F.Y.I. reposts: re: soy # 2 of 2

[Guest guest]

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WEB

Scientists Protest Soy

Approval

In Unusual Letter, FDA Experts Lay Out Concerns

Researchers Doerge and Sheehan, two

of the Food and Drug Administration’s experts on

soy, signed a letter of protest, which points to studies

that show a link between soy and health problems in

certain animals. The two say they tried in vain to stop

the FDA approval of soy because it could be

misinterpreted as a broader general endorsement

beyond benefits for the heart. The text of the letter

follows.

DEPARTMENT OF HEALTH

and HUMAN SERVICES

Public Health Service

Food and Drug Administration

National Center For Toxicological Research

Jefferson, Ark. 72079-9502

M. Sheehan, Ph.D.

Director, Estrogen Base Program

Division of Genetic and Reproductive Toxicology

and

R. Doerge, Ph.D.

Division of Biochemical Toxicology

February 18, 1999

Dockets Management Branch (HFA-305)

Food and Drug Administration

Rockville, MD 20852

To whom it may concern,

We are writing in reference to Docket # 98P-0683;

“Food Labeling: Health Claims; Soy Protein and

Coronary Heart Disease.” We oppose this health claim

because there is abundant evidence that some of the

isoflavones found in soy, including genistein and equol, a

metabolize of daidzen, demonstrate toxicity in estrogen

sensitive tissues and in the thyroid. This is true for a

number of species, including humans. Additionally, the

adverse effects in humans occur in several tissues and,

apparently, by several distinct mechanisms.

Genistein is clearly estrogenic; it possesses the

chemical structural features necessary for estrogenic

activity (; Sheehan and Medlock, 1995; Tong, et al,

1997; Miksicek, 1998) and induces estrogenic responses

in developing and adult animals and in adult humans. In

rodents, equol is estrogenic and acts as an estrogenic

endocrine disruptor during development (Medlock, et al,

1995a,. Faber and (1993) showed alterations

in LH regulation following developmental treatment with

genistein. Thus, during pregnancy in humans, isoflavones

per se could be a risk factor for abnormal brain and

reproductive tract development. Furthermore, pregnant

Rhesus monkeys fed genistein had serum estradiol levels

50- 100 percent higher than the controls in three different

areas of the maternal circulation (on, et al, 1998).

Given that the Rhesus monkey is the best experimental

model for humans, and that a women’s own estrogens are

a very significant risk factor for breast cancer, it is

unreasonable to approve the health claim until complete

safety studies of soy protein are conducted. Of equally

grave concern is the finding that the fetuses of genistein

fed

monkeys had a 70 percent higher serum estradiol level

than did the controls (on, et al, 1998). Development

is recognized as the most sensitive life stage for estrogen

toxicity because of the indisputable evidence of a very

wide variety of frank malformations and serious functional

deficits in experimental animals and humans. In the human

population, DES exposure stands as a prime example of

adverse estrogenic effects during development. About 50

percent of the female offspring and a smaller fraction of

male offspring displayed one or more malformations in the

reproductive tract, as well as a lower prevalence (about 1

in a thousand) of malignancies. In adults, genistein could

be a risk factor for a number of estrogen-associated

diseases.

Even without the evidence of elevated serum estradiol

levels in Rhesus fetuses, potency and dose differences

between DES and the soy isoflavones do not provide any

assurance that the soy protein isoflavones per se will be

without adverse effects. First, calculations, based on the

literature, show that doses of soy protein isoflavones used

in clinical trials which demonstrated estrogenic effects

were as potent as low but active doses of DES in Rhesus

monkeys (Sheehan, unpublished data). Second, we have

recently shown that estradiol shows no threshold in an

extremely large dose-response experiment (Sheehan, et

al, 1999), and we subsequently have found 31

dose-response curves for hormone-mimicking chemicals

that also fail to show a threshold (Sheehan, 1998a). Our

conclusions are that no dose is without risk; the extent of

risk is simply a function of dose. These two features

support and extend the conclusion that it is inappropriate

to allow health claims for soy protein isolate.

