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Soy Neurotoxicity?

Ian Goddard iamgoddard at yahoo.com
Mon Aug 11 14:04:05 EST 2003

tcarter2 at elp.rr.com (Thomas Carter) wrote:

>      I first read the paper with a sense of doubt that the long
>standing custom of tofu consumption could display enough negative
>power to stand out against such a cacophony of variables. 

  IAN: Well, your conclusions certainly supported your bias.

>Table 1 first caught my eye because of the small size of the low tofu
>consumption group and the astounding fact that the authors had ignored
>the second dietary survey, basing the table on the results of only the
>first. In the absence of an explanation this surely smacks of
>"doctoring" data. 

  IAN: This is the Table 1 title: "Characteristics at Baseline and 
  at the Time of Cognitive Assessment, according to Response at 
  Baseline to the Question: 'How Often do You Eat Tofu?'" 

>At the very bottom of the table they give scores of
>the intelligence test. (CASI) It turns out that the failures of the
>low consumption group are only 2.0%. This is an impossible number
>since the denominator of the calculation is 38, the group size. If
>unadjusted it must clearly be zero, or some multiple of 2.6%,
>corresponding to failures of 1,2, 3 individuals etc. divided by 38.
>The paper says these values were adjusted for age, and education, (why
>only these factors among the many available?) but such an adjustment
>would leave the values at zero or raise them to some value higher than
>2.6%, probably, judging from similar adjustments in the study to about
>four or five, which would take away almost all of the impact of tofu
>consumption. "Mistakes" like this are almost always indicative of data
>doctoring IMO.

  IAN: It says, "CASI score adjusted for age (single year) and 
  years of schooling completed." As such, it need NOT be 2.6%.
  So you base the charge of "data doctoring" on your assumption 
  that the figure "probably" should have adjusted to some number 
  other than 2%. What a flimsy basis for such a harsh accusation!

>       The hypothesis of the authors is not that the tofu consumption
>in the cohort is associated with lifelong lower intelligence, but with
>"accelerated brain aging". Figure two clearly shows them wrong on both
>counts. The median age at testing was 80, putting the first two bar
>graphs below the medium, and the last three above. A quick glance

  IAN: Frankly, I don't believe your "quick glance" supercedes 
  the expertise of eight professional epidemeologists who spent
  years examining all the data. Frankly, that you believe you  
  can debunk these experts in a few moments speaks for itself.
  Moreover, that in a few moments you feel qualified to accuse
  these professionals of "data doctoring" because some numbers
  are "probably" not what you think they should be is outrageous.

>shows that the younger members of the hi-hi tofu group failed at about
>four times the rate of the low-low tofu group. As the members get
>older this failure rate is gradually reduced to near equality.
>Comparisons of the other two groups show the same trend but not as

  IAN: That's a cross-sectional, not longitudinal, analysis,
  so you can't really say, "As the members get older this 
  failure rate is gradually reduced," since each stratified
  group represents a different set of people. The important 
  point is the sixth grouping showing the overall relation:


>Why were the hi tofu eaters so much less
>intelligent at age 71-75 than the low group? They went to grade school
>in Japan. People always (groups, not individuals) demonstrate a
>relative lack of intelligence when dealing with written or oral tests
>in a second language. 

  IAN: But the study states: "The CASI has been validated as 
  a screening instrument for dementia in the United States 
  and Japan, in both English and Japanese languages. [...] 
  participants selected either Japanese or English for testing, 
  depending on the language with which they were most comfortable."

  So your conclusion that scores were biased by native education
  stands in direct opposition to information provided in the study.

>A most pertinent example of this is the wives of
>the cohort. Those who went to grade school in Japan failed the CASI
>test at a rate of 2.7 times those who didn't (table 4). 

  IAN: That's irrelevant due to your oversight noted above. 

>have eliminated the difference in the CASI scores of the husbands at
>age 71, and would have destroyed the thesis of the paper. 

  IAN: That's a false assumption based on your oversight above. 

  Frankly, I just don't have time to respond point-by-point. 
  Given that you're asking us to believe your personal analysis 
  and thereby doubt eight expert epidemiologists and their peer-
  reviewers, it's fair to ask: exactly what are your credentials?
  I don't care for appeals to authority, but regarding complex
  statistical data analyses, expertise really means something.

  One last comment:

>      Contrary to the CASI data the relationship with brain size was
>most pronounced in the hi-hi group, being totally insignificant
>between the other three groups. I would guess that this was caused by
>lower growth due to the fact that soy protein is lacking in
>methionine, a deficiency of which is known to slow growth rates, but
>only at hi levels of deficiency.  The high-high group, which show
>lowered growth would have been deficient to at least some extent in
>this amino acid, the restriction of which is also shown to extend

  IAN: So there IS a relation to smaller brain size and tofu 
  (which was the primary focus of my post), but alas you've 
  determined that it is a result of methionine deficiency. 
  http://www.jacn.org/cgi/content/full/19/2/242/F3  You know,
  you could broach your comments as hypotheses and questions,
  rather than, as you have, accusations of "data doctoring" and 
  firm conclusions of "fatal mistakes" and such by the authors
  that you use to caste sweeping aspersion on peer-review per se.
  Moreover, you should locate and ask the authors directly before
  posting public accusations against their expertise and honor. 


  "Our greatest illusion is to believe that we are what 
   we think ourselves to be." Henri Amiel (1821-1881)


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