Day 022 - 12 Sep 94 - Page 07
1 A. It depends which cancer you are talking about. As far
2 as breast cancer is concerned, I think that we do not know
3 the answer to this. But certainly it does appear that
4 those women who develop breast cancer and are obese have a
5 worst outlook. We have discussed this point already. As
6 far as colorectal cancer is concerned, again the evidence
7 is conflicting because you can find one study that, for
8 example, shows an association with, say, fat intake and
9 the development of colorectal cancer, and then you will
10 find another study which, well conducted, does not show
11 any association. There is no consistency in the finding.
12
13 But, perhaps, the dietary factor which does have the
14 strongest association is that fruits and vegetables,
15 grains, probably exert a protective effect. But again
16 that is by no means absolute because again some studies
17 have not shown this effect. This is the problem that you
18 can -- the evidence is controversial.
19
20 Q. But it is also true to say that you have not shown cause
21 and effect for some of the other factors you mentioned?
22 A. All of these studies are epidemiological;
23 epidemiological studies are observational. It is,
24 therefore, very difficult, unless the evidence is
25 absolutely cast iron or very strong indeed, to show cause
26 and effect -- for example, the strongest epidemiological
27 study looked at cigarette smoking in the development of
28 lung cancer. There was such a consistency of finding
29 there that one could say that cigarettes were involved in
30 the causation of lung cancer, but that did not necessarily
31 show you what actually caused the lung cancer, what it was
32 in cigarettes that caused lung cancer; it took some
33 further research to suggest it might be the tars.
34
35 Q. We have not got to the position where we can say for
36 certain that you can show cause and effect in relation to
37 smoking and lung cancer?
38 A. It is likely to be the tars in the cigarettes, but
39 that is the closest one can say.
40
41 Q. We do not know for definite?
42 A. We do not absolutely know.
43
44 Q. Would you agree that there is a large body of medical
45 scientific opinion that does think there are dietary
46 factors involved in these cancers?
47 A. There is certainly a body of evidence, of people who
48 feel that there is likely to be some dietary factor which
49 may be involved in the development of breast and colon
50 cancer, but I think what cannot be said is that we know
51 what that dietary factor is. You see, we have talked
52 about this already, that this migration of people -- it is
53 very easy, for example, to look at fat consumption because
54 it is easy to register, or relatively easy to register,
55 the amount of fat which is produced in a country or
56 apparently used in a country and incidence of, say, breast
57 or colorectal cancer.
58
59 But when you actually look at carefully controlled
60 studies, such as prospective studies which have looked at