Additionally, isoflavones are inhibitors of the thyroid

peroxidase which makes T3 and T4. Inhibition can be

expected to generate thyroid abnormalities, including

goiter and autoimmune thyroiditis. There exists a

significant body of animal data that demonstrates

goitrogenic and even carcinogenic effects of soy products

(cf., Kimura et al., 1976). Moreover, there are significant

reports of goitrogenic effects from soy consumption in

human infants (cf., Van Wyk et al., 1959; Hydovitz,

1960; Shepard et al., 1960; Pinchers et al., 1965;

Chorazy et al., 1995) and adults (McCarrison, 1933;

Ishizuki, et al., 1991). Recently, we have identified

genistein and daidzein as the goitrogenic isoflavonoid

components of soy and defined the mechanisms for

inhibition of thyroid peroxidase (TPO)-catalyzed thyroid

hormone synthesis in vitro (Divi et al., 1997; Divi et al.,

1996). The observed suicide inactivation of TPO by

isoflavones, through covalent binding to TPO, raises the

possibility of neoantigen formation and because anti-TPO

is the principal autoantibody present in auto immune

thyroid disease. This hypothetical mechanism is consistent

with the reports of Fort et al. (1986, 1990) of a doubling

of risk for autoimmune thyroiditis in children who had

received soy formulas as infants compared to infants

receiving other forms of milk.

The serum levels of isoflavones in infants receiving soy

formula that are about five times higher than in women

receiving soy supplements who show menstrual cycle

disturbances, including an increased estradiol level in the

follicular phase (Setchell, et al, 1997). Assuming a

dose-dependent risk, it is unreasonable to assert that the

infant findings are irrelevant to adults who may consume

smaller amounts of isoflavones. Additionally, while there is

an unambiguous biological effect on menstrual cycle length

(Cassidy, et al, 1994), it is unclear whether the soy effects

are beneficial or adverse. Furthermore, we need to be

concerned about transplacental passage of isoflavones as

the DES case has shown us that estrogens can pass the

placenta. No such studies have been conducted with

genistein in humans or primates. As all estrogens which

have been studied carefully in human populations are

two-edged swords in humans (Sheehan and Medlock,

1995; Sheehan, 1997), with both beneficial and adverse

effects resulting from the administration of the same

estrogen, it is likely that the same characteristic is shared

by the isoflavones. The animal data is also consistent with

adverse effects in humans.

Finally, initial data fi-om a robust (7,000 men)

long-term (30+ years) prospective epidemiological study

in Hawaii showed that Alzheimer’s disease prevalence in

Hawaiian men was similar to European-ancestry

Americans and to Japanese (White, et al, 1996a). In

contrast, vascular dementia prevalence is similar in Hawaii

and Japan and both are higher than in European-ancestry

Americans. This suggests that common ancestry or

environmental factors in Japan and Hawaii are responsible

for the higher prevalence of vascular dementia in these

locations. Subsequently, this same group showed a

significant dose-dependent risk (up to 2.4 fold) for

development of vascular dementia and brain atrophy from

consumption of tofu, a soy product rich in isoflavones

(White, et al, 1996b). This finding is consistent with the

environmental causation suggested from the earlier

analysis, and provides evidence that soy (tofu)

phytoestrogens causes 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 (Irvine, 1998),

there is a mechanistic basis for the human findings. Given

the great difficulty in discerning the relationship between

exposures and long latency adverse effects in the human

population (Sheehan, 1998b), and the potential

mechanistic explanation for the epidemiological findings,

this is an important study. 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, and thus the

results should be interpreted in this context.

Does the Asian experience provide us with

reassurance that isoflavones are safe? A review of several

examples lead to the conclusion “Given the parallels with

herbal medicines with respect to attitudes, monitoring

deficiencies, and the general difficulty of detecting

toxicities with long Iatencies, I am unconvinced that the

long history of apparent safe use of soy products can

provide confidence that they are indeed without risk.”

(Sheehan, 1998b).

It should also be noted that the claim on p. 62978 that

soy protein foods are GRAS is in conflict with the recent

return by CFSAN to Archer s Midland of a petition

for GRAS status for soy protein because of deficiencies in

reporting adverse effects in the petition. Thus GRAS

status has not been granted. Kahl can provide you

with details. It would seem appropriate for FDA to speak

with a single voice regarding soy protein isolate.

