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...
> FINDINGS MAY SUPPORT SOY-DEMENTIA CORRELATION IN MALES
> (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.  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,  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.  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.  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. 
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.  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
> 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."  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  and high consumption of soy in Okinawa,
> Japan.  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,  appear to provide compelling evidence of a
> possible causal mechanism that might explain the soy-dementia
> correlation reported by White et al.  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?
>  White et al: "In this population, higher midlife tofu consumption
> was independently associated with indicators of cognitive impairment
> and brain atrophy in late life."
>  Goddard (scroll to): "Is There Reason to Believe Tofu May Cause
> Brain Atrophy?" http://iangoddard.net/soy.htm
>  Exp Neurol (Sep 2002): "Neurotrophic factors have long been known
> to promote neuronal survival and differentiation."
>  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 [...]."
>  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."
>  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."
>  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."
>  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."
>  Neurosci Lett (Feb 1999): "soy phytoestrogens significantly
> increased the mRNA levels of BDNF [...in] female rats."
>  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."
>  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."
>  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. "
>  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."
>  Dementia: http://okinawaprogram.com/images/dem.gif
>  Soy intake: http://okinawaprogram.com/images/ment.gif
> Some alternative views on soy:
> "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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