voice. If receptor sites intended for the hormone testosterone are
occupied by soy estrogens, however, appropriate development may never take
place.71-74 To date, most of the evidence damning soy formula can be
found only in animal studies, because investigations in which humans' sex
hormone levels are lowered experimentally cannot ethically be done.
However, in the years since soy formula has been in the marketplace,
parents and pediatricians have reported growing numbers of boys whose
physical maturation is either delayed or does not occur at all. Breasts,
underdeveloped gonads, undescended testicles (cryptorchidism), and steroid
insufficiencies are increasingly common. Sperm counts are also
falling.75-79
Soy formula is
bad news for girls as well. Natural estrogen levels approximately double
during the first month of life, then decline and remain at low levels
until puberty. With increased estrogens in the environment in the diet, an
alarming number of girls are entering puberty much earlier than
normal.80-82 One percent of girls now show signs of puberty, such as
breast development or pubic hair, before the age of three. By the age of
eight, 14.7 percent of Caucasian girls and 48.3 percent of African
American girls had one or both of these characteristics.83 The fact that
blacks experience earlier puberties than whites is not a racial difference
but a recent phenomenon.84, 85
Most experts
blame this epidemic of "precocious puberty" on environmental estrogens
from plastics, pesticides, commercial meats, etc., but some pediatric
endocrinologists believe that soy is a contributor.86 Of all the
estrogens found in the environment, soy is the likeliest explanation of
why African American girls reach puberty so quickly. Since its
establishment in 1974, the federal government's Women, Infants and
Children (WIC) program has provided free infant formula to teenage and
other low-income mothers while failing to encourage breastfeeding. Because
of perceived or real lactose intolerance, black babies are much more
likely to receive soy formula than Caucasian babies.
Early
maturation in girls heralds reproductive problems later in life, including
amenorrhea (failure to menstruate), anovulatory cycles (cycles in which no
egg is released), impaired follicular development (follicles failing to
mature and develop into healthy eggs), erratic hormonal surges, and other
problems associated with infertility. Because the mammary glands depend on
estrogen for their development and functioning, the presence of soy
estrogens at a susceptible time might predispose girls to breast cancer,
another condition that is on the rise and definitively linked to early
puberty.87
Recently, a
team of researchers headed by Brian L. Strom, MD, studied the use of soy
formula and its long-term impact on reproductive health. They announced
only one adverse finding: longer, more painful menstrual periods among
women who'd been fed soy formula in infancy.88 Dr. Strom's conclusion that
the results were "reassuring" made newspaper headlines all over the world,
though the data in the body of the report were anything but. Indeed, data
left out of the headlines and buried in the report revealed higher
incidences of allergies and asthma, and higher rates of cervical cancer,
polycystic ovarian syndrome, blocked fallopian tubes, and pelvic
inflammatory disease.89 Although thyroid damage from soy formula has been
the principal concern of critics for decades, the researchers excluded
thyroid function as a subject for study. Not surprisingly, this study was
funded in part by the infant-formula industry.
Most of the
fears concerning soy formula have focused on estrogens. There are other
problems as well, notably much higher levels of aluminum, fluoride, and
manganese than are found in either breastmilk or dairy formulas.90-96 All
three metals have the potential to adversely affect brain development.