Taken together, the findings presented here are

self-consistent and demonstrate that genistein and other

isoflavones can have adverse effects in a variety of

species, including humans. Animal studies are the front line

in evaluating toxicity, as they predict, with good accuracy,

adverse effects in humans. For the isoflavones, we

additionally have evidence of two types of adverse effects

in humans, despite the very few studies that have

addressed this subject. 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 (Sheehan and Medlock,

1995; Sheehan, 1997). The health labeling of soy protein

isolate for foods needs to considered just as would the

addition of any estrogen or goitrogen to foods, which are

bad ideas.

Estrogenic and goitrogenic drugs are regulated by

FDA, and are taken under a physician’s care. Patients are

informed of risks, and are monitored by their physicians

for evidence of toxicity. There are no similar safeguards in

place for foods, so the public will be put at potential risk

from soy isoflavones in soy protein isolate without

adequate warning and information.

Finally, NCTR is currently conducting a long-term

multigeneration study of genistein administered in feed to

rats. The analysis of the dose range-finding studies are

near-complete or complete now. As preliminary data,

which is still confidential, maybe relevant to your decision,

I suggest you contact Dr. Barry Delclos at the address on

the letterhead, or email him.

Sincerely,

M. Sheehan

R. Doerge

Enclosures

cc: Dr. Bernard Schwetz, Director, NCTR

Dr. Barry Delclos

REFERENCES

Cassidy, A, Bingham, S, and Setchell, KDR. Biological

effects of soy protein rich in isoflavones on the menstrual

cycle of premenopausal women. Am. J. Clin. Nutr. 60,

333- 340, 1994.

Chorazy, P.A., Himelhoch, S., Hopwood, N, J., Greger,

N. G., and Postellon, D.C. Persistent hypothyroidism in

an infant receiving a soy formula: Case report and review

of the literature. Pediatrics 148-150, 1995.

Divi, R. L., Chang, H. C., and Doerge, D.R.

Identification, characterization and mechanisms of

anti-thyroid activity of isoflavones from soybean.

Biochem. Pharrnacol. 54, 1087-1096, 1997.

Divi, R.L. and Doerge, D.R. Inhibition of thyroid

peroxidase by dietary flavonoids. Chem. Res. Toxicol. 9,

16-23, 1996.

Levy, JR, Faber, FA,Ayyash, L, and , CL. The

effect of prenatal exposure to phytoestrogen genistein on

sexual differentiation in rats. Proc. Sot. Exp. Biol. Med.

208, 60-66, 1995.

Fort, P., Lanes, R., Dahlem, S., Reeker, B.,

Weyman-Daum, M., Pugliese, M., and Lifshitz, F. Breast

feeding and insulin-dependent diabetes mellitus in children.

J. Am. Coil. Nutr. 5,439-441, 1986.

Fort, P, Moses, N., Fasano, M, Goldberg, T, and

Lifshitz, F. Breast and soy-formula feedings in early

infancy and the prevalence of autoimmune thyroid disease

in children. J. Am. Coil. Nutr. 9, 164-167, 1990.

on, R. M.. pi, P. P., and Henson, M.C.

Effects of genistein on estradiol production in pregnant

Rhesus monkeys (A4acaca Mulatta). Am. J. Primatology

45, 183, 1998.

Hydovitz, JD, Occurrence of goiter in an infant on a soy

diet. New Eng. J. Med. 262, 351-353, 1960.

Irvine, CHG, Fitzpatrick, MG, and , SL.

Phytoestrogens in soy-based infant foods: Concentrations,

daily intake, and possible biological effects. Proc. Sot.

Exp. Biol. Med. 217,247-253, 1998.

Ishizuki, Y., Hirooka, Y., Murata, Y., and Togasho, K.

The effects on the thyroid gland of soybeans administered

experimentally to healthy subjects. Nippon Naibunpi

gakkai Zasshi 67,622-629, 1991.

Kimura, S, Suwa, J, Ito, B and Sate, H. Development of

malignant goiter by defatted soybean with iodine-free diet

in rats. Gann 67, 763-765, 1976.

