Day 036 - 13 Oct 94 - Page 35
1 models. In the past few years our laboratory has been
2 studying the impact of several confounding factors that
3 could modulate the enhancing effect of fact on neoplastic
4 development of the mammary gland in female rats which are
5 treated with a carcinogen. It is our conclusion that fat
6 promotes carcinogenesis only under a very stringent set of
7 conditions which might not be duplicated in the arena of
8 fat intake and human breast cancer. Previous studies on
9 fat and mammary cancer in experimental models have used
10 young virgin rats which are given a dose of carcinogen at
11 a particular age. The question arises as to whether the
12 promoting effect of fat might be a consequence of the
13 characteristics of the model. We have supportive evidence
14 showing that the following criteria must be satisfied in
15 order for fat enhancement of mammary carcinogens to be
16 manifested: (a) carcinogen administered at a time when the
17 mammary gland is exquisitely susceptible to tumour
18 induction, (b) animals maintained on a semipurified diet,
19 (c) ad libitum feeding necessary, and (d) unusually high
20 requirement of linoleic acid for tumour development. On
21 the other hand, the stimulatory effect of fat is
22 attenuated or sometimes even negated by (a) feeding of a
23 natural ingredient diet, (b) submaximal calorie intake and
24 (c) previous history of pregnancy and lactation. Given
25 the spectrum of confounders that are inherent in
26 epidemiological studies linking fat intake and breast
27 cancer, including differences in lifestyle, reproductive
28 history, eating habits, as well as the complexity of the
29 total diet, our findings suggest there may be a need to
30 reevaluate the validity of extrapolating animal data that
31 are obtained under a highly defined set of conditions to
32 the aetiological significance of dietary fat in human
33 breast cancer." Academic Press Inc. 1993.
34
35 Please then turn, Dr. Barnard, to page 730. At the bottom
36 of page one find this: "Complexity of Diet Composition -
37 Conventional studies investigating the stimulatory effect
38 of fat on carcinogenesis have used a purified diet which
39 normally contains casein as the protein source together
40 with a complement of simple and complex sugars. The
41 addition of standard vitamin and mineral premixes
42 completes the formulation of a nutritionally balanced
43 diet. Experiments from the early work of Silverstone ...
44 clearly demonstrated that animals fed a crude diet were at
45 a lower risk of developing tumours than were those ped a
46 purified diet. We have similarly found that rats fed a
47 natural-ingredient diet (N1H-07 open formula diet) were
48 consistently less sensitive to DMBA-induced mammary
49 tumourgenesis compared with those fed a purified diet
50 (AIN-76 formulation) over a wide range of fat levels.
51 Even in the presence of a high-fat intake, rats on a
52 natural-ingredient diet developed only half as many
53 tumours as those on a purified diet. The attenuation of
54 the fat effect by the natural-ingredient diet was
55 reproducibly observed regardless of the protein level in
56 the diet or the method of feeding, i.e. ad libitum feeding
57 versus meal feeding. The NIH-07 open-formula diet
58 consists primarily of soybean meal, alfalfa meal and
59 ground corn and wheat. A vast array of chemicals with
60 anticancer activity have been identified in food, with
