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Low Testosterone, Early Death?
Higher Death Risk in Men With Lower Testosterone Levels
By Daniel J. DeNoon
WebMD
Health NewsReviewed by Louise Chang, MDNov. 27, 2007 -- The lower a man's testosterone level, the higher his risk of death
-- especially death from heart disease.
The finding comes from a study of British men aged 40 to 79 by University of Cambridge gerontologist Kay-Tee Khaw, MBBCh,
and colleagues.
"The men with lower testosterone levels had an increased risk of dying from any cause, but most particularly of cardiovascular
disease," Khaw tells WebMD. "We looked at cancer, too, and found no evidence of a link to cancer with higher testosterone
levels."
Nearly 12,000 men enrolled in the long-term study from 1993 to 1997. More than 800 of the men died by 2003; Khaw compared
these men's testosterone levels to those of some 1,500 living study participants.
After adjusting for factors that might affect risk of death -- including age, weight, smoking, alcohol use, high blood
pressure, diabetes, physical activity, education, and social class -- the link between low testosterone and earlier death
remained.
Compared to men with the lowest quartile (25%) of testosterone levels:
Men in the second lowest quartile were 25% less likely to die.
Men in the second highest quartile were 38% less likely
to die.
Men in the highest quartile were 41% less likely to die.
"We found that low testosterone predicts early mortality
in men over the next 10 years or so," Khaw says. "But we think this finding needs to be replicated. We would like others to
look at this in other populations of men and see if they get the same results."
The findings make sense to Robert Davis, MD, professor of urology at the University of Rochester, N.Y. Davis says low
testosterone is common among men with metabolic syndrome -- a constellation of risk factors including abdominal fat, high
blood sugar, high blood pressure, low HDL cholesterol, and high blood-fat levels.
"Certainly I'm not surprised at this finding. It's been shown that low testosterone correlates with metabolic syndrome,
which is related to diseases like diabetes, heart disease, and vascular disease," Davis tells WebMD. "The need to check testosterone
levels in people with metabolic syndrome is being recognized more and more among physicians."
Testosterone Therapy: Studies Needed
Low testosterone may be bad, but it is not clear that testosterone replacement
therapy corrects this problem. Only clinical trials can prove whether testosterone supplementation can lower the risk of death
linked to low testosterone levels. Ironically, researchers have been reluctant to test testosterone replacement in clinical
trials because of worries that the treatment may increase men's risk of prostate cancer.
"Our study may provide some reassurance of those planning trials of testosterone supplementation," Khaw says. "The irony
is that while a lot of men believe testosterone supplements may be good for their health, those trials have not been done
because of ethical concerns of testosterone causing prostate cancer."
Davis worries that doctors are too wary of prescribing testosterone supplements for men with too-low testosterone levels.
"It is a very underdiagnosed and undertreated problem," he says. "One of the myths is that androgen supplementation will
cause a cancer. We know that prostate cancer often regresses when androgen is removed, but there is very little evidence that
supplementing to normal levels increases risk of cancer, and some evidence it may lower it."
Khaw and colleagues report their findings in the Dec. 4 issue of the journal Circulation.
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Clinical and biologic activity of soy protein powder (SPP) in healthy male volunteers: Effect on testosterone and luteinizing
hormone (LH).
S. Goodin, F. Shen, W. Shih, N. Dave', M. Kane, G. Lambert, M. Gallo, R. Dipaola;
Cancer Institute of New Jersey, New Brunswick, NJ; UMDNJ/Robert Wood Johnson Medical School, Piscataway, NJ
Abstract: Background: Epidemiologic studies and a recent prospective trial have revealed a reduced risk of prostate cancer
associated with consumption of soy foods, possibly due to the estrogenic properties of soy.
To determine if a commonly used SPP can have estrogenic activity in men, we specifically evaluated supplementation with
SPP in healthy male volunteers and the effect on testosterone and LH.