McCarrison, R. The goitrogenic action of soybean and

groundnut. Indian J. Med. Res. 21, 179-181, 1933.

Medlock, K. L., Branham, W. S., Sheehan, D.M. The

effects of phytoestrogens on neonatal rat uterine growth

and development. Proc. Sot. Exp. Biol. Med.

208:307-313, 1995.

Medlock, K.L., Branham, W. S., Sheehan, D.M. Effects

of coumestrol and equol on the developing reproductive

tract of the rat. Proc. Sot. Exp. Biol. Med., 208:67-1,

1995. Miksicek, RJ. Estrogenic flavonoids: Structural

requirements for biological activity. Proc. Sot. Exp. Biol.

Med. 208,44-50, 1995.

Pinchers, A, MacGillivray, MH, Crawford, JD, and

Freeman, AG. Thyroid refractoriness in an athyreotic

cretin fed soybean formula, New Eng. J. Med., 265,

83-87, 1965.

Setchell, KDR, Zimmer-Nechemias, L, Cai, J, and Heubi,

JE. Exposure of infants to phyto-estrogens from

soy-based infant formula. Lancet, 350,23-27, 1997.

Sheehan, D.M. Literature analysis of no-threshold

dose-response curves for endocrine disrupters.

Teratology, 57,219, 1998a.

Sheehan, D.M. Herbal medicines and phytoestrogens:

risklbenefit considerations. Proc. Sot. Exp. Biol. Med.,

217,379-385, 1998b.

Sheehan, D.M. Isoflavone content of breast milk and soy

formulas: Benefits and risks. Clin. Chem., 43:850, 1997.

Sheehan, D.M. and Medlock, K.L. Current issues

regarding phytoestrogens. Polyphenols Actualities,

13:22-24, 1995.

Sheehan, D. M., Willingham, E., Gaylor, D., Bergeron, J.

M., and Crews, D. No threshold dose for

oestradiol-induced sex reversal of turtle embryos: How

little is too much? Environmental Health Perspectives,

February, 1999 issue, in press.

Shepard, TH, Pyne, GE, Kirschvink, JF, and McLean,

CM. Soybean goiter. New Eng. J. Med. 262,

1099-1103, 1960.

Tong, W, Perkins, R, Xing, L, Welsh, WJ, and Sheehan,

DM. QSAR models for binding of estrogenic compounds

to estrogen receptor alpha and beta subtypes. Endo. 138,

4022- 4025, 1997. Van Wyk, JJ, Arnold, MB, Wynn, J,

and Pepper, F. The effects of a soybean product on

thyroid function in humans, Pediatrics 24,752-760, 1959.

White, L, Petrovitch, H, Ross, GW, and Masaki.

Association of mid-life consumption of tofu with late life

cognitive impairment and dementia: The Honolulu-Asia

Aging Study. The Neurobiol. of Aging, 17 (suppl 4), S

121, 1996a.

White, L, Petrovich, H, Ross, GW, Masaki, KH, Abbot,

RD, Teng, EL, , BL, Blanchette, PL, Havlik,

RJ, Wergowske, G, Chiu, D, Foley, DJ, Murdaugh, C,

and Curb, JD. Prevalence of dementia in older

Japanese-American men in Hawaii, JAMA 276,

955-960, 1996b.

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-------------- NOTES FROM MARY ---------------

I've written about soy before, and how the overconsumption of soy

products - this current craze for more and more isoflavone pills and

powders - can contribute to thyroid problems. (See " The

Downsides of Soy, " at

http://thyroid.about.com/library/weekly/aa083099.htm). I eat some

soy foods myself, but won't touch isoflavone supplements or soy

protein powders because of concern for my thyroid health. Now,

even the U.S. Food and Drug Administration is questioning whether

the current soy craze is entirely healthy. From a new FDA Report:

" 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 risks. " Read this excellent

pro and con overview of soy products, at: " Soy: Health Claims for

Soy Protein, " http://www.fda.gov/fdac/features/2000/300_soy.html

Even more questions about soy are popping up. Here's a quote

from FoxNews. . . " Because phytoestrogens sometimes act like a

hormone, they have the potential to produce health benefits -- but

there are also potential dangers. There's always a trade-off; there's

no free lunch. . . We're not talking just about nutrients, but

pharmacological agents which have the opportunity to adjust the

metabolism of our cells. " Quoted from " Soy Is Heralded by

Nutrition Experts, But Not Without Concerns, " located at

http://www.foxnews.com/health/042800/soysick.sml

& & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & & &

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Soy Online Service

Thyroid Disease: The Dangerous Downside of Soy Products

Dateline: 08/30/99

It seems that there's isn't a newspaper, magazine or

news program that hasn't recently featured a story on

the amazing health benefits of soy food products and

soy/isoflavone supplements. Soy is promoted as a

healthy alternative to estrogen replacement for some

women, as a possibly way to reduce the risk of breast

cancer, as a way to minimize menopause symptoms, and as

a healthier, low-fat protein alternative for

meats and poultry. But what all the positive stories

fail to mention is that there is a very real -- but very

overlooked -- downside to the heavy or long-term use of

soy products.

Soy products increase the risk of thyroid disease. And

this danger is particularly great for infants on soy

formula.

This is not information that the powerful and

profitable U.S. soy industry wants you to know. The sale of

soy products is big business, and the increasing demand

for soy protein products, soy powders and soy

isoflavone supplements is making that an even more

profitable business than ever before.

In researching my upcoming book, which covers the issue

of soy products and the thyroid in great depth, I

talked to Dr. Mike Fitzpatrick, an environmental

scientist and phytoestrogen researcher who has

conducted in-depth studies on soy, particularly the use

of soy formulas. Dr. Fitzpatrick makes it clear that

soy products can have a detrminental affect on both

adults and infants. In particular, he firmly believe that

soy formula manufacturers should remove the isoflavones

-- that part of the soy products that act as

anti-thyroid agents -- from their products.

Researchers have identified that the isoflavones act as

potent anti-thyroid agents, and are capable of

suppressing thyroid function, and causing or worsening

hypothyroidism. Soy is a phytoestrogen, and

therefore acts in the body much like a hormone, so it's

no surprise that it interacts with the delicate balance

of the thyroid's hormonal systems. High consumption of

soy products are also proven to cause goiter,

(Anti-thyroid isoflavones from soybean: isolation,

characterization, and mechanisms of action, Divi

RL; Chang HC; Doerge DR, National Center for

Toxicological Research, Jefferson, AR 72079, USA,

Biochem Pharmacol, 1997 Nov, 54:10, 1087-96)

Note: The best source of information on soy and its

negative impact on health can be found at the Soy

Online Service, and in particular, its page on

phytoestrogenic effects of soy, and impact on the

thyroid.

Isoflavones belong to the flavonoid or bioflavonoid

family of chemicals, and are considered endocrine

disruptors -- plants or other products that act as

hormones, disrupting the endocrine system, and in some

cases, this disruption involves acting as an

anti-thyroid agent. (The grain millet, for example, contains high

levels of flavonoids, and is commonly known as

problematic for thyroid function). Flavonoids inhibit thyroid

peroxidase (TPO), which disturbs proper thyroid

function.

The March 1999 issue of Natural Health magazine has a

feature on soy that quotes R. Doerge,

Ph.D., a researcher at the Food and Drug

Aministration's National Center for Toxicological Research. Dr.

Doerge has researched soy's anti-thyroid properties,

and has said " ...I see substantial risks from taking soy

supplements or eating huge amounts of soyfoods for

their putative disease preventive value. There is

definitely potential for interaction with the thyroid. "

One UK study of premenopausal women gave 60 grams of

soy protein per day for one month. This was

found to disrupt the menstrual cycle, with the effects

of the isoflavones continuing for a full three months

after stopping the soy in the diet. Isoflavones are

also known to modify fertility and change sex hormone

status. Isoflavones have been shown to have serious

health effects -- including infertility, thyroid disease or

liver disease -- on a number of mammals.

Dr. Fitzpatrick believes that people with

hypothyroidism should avoid soy products, because, " any

inhibition of TPO will clearly work against anyone

trying to correct an hypothyroid state. " In addition, he

believes that the current promotion of soy as a health

food will result in an increase in thyroid disorders.

