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Soy Neurotoxicity?

George W. Cherry GWCherryHatesGreenEggsAndSpam at alum.mit.edu
Sat Aug 9 13:57:44 EST 2003

"Ian Goddard" <igoddard at erols.mom> wrote in message
news:0v53jvsnc8c06r4jbe8030jfo6ostlegvg at 4ax.com...
> (c) 08/06/03 - Ian Williams Goddard
> In April 2000, Lon White and others reported a dose-dependent positive
> correlation between tofu consumption and brain atrophy in a large
> sample of men over several decades. [1] While correlation does not
> prove causation, study size and duration along with the robust
> dose-dependent relationship caused me, even as a vegetarian, to avoid
> tofu and other soy products.

This is a nagging question for me also. I'm a vegetarian
also, and I used to regard soy beans and products made
from soy beans as ideal legumes and products made
from legumes. (Soy beans have a large amount of iron,
protein, and fiber per calorie.) I have largely eliminated
tofu, but I still consume soy milk, tempeh, and soy beans.
Perhaps I should stop consuming these foods also. This
thread may help me make that decision.

> Correlation-based hypotheses should be tested against the availability
> of possible causal mechanisms. In addition to possible causal
> mechanisms previously cited by this author, [2] recent findings
> significantly increase the case for a causal mechanism of soy-induced
> brain atrophy.
> Pro-Atrophy Pharmacology Indicated
> Brain-derived neurotrophic factor (BDNF) facilitates the survival and
> genesis of brain cells. [3-4] The neuroprotective effects of caloric
> restriction are attributed in part to increased BDNF. [5] On the other
> hand, reduced BDNF is known to cause brain-cell atrophy and is
> associated with Alzheimer's disease. [6-7] Now, a study in
> "Neuroscience Letters" reports that soy significantly reduced BDNF in
> the hippocampus and cerebral cortex of male rats. [8] Since reduced
> BDNF can cause neural atrophy, these findings appear to provide
> compelling evidence for a causal mechanism that might explain the
> positive correlation between tofu (soy) consumption and brain atrophy
> demonstrated by White et al. [1]

Is it correct to equate tofu and other soy products (beans
and tempeh, for example)? What form of soy was used in
the rat study you cite?

> Bad For Boys, Good For Girls?

I think I recall that the wives of the men studied
in Hawaii also experienced dose-dependent cog-
nitive slippage. (That study used tofu).

> While soy appears to reduce BDNF in male rats, it has also been shown
> to increase BDNF in female rats. [9] In fact, soy appears to affect
> neurological parameters in a sex-defined fashion wherein females
> benefit and males suffer. [10-13] There is little doubt among
> researchers that this is because soy is high in phytoestrogens, which
> are plant-derived substances that act like the female hormone
> estrogen.
> However, that sex-defined difference fails to explain the findings
> regarding the wives of male subjects in White et al, who reported: "A
> similar association of midlife tofu intake with poor late life
> cognitive test scores was also observed among wives of cohort members,
> using the husband's answers to food frequency questions as proxy for
> the wife's consumption." [1] White et al proposed that long-term
> consumption of weaker soy estrogens may displace the body's own
> stronger estrogen along with its benefits.

Yes, this is what I referred to above.

> Evidence Against Soy-Dementia Hypothesis?
> A possible signal contrary to a soy-dementia link is the low
> prevalence of dementia [14] and high consumption of soy in Okinawa,
> Japan. [15] However, that negative correlation, like any correlation,
> does not prove causation. For example, perhaps soy does cause dementia
> but other factors in Okinawa offset the effect.
> Also, White et al explored correlations of a range of foods to
> neurological parameters, whereas this Okinawa analysis is a sweeping
> generalization of only tofu to all of Okinawa. In other words, it
> stands to reason that the study by White et al finding a positive
> tofu-dementia correlation has the greater likelihood of providing the
> more accurate picture. Nevertheless, in my view this Okinawa data
> warrants further examination as a possible route to falsifying the
> soy-dementia hypotheses.
> In closing, the findings of soy-induced BDNF reduction in male rat
> brain regions that are central to the onset of dementia, in addition
> to previous findings, [2] appear to provide compelling evidence of a
> possible causal mechanism that might explain the soy-dementia
> correlation reported by White et al. [1] Obviously further research is
> necessary before a clear picture emerges regarding the effects of
> long-term soy consumption on the brain. But in the meantime, my
> inclination is to play it safe and avoid soy.

