Day 034 - 11 Oct 94 - Page 11


     
     1        positive association is right, a sceptic about association
     2        of fat just cannot win, can he, because wherever there is
     3        no association you say that does not help at all, and
     4        wherever there is association you say:  "Look, that
     5        supports what I am saying"?
     6        A.  A sceptic, I think, could win if the great bulk of
     7        studies showed no association whatsoever.  If the animal
     8        studies showed no association and if there were no
     9        plausible biological mechanisms that had been established,
    10        then I would say the sceptics had the weight of evidence
    11        on their side.
    12
    13   Q.   But only, in your mind, if that were so?
    14        A.  Yes.
    15
    16   MR. MORRIS:  If, presumably, it is a question of the positive
    17        associations that have been found were somehow by chance,
    18        presumably, there would be as many studies that maybe
    19        showed a negative association, if there was really no
    20        association?
    21        A.  It is impossible to have this many positive findings
    22        by chance.  It is possible to have one in 20 studies could
    23        be found by chance to be positive or to be negative.  The
    24        reason I use the No. 1 in 20 is that when statistical
    25        significance is reported, for example, any one of these
    26        positive marks, the first one Lea 1966, to report a
    27        positive association between total fat and breast cancer
    28        and to report that is statistically significant; what they
    29        mean is they have analysed the data, they have done
    30        statistical tests on them to show that 19 times out of 20,
    31        or 95 per cent of the time, that could not have occurred
    32        by chance alone; but that one time in 20 it is just
    33        possible that that could have happened by chance; that
    34        just that many more people happened by pure chance to be
    35        consuming lots of fat and to end up with cancer; but in 19
    36        out of 20 cases that would not occur by chance alone.
    37
    38        The reason I mention that is that if you do enough studies
    39        you will find some that by chance alone are positive or
    40        are negative.  As we have seen, there are a couple of
    41        negatives on this chart.  The more studies one does the
    42        more of those there might be, even if, in fact, that is
    43        simply a fluke.  One would expect about one in 20 studies
    44        to show nothing other than a chance relationship.
    45
    46   MR. MORRIS:  Those two -- well, yes, okay.
    47        A.  I am not saying that was the case in those studies.
    48        I am saying that about one in 20 studies you can write off
    49        to pure chance.  However, it is impossible to write off
    50        all of these studies.  This is overwhelming, very 
    51        convincing evidence of a relationship. 
    52 
    53   MR. JUSTICE BELL:  What I would like to do, Mr. Morris, unless
    54        it is inconvenient to you, if you go through the cohort
    55        studies and ask whatever questions you want to ask
    56        Dr. Barnard of that; then you have been through the whole
    57        table.  Then, might I suggest, that you ask Dr. Barnard if
    58        this were an accurate bird's eye view, what it meant to
    59        him.  He may have already expressed his view in the last
    60        answer, I do not know.  Then I can compare it with the

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