Methods: Healthy volunteers recruited to this study were men 18 years of age or older that were in good health with no
known allergy to soy or phenylalanine. Treatment consisted of consuming two scoops (56g) of pure SPP (Puritan's Pride, Oakdale,
New York) daily for 28 days.
Serum testosterone and LH levels were collected prior to initiation of supplementation with soy protein powder, throughout
the 28 days, and 14 days after the completion of therapy. Patients maintained a food diary throughout the 28-day period.
Results: Twelve healthy volunteers were enrolled with a mean age of 32 years (range 25 to 47). Serum testosterone concentrations
decreased during the 4-week use of SPP and increased within two weeks after SPP was discontinued, with a statistically significant
percent change in testosterone over the four-week period (P=0.021).
At no time did the mean serum testosterone fall below the normal reference range. Serum LH concentrations decreased during
the 4 week use of soy protein powder then increased within two weeks after soy protein powder was discontinued but the changes
did not reach statistical significance (P =0.20).
There were no side effects reported by any participants. Using a yeast based assay transfected with the alpha and beta
estrogen receptor (ER), we found that the soy protein selectively activated ER-beta.
Conclusions: Soy protein powder decreases testosterone levels in healthy patients, which is reversible upon removal of
SPP from the diet.
These data support further study of these hormonal effects as a mechanism in prostate cancer prevention.
Abstract No: 4611
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A Global warming data manipulation style of spin may have started
kicking in:
10/15/2009 I have a question regarding substituting soy for milk products. Doctor has a 7 month old patient he has diagnosed
with milk induced colitis vs. milk allergy. He is being breast fed so the Doctor is suggesting she avoid milk in her diet
and substitute with soy. She is concerned about the effect of soy on male hormones. I have not been able to locate any information
to guide her at this time and was wondering if you could give me information to pass on to this mother. He has improved greatly
on a milk free diet. Thank you for your time and attention to this matter.
Thank you for your recent inquiry.
Unfortunately, I am not going to be able to give you a definitive answer. There is a rich body of literature looking
at the effect of soy on various aspects of human physiology. There has been no study in humans, however, that relates to infant
feeding. Perhaps the most relative article related to feeding was performed in Marmoset monkeys. For your interest, an abstract
of this study is copied for you below. The study itself does give some caution regarding the administration of soy to infants.
However, on the "flip side" of this issue, soy substitution for milk has been standard therapy in this country for many years,
and I could find no reports in humans which substantiate any adverse effect on sexual development in males. It would be expected,
should such have occurred, it would have been reported.
Also offering some consolation is another review of reports of soy in male adults. Their study found no significant effect.
I have also copied the abstract for that article below as well.
A review in the Journal of Pediatric Endocrinology and Metabolism (abstract also copied below) reached a conclusion that
we are not able at this time to adequately assess the effect of phytoestrogens in soy in children who drink soy milk. There
are only, according to this investigation, "limited data available concerning potential benefits or adverse effects."
In summary, as stated above, there is no definitive answer to your question, and the decision as to whether or not this
child should take soy will have to be made on the basis of a personal assessment of the risk/benefit ratio. However, it might
give you and the mother of this child some solace to reflect upon the fact that soy has been used in this country in thousands
of children over the last two decades as a substitute for milk. It would seem, should there be any significant adverse effect
of this supplement, there would have been case reports of these untoward effects. I was not able to find any such evidence.
Thank you again for your inquiry. Although the answer to your question is not definitive, I hope this information is
of help to you and the parent in making your decision.
Abstract 1:
Review finds no effect of soy on testosterone
By Caroline Scott-Thomas, 30-Jun-2009
Related topics:
Quality & Safety
A review of 15 studies into the influence of soy proteins or isoflavones on male hormones has found
no evidence of an estrogen-like effect.
