Day 035 - 12 Oct 94 - Page 39


     
     1        "The occurrence of both breast and colon cancer is
     2        strongly associated with modern affluence, suggesting that
     3        they may share important aetiological factors.  Indirect
     4        evidence, largely based on differences in cancer rates
     5        between countries and changes in rates amongst migrants,
     6        has implicated diet as potentially important, but specific
     7        aspects of diet have not yet been definitively identified
     8        from epidemiological investigations.  Much of the
     9        available information is derived from case-control studies
    10        in which reports from cancer patients about their past
    11        dietary practices are compared with those of persons
    12        without cancer. The possibility of biased reporting of
    13        former diets in these studies is difficult to eliminate.
    14        Prospective cohort studies, in which dietary variables
    15        measured among a large number of people are related to
    16        subsequent risks of cancer, should provide more dependable
    17        data, but these are only beginning to be available because
    18        it takes time to accumulate enough cancer cases.  The
    19        existing limited data suggest that, despite gross
    20        similarities i n the epidemiology of breast and colon
    21        cancer, incidence of the colon cancer is likely to be more
    22        responsive to dietary change and thus be easier to
    23        prevent".
    24
    25        I am not sure whether I am right or not, but does that not
    26        reflect what I just put to you a moment ago, that
    27        Dr. Willett's view in relation to diet and cancer is
    28        stronger in the field of colon cancer than it is in
    29        relation to breast cancer?
    30        A.  Allow me a moment to just re-read that sentence, if
    31        I may?
    32
    33   Q.   Yes.
    34        A.  Yes, he does seem to be saying here that dietary
    35        changes are more likely to affect the incidence of colon
    36        cancer than breast cancer, and I did not understand that
    37        to be precisely what you had asked me earlier.
    38
    39   Q.   It was not precisely, but surely this is right, is it not,
    40        Dr. Barnard, that if diet has a role in the aetiology of
    41        cancer, then the incidence of cancer is likely to be
    42        responsive to changes in the diet, is it not?
    43        A.  There is a very important distinction between
    44        responsiveness to treatment and whether or not an
    45        aetiologic agent is identified -----
    46
    47   Q.   Sorry, let me interrupt, not treatment -- prevention is
    48        what I am talking about?
    49        A.  OK, or prevention, for that matter.  For example, if a
    50        very small increase in dietary fat -- just to take an 
    51        hypothetical example -- were to increase the risk of 
    52        breast cancer substantially, say, an increase from 10 per 
    53        cent of calories to 20 per cent of calories, if that were
    54        to increase the risk of breast cancer, and if we were to
    55        assume for the moment that that was a causal link, that is
    56        not the same thing as saying that, perhaps, with colon
    57        cancer there are changes along much higher levels.  For
    58        example -- perhaps I am not saying this as clearly as
    59        I might.
    60

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