Although trace amounts of manganese are vital to the development of the
brain, toxic levels accrued from ingestion of soy formula during infancy
have been found in children suffering from attention-deficit disorders,
dyslexia, and other learning problems.97, 98
Soy apologists
sometimes argue that the plant hormones in soy formula could not possibly
be harmful because Japanese women eat a lot of soy products and so must
have high levels of phytoestrogens in their breastmilk. Researchers,
however, have measured the soy isoflavones in breastmilk and found them
low even in vegetarian women who consume copious quantities of tofu, soy
milk, soy protein shakes, and other soy foods.99-101
Limited
evidence, however, suggests that vegetarian women who eat a lot of soy
foods during pregnancy may put their infants at risk in terms of their
future reproductive health, fertility, and possibly increased risk of
breast cancer. All of the problems that have befallen infants on soy
formula, as well as estrogen-related birth defects, have occurred (in
animal studies, at least) to the offspring of mothers who were given high
doses of soy during pregnancy.102 One of these birth defects that has been
linked to vegetarian diets in humans is hypospadias, a developmental
disorder in which the opening of the penis is located on the underside of
the shaft.103
Until soy
estrogens are definitely linked to reproductive-tract abnormalities,
infertility, and other health problems in humans, most health authorities
recommend that we "wait and see." This could be a terrible mistake.
In the 1940s
and 1950s, another estrogen, diethylstilbestrol (DES), was widely given to
Western women early in their pregnancies in a misguided attempt to prevent
miscarriage. That fact is relevant not only because DES bears a striking
structural similarity to some plant estrogens-including soy isoflavones-but
because it took more than 20 years before the full spectrum of harmful
effects was observed.104, 105
DES is 100,000
times more potent than soy phytoestrogens. However, the large quantities
of phytoestrogens in soy products are more than enough to counteract their
lower potency. When the effects of isoflavones in fetal and neonatal
animals have been studied, they have paralleled those observed in human
infants exposed to DES.106, 107 Recent studies indicate that the soy
isoflavone known as genistein may be even more carcinogenic than DES.108
Yet the belief
persists that soy hormones are "safe" because they are "weak" and
"natural." Although the soy industry has claimed that soy estrogens are
anywhere from 10,000 to 1,000,000 times weaker than the human estrogen
estradiol, the correct figure is only 1,200 times as weak.109 Though this
still sounds quite weak, it is not-because of the quantity of these
estrogens ingested by infants on soy formula, and by children and adults
who eat soy every day. These individuals consume far more soy estrogens
than were ever part of a traditional diet in Asia. The average isoflavones
intake in China is 3 milligrams, or 0.05 mg per kilogram of body weight.
In Japan, the figures range from 10 to 28 mg, or 0.17 to 0.47 isoflavones
per kg of body weight. In contrast, infants receiving soy formula
average 38 mg of isoflavones, which comes to a shocking 6.25 mg/kg of body
weight. Compare that dose to the 0.47 mg/kg per day fed to healthy
Japanese adult men and women who experienced thyroid suppression after
just three months-or to the 0.75 mg/kg of isoflavones fed to American
women who experienced hormonal changes sufficient to skew their menstrual
cycles after just one month.110 Although children and teenagers are
less vulnerable than infants, their young bodies are still developing, and
highly vulnerable to endocrine-system disruption by soy. And soy has been
shown to pass through the placentas of pregnant women to their unborn
babies.
Meanwhile, the
jury is still out on whether soy might help alleviate menopausal symptoms
or prevent osteoporosis and breast cancer. The soy industry's top
scientists, convened at the Fifth International Symposium on the Role of
Soy in the Preventing and Reversing Chronic Disease (held in Orlando,
Florida, September 21-24, 2003), conceded that the data are confusing and
contradictory, with some studies suggesting that soy might be helpful, and
others showing that soy contributes to osteoporosis and promotes breast
cancer.
What's certain
is that the levels of soy estrogens that might possibly have a beneficial
effect on hormonally related diseases have been proven to jeopardize the
health of the thyroid. Likewise, the 25 grams of soy protein per day
touted by the FDA to lower cholesterol (see sidebar, "Boon to the
Industry: The FDA's Soy Protein Health Claim") is very likely to harm the
thyroid, and thus increase one of the risk factors for heart disease.
The bottom
line is that the safety of soy foods has yet to be proven, and that human
beings have become guinea pigs in what Daniel M. Sheehan, formerly senior
toxicologist with the FDA's National Center for Toxicological Research,
has called a "large, uncontrolled and basically unmonitored human
experiment."111
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