Day 036 - 13 Oct 94 - Page 32


     
     1        cancer, a positive association between amounts of fat and
     2        incidence of breast cancer?
     3        A.  Yes.  What Dr. Willett argues is that even at very
     4        high intakes of fat, such as was found in the nurses
     5        study, one should be still able to see a little bit more
     6        breast cancer among those women on astronomical amounts of
     7        fat versus those on only moderately astronomical amounts
     8        of fat.
     9
    10   Q.   How explain the contrasting findings of Dr. Willett's work
    11        in relation to colon cancer on the one hand and breast
    12        cancer on the other?
    13        A.  Well, there are a number of different points that we
    14        have gone over already.  One has to say that when a clear
    15        and significant relationship is found, if that is only
    16        found in, say, one in 20 studies, or thereabouts it may be
    17        perhaps by chance alone, but aside from that, that it does
    18        not mean something, if one has investigated in a
    19        population and not found an association, that certainly
    20        does not disprove it.  What seems quite likely (and as
    21        Dr. Campbell's data suggest) is that, indeed, what is
    22        probably most important is dietary intake earlier in life,
    23        although as the studies of Gregorio, Verreault and others
    24        have indicated, there never seems to be a time where fat
    25        has no effect.  But what is earlier in life may be
    26        important.  It may well be, as Dr. Willett suggests, that
    27        lower fat intakes are where the threshold effect lies.
    28        That has been the suggestion of Dr. Campbell.
    29
    30        I would take issue with what Dr. Willett says here, such
    31        as below 20 per cent of energy being what is relevant.
    32        That may be true.  Regretfully, Dr. Willett's data do not
    33        get even anywhere near that level.  My recollection, I
    34        have not re-read this in a while, is that his lowest
    35        quintile is 27 per cent average fat intake.  Again, it is
    36        a short-term study.  Eight years is longer than four, but
    37        it is rather short.  In carcinogenesis eight years is in
    38        fact the time, an average time, between the beginning of
    39        cancer and before it is even detected.  So any woman who
    40        was diagnosed as, say, having cancer eight years out,
    41        already had cancer at the beginning of the study.
    42
    43        So, we have a very narrow range.  We have a short-term
    44        study and, as we described yesterday, his interpretation
    45        is something to which he is entitled.  I think he is quite
    46        capable of doing a well-designed study.  But that
    47        interpretation is not one which is supported by other
    48        authorities, or certainly most other authorities, although
    49        some do agree with Dr. Willett, it is not a majority view.
    50 
    51   Q.   I am going to be quite blunt with you, Dr. Barnard.  You 
    52        have not succeeded in showing us (and I do not know of any 
    53        authority certainly in the last eight or 10 years that has
    54        felt able to assert, whether it be a public authority or a
    55        professional scientist, with any confidence) that these
    56        associations we have been discussing are, indeed, causal?
    57        A.  The associations have not been proved.
    58
    59   Q.   That is not what I put.
    60

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