The Dangers of Soy Formulas

Since the late 1950's, it has been known that soy

formulas contain anti-thyroid agents. Infants on soy

formula are particularly vulnerable to developing

autoimmune thyroid disease when exposed to high

exposure of isoflavones over time. ( Breast and

soy-formula feedings in early infancy and the

prevalence of autoimmune thyroid disease in children.

Fort P; Moses N; Fasano M; Goldberg T;

Lifshitz F Department of Pediatrics, North Shore

University Hospital-Cornell University Medical College,

Manhasset, New York 11030. J Am Coll Nutr, 1990 Apr,

9:2, 164-7) This study found that the

frequency of feedings with soy-based milk formulas in

early life was noticeably higher in children with

autoimmune thyroid disease, and thyroid problems were

almost triple in those soy formula-fed children

compared to their siblings and healthy unrelated

children. Dr. Fitzpatrick even believes that long-term

feeding with soy formulas inhibits TPO to such an

extent that long-term elevated TSH levels can also raise

the risk of thyroid cancer.

Not much is being done in the U.S. to make parents

aware of the thyroid-related dangers of soy formulas,

or to alert the public that heavy soy consumption may

be a danger to thyroid function. Other countries,

however, are far ahead of the U.S. In July of 1996, the

British Department of Health issued a warning that

the phytoestrogens found in soy-based infant formulas

could adversely affect infant health. The warning

was clear, indicating that soy formula should only be

given to babies on the advice of a health professional.

They advised that babies who cannot be breastfed or who

have allergies to other formulas be given

alternatives to soy-based formulas.

Why more information is not available about these

concerns is probably a function of the tremendous

strength of the large agricultural companies that

dominate America's soy market. One thing is clear,

however. At the same time that health experts, and

nearly every radio and television health program in the

nation touts soy as the miracle health food of the new

millenium, the United States pediatric and medical

community needs to get more on top of this issue, and

begin to counsel their patients regarding the serious

impact use of soy products can have on thyroid

function.

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

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. For more information on how

much soy is too much, see the Soy Online Service

guidance page.

The USDA has launched a website that is promoting the

health benefits of use of soy and soy foods. The

USDA site lists the isoflavone content of a total of

128 foods, including foods such as vegetarian hot dogs

soybeans, chickpeas and tofu. This can help you in

deciding how much soy to include in your diet.

More information

For more information on soy products, see:

Soy Online Service

Soy's Negative Impact on The Thyroid: Thyroid

Disease Net Links, a comprehensive listing I've

developed

All About Soy, About.com's Nutrition Guide Rick

Hall's excellent list of soy-related resources

Food and Drug Administration Approves New Health

Claim for Foods Containing Soy, October

1999 article discussing this FDA approval, from

About.com Nutrition Guide, Rick Hall.

Concerns Regarding Soybeans, from the Rheumatic

Diseases website

Are Soy Products Dangerous?, from the Gerson

Healing Newsletter, Vol. 11, No. 5, Sep./Oct.

1997

About.com's Vegetarian Guide covers " The Joy of

Soy "

Guide to Soy Isoflavones

Soy to the World: A Guide to Incorporating Soy

into Your Diet

________________________________________________________________

SOS Guidance

What we think you should be doing about

phytoestrogens and soy.

How much soy is safe to eat?

For infants, we believe any soy is too much soy. Adults consuming soy

should also exercise caution.

The observations from the Ishizuki Thyroid Clinic study indicate

significant, goitrogenic effects in subjects fed 30 g

soybeans per day. Based on the concentrations of isoflavones found in

Japanese soybeans, 30 g of soybeans

could contribute up to 23 mg total genistein and 10 mg of total daidzein.

For a 70 kg adult this would equate to an

intake of 0.33 mg/kg-body weight of genistein and 0.14 mg/kg-body weight

of daidzein per day.

This amount of isoflavone consumption is approximately three times higher

than the amount typically consumed in

Japan, which is 0.08 to 0.13 mg/kg-body weight of total genistein per day

for a 70 kg adult.