Could it be (I have my fingers crossed) that the
problem lies in the tofu process rather than the bean?


> [1] White et al: "In this population, higher midlife tofu consumption
> was independently associated with indicators of cognitive impairment
> and brain atrophy in late life."
> [2] Goddard (scroll to): "Is There Reason to Believe Tofu May Cause
> Brain Atrophy?" http://iangoddard.net/soy.htm
> [3] Exp Neurol (Sep 2002): "Neurotrophic factors have long been known
> to promote neuronal survival and differentiation."
> http://www.neuro.mpg.de/research/csn/bdnf_ltp
> [4] J Neurochem (Sep 2002): "These findings suggest that BDNF plays an
> important role in the regulation of the basal level of neurogenesis in
> dentate gyrus of adult mice [...]."
> [5] Endocrinology (Jun 2003): "Recent studies have shown that DR
> [dietary restriction] stimulates the production of brain-derived
> neurotrophic factor (BDNF) in brain cells, which may mediate
> neuroprotective and neurogenic actions of DR."
> [6] Arch Gen Psychiatry (Jul 1997): "stress can decrease the
> expression of brain-derived neurotrophic factor and lead to atrophy of
> these same populations of stress-vulnerable hippocampal neurons."
> [7] Brain Res Mol Brain Res (Oct 3, 1997): "a reduction in BDNF mRNA
> expression has been observed in human post-mortem Alzheimer's disease
> hippocampi. [...] These results support and extend previous findings
> that BDNF mRNA is reduced in the human Alzheimer's disease hippocampus
> and temporal cortex, and suggest that loss of BDNF may contribute to
> the progressive atrophy of neurons in Alzheimer's disease."
> [8] Neurosci Lett (Feb 27, 2003): "significant reductions were found
> in brain-derived neurotrophic factor (BDNF) mRNA expression in the CA3
> and CA4 region of the hippocampus and in the cerebral cortex in the
> [male] rats fed the diet containing phytoestrogens, compared with
> those on the soya-free diet."
> [9] Neurosci Lett (Feb 1999): "soy phytoestrogens significantly
> increased the mRNA levels of BDNF [...in] female rats."
> [10] Neurotoxicol Teratol (Jan-Feb 2002): "when learning and memory
> parameters were examined in a radial arm maze testing visual-spatial
> memory (VSM), the diet treatments significantly changed the typical
> sexually dimorphic pattern of VSM. Specifically, adult Phyto-rich fed
> females outperformed Phyto-free fed females, while in males on the
> same diets, the opposite pattern of maze performance was observed."
> [11] BMC Neurosci (2001 2(1):20): "Female rats receiving lifelong
> exposure to a high-phytoestrogen containing diet (Phyto-600) acquired
> the maze faster than females fed a phytoestrogen-free diet
> (Phyto-free); in males the opposite diet effect was identified. [...]
> These findings suggest that dietary soy derived phytoestrogens can
> influence learning and memory and alter the expression of proteins
> involved in neural protection and inflammation in rats."
> [12] BMC Neurosis (2001 2(1):21): "When a diet change was initiated in
> adulthood, control phytoestrogen-rich fed females outperformed control
> females switched to a phytoestrogen-free diet. Whereas, in control
> males the opposite diet effect was identified. "
> [13] Neurosci Lett (May 15, 2003): "This study is the first to show
> that lifelong consumption of dietary phytoestrogens alters the HPA
> stress response in male rats."
> [14] Dementia: http://okinawaprogram.com/images/dem.gif
> [15] Soy intake: http://okinawaprogram.com/images/ment.gif
> Some alternative views on soy:
> http://www.soyonlineservice.co.nz
> http://www.healingcrow.com/soy/soy.html
>  http://IanGoddard.net/journal.htm
>  "To lengthen thy life, lessen thy meals." Ben Franklin
>  Ongoing CR-monkey-study update: "In the monkeys...those on
>  reduced feeding since the study started are dying at a rate
>  that is about half that of the monkeys receiving a full food
>  ration." Associated Press: Eating less may extend human life.
>  August 1, 2002 : http://www.msnbc.com/news/788746.asp?0si=-

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