Soy has garnered attention as a healthy source of protein, and has been linked
to a multitude of health benefits, including protection from breast cancer, prostate cancer, menopausal symptoms and heart
disease. But some studies have suggested that soy isoflavones could affect male testosterone levels, due to their similarity
in chemical structure to estrogen, which means they bind to estrogen receptors and can exert estrogen-like effects.
The
meta-analysis of data was carried out by researchers at the University of Minnesota who wrote: “Because of the increasing
popularity of soy foods and the availability of isoflavone supplements, there is an important public health need to understand
the impact of soy isoflavones on reproductive hormone levels in men.”
Low levels of testosterone in men can lead
to depressed mood, loss of muscle mass, weight gain, erectile dysfunction and osteoporosis.
‘No significant effects’
Although two of the studies examined did assert that testosterone levels were lowered as a result of soy consumption,
the authors wrote: “No significant effects of soy protein or isoflavone intake on T [testosterone] or SHBG [sex hormone-binding
globulin] were detected…There was no significant pooled effect of isoflavone consumption on the hormonal profile, T
and SHBG.”
Contradictory studies
Furthermore, the authors criticized the studies that reported lowered testosterone
levels for their methodology. (Source: Food production daily.com)
Abstract 2:
Human Reproduction, Vol. 17, No. 7, 1692-1703, July 2002
© 2002 European Society of Human Reproduction
and Embryology
Infant feeding with soy formula milk: effects on the testis and on blood testosterone levels in marmoset
monkeys during the period of neonatal testicular activity
Richard M. Sharpe,1, Bronwen Martin, Keith Morris, Irene Greig,
Chris McKinnell, Alan S. McNeilly and Marion Walker
MRC Human Reproductive Sciences Unit, Centre for Reproductive Biology,
37 Chalmers Street, Edinburgh EH3 9ET, UK
BACKGROUND: This study has addressed concerns about possible effects of feeding
human infants soy formula milk (SFM). METHODS: This is a feeding study in marmosets, using a mainly co-twin design. From 4–5
until 35–45 days of age, co-twin males were fed by hand with either standard (cow) formula milk (SMA = controls) or
with SFM for ~8 h each day (2 h at weekends) and intake related to bodyweight. Blood samples were collected at 18–20
and at 35–45 days of age in 13 sets of co-twins plus two non-twin males per group and, at the later age, seven sets
of co-twins were killed and the testes and pituitary gland fixed for cell counts. RESULTS: Weight gain and formula intake
were similar in both feeding groups. SMA-fed males had mean testosterone levels of 2.8–3.1 ng/ml, typical of the ‘neonatal
testosterone rise’, whereas SFM-fed males exhibited consistently lower mean levels (1.2–2.6 ng/ml); paired comparison
in SMA-and SFM-fed co-twins at day 35–45 revealed 53–70% lower levels in 11 of 13 co-twins fed with SFM (P = 0.004).
Further evidence for suppression of testosterone levels in SFM-fed males came from comparison of the frequency of low testosterone
levels (<0.5 ng/ml). In historical controls aged 35–45 days, two out of 22 values were <0.5 ng/ml, a similar frequency
as found in control SMA-fed males (one out of 15 values <0.5 ng/ml). In contrast, 12 out of 15 values for SFM-fed males
were <0.5 ng/ml (P < 0.001). There was no consistent relationship between SFM intake/g and testosterone levels. Paradoxically,
the mean number of Leydig cells per testis was increased by 74% (P < 0.001) in co-twins fed SFM, when compared with their
SMA-fed brothers, whereas no significant changes were found in numbers of Sertoli and germ cells. Because of the lack of gonadotrophin
assays, the number of immunopositive LHß and FSHß cells in the pituitary gland, and their ratio, were determined but no consistent
difference was found between SMA- and SFM-fed twins. CONCLUSIONS: Based on the average isoflavone content of the SFM brand
used, intake of isoflavones was estimated at 1.6–3.5 mg/kg/day in the SFM-fed marmosets which is 40–87% of that
reported in 4 month human infants fed on a 100% SFM diet. It is therefore considered likely that similar, or larger, effects
to those shown here in marmosets may occur in human male infants fed with SFM. Whether the changes described result in longer-term
effects is under investigation.