For infants fed soy-formulas, the exposure to isoflavones is greater than

in any other population group. Infants less

than 6 months of age who are solely fed soy formula have an intake of up

to 5.4 mg/kg-body weight of genistein

and 2.3 mg/kg-body weight basis of daidzein per day. Hence, soy formula

fed infants are exposed to

approximately 16 times greater levels of isoflavones than the subjects in

the Ishizuki study.

The concentrations of isoflavones found in soy products can vary but

studies from New Zealand indicate that a

diet of 500g of soy milk plus 200g tofu per day would result in the

consumption of up to 135 mg total genistein and

80 mg total daidzein. For a 70 kg adult this equates to an intake of 1.9

mg/kg-body weight of genistein and 1.1

mg/kg-body weight of daidzein per day. This degree of exposure to

isoflavones is more than five times that of

subjects in the investigation by Ishizuki.

Users of isoflavone supplements may consume up to 40 mg of genistein per

day. For a 70 kg adult this is

equivalent to 0.57 mg/kg-body weight basis of genistein per day which is

about 1.7 times more than that found to

have goitrogenic effects.

Therefore, soy formula fed infants, high soy consumers and users of

isoflavone supplements might exhibit classic

hypothyroid symptoms without recognising a dietary connection.

Unfortunately there is little data as what

constitutes an appropriate level of soy intake, although it appears that

some western consumers may now be

eating far greater amounts of soy than that taken as part of a traditional

Asian diet.

Soy users should be aware of the potency of just 30 mg soy isoflavones per

day. Thyroid disorders (see above for

discussion on the active dose in the Ishizuki Thyroid Clinic study) and

other biological effects have been observed

at dose around this level.

As an approximate guide 30 mg of soy isoflavones can be found in:

Soybeans and soyflours: 9 - 20g (0.3 - 0.7oz).

Soy mince: 12g (0.4oz).

Tofu: 50 - 110g (1.8 - 3.9oz).

Soy milks: 150 - 240g (5.3 - 8.5oz).

Miso: 35 - 45g (1.2 - 1.6oz).

Soybean sprouts: 80g (2.8oz).

What products contain soy?

As well as obvious soyfoods like tofu, soy milk and miso, and other soy

products such as isolated soy protein

(ISP) and soy protein concentrate (SPC), very many processed foods contain

soy, some examples are:

Biscuits

Breads

Vegetarian

burgers

Cakes

Crackers

Bakery

products

Pastries

Meat substitutes

Pancakes

Chicken nuggets

Legume meal

Fish fingers

Pies

Meat extenders

Hydrolysed

vegetable protein (HVP)

Yoghurt

Breakfast cereals

Sausages

Soups

Baby foods

Doughnuts

Vegetarian meats

Sandwich spreads

Baby rusks

Pet Foods

Animal feeds

Textured

vegetable protein (TVP)

Why isn't this information readily available?

People deserve the right to know about what they are eating and what they

are feeding their children. So why are

government agencies so reluctant to share information with the public?

New Zealand environmental scientist and phytoestrogen researcher Dr Mike

Fitzpatrick met with California DHS

staff in June 1998 to express his concerns about soy, and particularly soy

formulas. He received a written

response from DHS toxicologist Dr Loscutoff. Loscutoff stated:

" I agree that high levels of dietary exposures to isoflavones in infants

fed soy-based formulas is cause for

concern " .

" I do not agree that parents have a right to know that soy-based formulas

contain isoflavones and the kinds of

toxicities isoflavones might demonstrate in infants, since parents would

not know how to interpret the information. "

This kind of response it quite typical of agencies fearing a severe

backlash from the soy lobby should they alert

the public to the potential health concerns of soy isoflavones.

What else can I do?

Write to your National or State Health Department representatives

demanding information on the risks associated

with the consumption of soy isoflavones, especially by infants, and the

safety of isoflavone

supplements/OTC-drugs.

Write to potentially sympathetic politicians (e.g. in the US Senator

Barbara Boxer or Senator Fred Lautenberg),

and express your concern about the presence of isoflavones in soy

formulas. Ask for clarification regarding the

safety of soy formulas and soy isoflavone supplements/OTC drugs.

Share this information with your health professionals and friends.

Be prepared for a 'no evidence of harm' response from government agencies.

The facts, however, tell a different

story.

Support our work. Contact Soy Online Service if you can help.

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