Food Lipids: Chemistry, Nutrition, and Biotechnology

going that there is no consensus with regard to the effects of dietary fat on colon
cancer risk.
Is it fat or the calories it provides that affects cancer risk? In 1927 Hoffman
[120] suggested that the increase in cancer incidence seen then was due to overnutrition.
About 50 years later, Berg [121] made a similar suggestion, namely, that
increasing risk of hormone-related tumors was due to increased caloric intake.
Moreschi [122] showed in 1909 that transplanted tumors did not grow as well in
underfed mice as in freely fed ones. A few years later Rous [123] demonstrated that
neither spontaneous nor transplanted tumors showed optimal growth in rodents
whose food intake was restricted. Lavik and Baumann [124] studied dietary effects
on chemically induced skin tumors in mice. When the diet was low in both calories
and fat, tumor incidence was nil. Tumor incidence in mice fed diets low in fat but
high in calories was 48% higher than in those whose diet was low in calories but
high in fat and only 18% lower than that in mice fed a high-fat, high-calorie diet
(Table 4). Our work [125–128] showed that caloric restriction by 40% led to significantly
reduced incidence of chemically induced breast or colon tumors in rats
even when the restricted diet contained twice as much fat. At 10% caloric restriction
incidence of induced breast tumors in rats was unchanged, but tumors per tumor
bearing rat were reduced by 36% and total weight of tumors by 47%. Rats fed a
diet containing 26.7% corn oil but restricted by 25% exhibited lower tumor incidence,
fewer tumors, and smaller tumors than rats freely fed a diet containing only
5% fat (Table 5). In humans both colon [129,130] and gastric [131] cancer have
been correlated positively with caloric intake. Overweight in humans is clearly correlated
with increasing cancer risk [132–134].
The effects of fat in cancer need to be stratified by fat type, fat quantity, and total
caloric intake. There is too frequently a rush to judgment concerning effects of
specific nutrients. Much of the recent interest in diet and cancer can be traced to the
major paper by Doll and Peto [135] in which they suggested that as many as 35%
of deaths due to cancer might be associated with diet. They then made the following
comment: ‘‘It must be emphasized that the figure chosen (of 35% of cancers related
to diet) is highly speculative and chiefly refers to dietary factors which are not yet
reliably identified.’’ They also stated that ‘‘there is no evidence of any generalized
increase (in deaths due to cancer) other than that due to tobacco.’’
Table 4 Effects of Calories and Fat on Incidence
of Methylcholanthrene-Induced Skin Tumors
in Mice
Level of
Calories Fat
Tumor incidence
(%)
Low Low 0
High Low 54
Low High 28
High High 66
Source: From Ref. 124.
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.