Abstract 3:
J Pediatr Endocrinol Metab. 2002 May;15(5):561-72. Links
Phytoestrogens: a review of recent findings.
Stark
A, Madar Z.
Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot,
Israel.
Phytoestrogens have been investigated at the epidemiological, clinical and molecular levels to determine their
potential health benefits. The two major groups of phytoestrogens, isoflavones and lignans, are abundant in soy products and
flax respectively, but are also present in a variety of other foods. It is thought that these estrogen-like compounds may
protect against chronic diseases, such as hormone-dependent cancers, cardiovascular disease and osteoporosis. Furthermore,
phytoestrogens are used as a natural alternative to hormone replacement therapy and to reduce menopausal symptoms. Phytoestrogens
have been shown to induce both estrogenic and anti-estrogenic effects but their biological relevance and potency have not
been well characterized. In children, consumption of soy-based formulas and soy milk can lead to high levels of exposure to
phytoestrogens with only limited data available concerning potential benefits or adverse effects. Phytoestrogens are considered
good candidates for use in natural therapies and as chemopreventive agents in adults. Safe and efficacious levels have yet
to be established.
Sincerely,
Phil Lieberman, M.D.
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Here's a bit from folks who would know how soy affects that basic
function of a man:
Soy is Still Bad Protein
by Glen Neilson
We first published an article about how soy protein is estrogenic, can lower Testosterone counts, and can even kill testicular
cells in January of 2000. We then published new research on the matter in February of 2001. But you know something? The national
media still won't touch the story. You can pick up the "Food" section of practically any local newspaper and see glowing reviews
of the healthy attributes of soy protein, complete with yummy, Testosterone-lowering recipes.
Likewise, the other weightlifting and bodybuilding mags still tout its benefits, and a week doesn't go by that we don't
get a letter from some irate soy fan who ends up questioning our parentage.
Given all that, we think that the topic deserves to be visited again and again until every man, woman, and child knows
the truth. Hence this new article on soy. Oh, and make sure you read the letter that follows the article. It was written by
two of the Food and Drug Administration's soy experts who attempted to stop FDA approval of soy.
There's a lot of talk today about soy. Turn on the news and its soy, read a diet book and you'll find soy, go to
your local gym and a personal trainer will recommend soy. What is it about soy that has captivated this nation? Well for starters
it has many health benefits backed up by good science, it's inexpensive, it has a good track record in Asia, and the government
has allowed a seal of approval to be stamped on food items that contain 6.25 grams of soy protein.
Sounds like soy is a "can't miss" product, but is it? In this article we'll uncover the darker side of supposedly innocent
soy and show you why you might not choose to include it in your otherwise healthy diet.
Many papers have exhorted the benefits of soy, but as the saying goes "if it sounds too good to be true, it probably
is" fits soy better than anything else you might imagine.
Science has shown soy, more importantly its phyto-estrogen components, namely genistein, has the ability to attach to
estrogen receptor sites and through transcription, act as female hormones such as estradiol. This, in some cases, can have
benefits so it's not strange that soy would receive some well-deserved attention. The problem with this attention is that
individuals who have no need of soy, and even some to which soy could be hazardous, have started using it. Science is now
beginning to see what this "benign" protein can do, though.
This review will cover the negative effects that soy protein may have on fetal development of both males and females,
hormonal balance in males of a pre-mature and mature age, and efforts of weight training individuals trying to increase fat-free
muscle mass. Studies will be included of human and non-human species, both immature and mature in age. Only abstracts and
full-length articles from peer reviewed journals will be referenced in this paper.
