Day 269 - 25 Jun 96 - Page 10
1 what Dr. Arnott said that epidemiological evidence requires
2 support from independent sources the best of which is
3 experiment which provide a rational mechanism?
4 A. Yes, I think so. I mean, there was a stage when there
5 was a very strong correlation between the sale of nylon
6 stockings and the rise in coronary heart disease in Denmark
7 after the last war, but you really require to have a
8 logical biological mechanism to explain the connection and
9 nobody came up with a biological mechanism to explain the
10 connection with the sale of nylon stockings. And, in fact,
11 the epidemiological evidence proved that it was wrong
12 because on follow-up it did not pan out. The sale of nylon
13 stockings leveled off and coronary heart disease still
14 continued to rise.
15
16 But I think most people in science would say we need a bit
17 more than an association between high risk; we need an
18 explanation for that, and the explanations come from the
19 experimental laboratory. I think what I am saying is that
20 there is a very heavy weight of evidence showing that in
21 virtually all experimental animal models saturated fats, a
22 high saturated fat diet will induce changes in the blood
23 vessels which, although not identical because there are
24 species differences, are enough to make people believe that
25 these are an explanation for what is happening in the
26 human.
27
28 There were studies, I believe it was Whistler, some time
29 ago done in primates where he used the actual canteen diets
30 that were rich in this kind of saturated fat diets that we
31 are talking about and compared them with prudent diets
32 which were being recommended by the American Heart
33 Association, and there was a very clear difference in the
34 genesis of atherosclerosis which was almost identical. You
35 could not really tell the difference in the primate with
36 the human atheroma in the primates fed the canteen diet as
37 opposed to those fed the prudent diet.
38
39 So I think you need that kind of supporting evidence, my
40 Lord, to translate what you see as a difference between two
41 populations and what you suspect from measuring the risk
42 factors in those populations to translate it into a
43 mechanism at the biological level.
44
45 MS. STEEL: Right. So you are looking for some kind of
46 plausible biological mechanism?
47 A. Yes, and I think we have that. You essentially have
48 to test your hypothesis in some way and it is exceedingly
49 difficult to test a hypothesis in a human population, for
50 obvious reasons, so you have resort to the experimental
51 laboratory.
52
53 Q. Right, okay.
54
55 "In the lower socio-economic groups one in three men will
56 have a heart attack or stroke before they reach the age of
57 retirement. To get an idea of the contribution to risk one
58 can use the factorial calculation of the proportions which
59 gives at 70% of risk a figure of 63,500 heart attacks and
60 31,750 at a minimum. If saturated fats and trans-isomers
