Day 033 - 10 Oct 94 - Page 21
1 quite a different diet, have about half that prevalence of
2 latent prostate cancers.
3
4 If one then also observes statistics on the likelihood of
5 dying of prostate disease, the countries vary in precisely
6 the same way; the higher the intake of fat, the more
7 likely one is to -- the higher the rates of prostatic
8 cancer deaths.
9
10 Q. So on that second point, the promotive -- would that be a
11 promotive effect of fat in the diet?
12 A. Yes.
13
14 MR. JUSTICE BELL: So you have got initiation and promotion,
15 but you have not got progression?
16 A. Right. The same factors that promote the growth of
17 cancer cells will, presumably, also encourage progression,
18 so that one will see metastasis to distant sites as well
19 as invasion of adjacent areas to the tumour.
20
21 MR. MORRIS: Moving on to colon cancer, would you like to
22 summarise the dietary implications of colon cancer?
23 A. Yes. Here, both fat and fibre seem to play a role.
24 Dr. Denis Burkitt (who I mentioned earlier) published
25 observations based on his work in Africa where he was a
26 missionary surgeon and became quite famous as a cancer
27 researcher for identifying Burkitt's, what came to be
28 known as Burkitt's lymphoma.
29
30 Following on the heels of that work, he became interested
31 in why are certain cancers quite common in the United
32 Kingdom and in other westernised countries, and why are
33 they uncommon in Africa? He published a review of
34 epidemiological evidence in 1971, giving particular
35 emphasis to the role of fibre; that a high fibre diet is
36 associated with lower rates of colon cancer. Also he
37 hypothesised mechanisms by which that might operate; that
38 carcinogens that may be in the digestive tract can be
39 deluded by a high fibre intake.
40
41 A high fibre intake makes the stools considerably more
42 bulky and the fibre absorbs water rather like a sponge
43 soaks up water; the carcinogens are absorbed and deluded
44 in the process. That reduces the concentration of
45 carcinogens on the wall of the large bowel. This is the
46 presumed mechanism, or one of the mechanisms. However,
47 since that time other mechanisms have been suggested and
48 studied which I describe in my statement here.
49
50 The international comparisons parallel those with breast
51 cancer and prostate cancer in that countries that have a
52 higher fat intake have a higher rate of colon cancer in
53 general terms. Likewise, countries that have a higher
54 fibre intake have a lower rate of colon cancer.
55 Case-control studies in which individuals who have cancer
56 are then compared to individuals who are like them in
57 other ways but do not have cancer, and in case-control
58 studies, a study was done in Canada, for example, that
59 showed an association between, on the one hand, fat,
60 saturated fat, and total calories and cancer of the