Literature
Both abstracts and journals were found through the PubMed database and in the local university library. Limits were set
on searches such as "human only," "male," "female," "abstract only," and others. Key words used included "soy," "soy protein,"
"genistein," as well as "Testosterone production," "effects on Testosterone," and others. Finally, studies or points in favor
of soy were not included, as countless papers have been written on its positive effects.
Findings
The largest concern scientists have about soy are its effects on sexual development of infants consuming soy-based formula.
The data is startling, yet most concerns have fallen on deaf ears.
One study showed that when manufacturer-suggested amounts of soy formula are fed to infants, the infants ingest a daily
dose of approximately 3 mg of total isoflavones (i.e. genistein and daidzein) per kg of body weight, which is maintained at
a fairly constant level between 0 and 4 months of age.(3) Supplementing the diet of 4-month old infants with a single daily
serving of soy-based cereal can increase their isoflavone intake by over 25%, depending on the brand chosen.
This rate of isoflavone intake is much greater than that shown to alter reproductive hormones in adult humans. The available
evidence suggests that infants can digest and absorb dietary phytoestrogens in active forms and neonates are generally more
susceptible than adults to perturbations of the sex-steroid milieu.
Another study assessed the effect of administering neonatal animals genistein in the amount of 4 mg per kg per day from
days 2-18 of life.(1) Administration of genistein significantly retarded most measures of pubertal spermatogenesis. Plasma
FSH levels in the treatment groups changed in parallel to the spermatogenic changes (reduced when pubertal spermatogenesis
retarded, increased when pubertal spermatoenesis advanced).
By day 25, the changes in FSH levels largely persisted. In adulthood, the animals that were fed a soy-free diet in infancy
and on, had significantly larger testes than controls fed a soy-containing diet. Of the animals that had neonatal treatment
with genistein, a minority did not mate or were infertile.
In concluding this article, the authors stated "the presence or absence of soy or genistein in the diet has significant
short-term (pubertal spermatogenesis) and long-term (body weight, testis size, FSH levels, and possibly mating) effects on
males."
The ugliness continues. The developing fetus is uniquely sensitive to perturbation with estrogenic chemicals. The carcinogenic
effect of prenatal exposure to diethylstilbestrol (DES) is the classic example. The carcinogenic potential of genistein, a
naturally occurring plant estrogen in soy, has been shown in mice treated neonatally. In a study reported in the journal,
Cancer Research, the incidence of uterine adenocarcinoma in 18-month-old mice was 35% for genistein and 31% for DES (diethylstilbestrol).(6)
This data suggests that genistein is carcinogenic if exposure occurs during critical periods of differentiation. The
author admonished: "Thus, the use of soy-based infant formulas in the absence of medical necessity and the marketing of soy
products designed to appeal to children should be closely examined."
Finally, as far as soy and its effects on infants, hypothyroidism has been shown in infants receiving soy formula.(2)
The next major concern is genistein's estrogenic and anti-androgenic effects on adult male animals and humans. This effect
was shown clearly in a study on adult male reproductive tracts.(8) In intact adult male mice, genistein (2.5 mg per kg of
body weight per day for only 9 days) reduced testicular and serum Testosterone concentrations and pituitary LH-content. These
results suggest that genistein — in doses comparble to those that would exist in a soy-based diet — induced typical
estrogenic effects.
A second study showed plasma Testosterone and androstenedione levels were significantly lower in the animals fed a phytoestrogen-rich
diet compared with animals fed a phytoestrogen-free diet.(9) These results indicated that consumption of dietary phytoestrogens
over a relatively short period can significantly alter plasma androgen hormone levels.
In a study of Japanese men, total and free Testosterone concentrations were inversely correlated with soy product intake.
(5)
The evidence continues. In rats that were fed a diet in which casein was replaced by soy protein isolate/isoflavones,
both serum levels of Testosterone and weight of testes were significantly reduced.(7)
Finally, in a study that may correlate more strongly with weight-training athletes, diets that consist of inferior protein
(soy) may increase protein breakdown in skeletal muscle.(4) Pigs were fed diets based on soybean-protein isolate or casein
for 15 weeks. A transient rise in the level of cortisol was shown to occur in the postprandial phase only in the soybean group.
The authors of this study concluded: "These data suggest that the inferior quality of dietary soybean protein induces hormonally-mediated
upregulation of muscle protein breakdown for recruitment of circulatory amino acids in a postabsorptive state."
In other words, soy intake induces the body to break down muscle protein in order for it to get its required amino acids.
Conclusions
At this time it's recommended that:
• Infants not be given soy-based formula until more research is done on safety in regard to neonatal sexual development
and its effects on thyroid suppression.
• Men not use soy products until more research is done on its effects on Testosterone and testicular function.
• Weight-training individuals who hope for increased muscle hypertrophy not use soy protein until more research
is done on effects of decreased Testosterone, increased cortisol levels and muscle protein breakdown.
Scientists Protest Soy Approval in Unusual Letter
Scientists' Letter
DEPARTMENT OF HEALTH and HUMAN SERVICES Public Health Service Food and Drug Administration National Center For Toxicological
Research Jefferson, Ark. 72079-9502 Daniel M. Sheehan, Ph.D. Director, Estrogen Base Program Division of Genetic and Reproductive
Toxicology and Daniel 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,b).
Faber and Hughes (1993) showed alterations in LH regulation following this 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 (Harrison, 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 (Harrison, 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 the 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 Daniels 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. Linda 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 nearly complete now. As preliminary data, which is still confidential, may
be relevant to your decision, I suggest you contact Dr. Barry Delclos at the address on the letterhead, or email him.
Sincerely,
Daniel M. Sheehan
Daniel R. Doerge
References
1. Atanassova N (2000). Comparative Effects of Neonatal Exposure of Male Rats to Potent and Weak (Environmental) Estrogens
on Spermatogenesis at Puberty and the Relationship to Adult Testis Size and Fertility: Evidence for Stimulatory Effects of
Low Estrogen Levels. Endocrinology Vol. 141, No. 10 3898-3907
2. Chorazy PA (1995). Persistent hypothyroidism in an infant receiving a soy formula: case report and review of the literature.
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The Food Revolution
The Food Revolution reveals the truth about popular diets, genetically modified foods, ... "soy
is more insidious than hemlock." Fallon and Enig say the soy industry knows soy is ...
http://www.foodrevolution.org/what_about_soy.htmNG BBS — The Gay Soy Conspiracy.
its a load of crap i've drunk soy a milk my whole life and i've been able to
... The Soy Plants have Phyto Estrogens which is a natural estrogen not like the ...
http://www.newgrounds.com/bbs/topic/624588GMO and Latin American Soy Producers | Conspiracy Blogger ...
Soy beans were first domesticated and used for food
between the eleventh and ... More: GMO and Latin American Soy Poducers | Conspiracy Blogger Share and ...
http://www.conspiracyblogger.com/?p=264the soy conspiracy - pencil - pen vs. sword - output - track7
In the place that the other guys were, it had recently
been decided that Jay should go to the conspiracy and get himself hired as a "soy distribution engineer. ...
http://www.track7.org/output/pen/pencil/soystory.phpConspiracy Bloger
Research into unexplained phenomenon ... Bruce on GMO and Latin American Soy Producers. Toby Simpson
on Sarah Palin Resigns. mutuellle on Conspiracy Friday: Internet 2 Part 2 ...
http://www.conspiracyblogger.com/Soy
Junk food conspiracy "I think people ought to avoid soy products as if they were poison. ... The Dark Side of
Soy - There are over 100 years of studies showing that soy ...
http://www.whale.to/a/soy.htmlCanola Oil - How Toxic Is It?
Canola oil comes from the rape seed, which is part of the mustard family of plants.
Rape ... College said that children who got soy formula were more likely to develop thyroid ...
http://www.shirleys-wellness-cafe.com/canola.htm
