Dietary fat and colon cancer: Animal model studies |
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Authors: | Bandaru S Reddy |
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Affiliation: | (1) Div. of Nutritional Carcinogenesis, American Health Foundation, 1 Dana Rd., 10595 Valhalla, NY |
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Abstract: | Since it was first suggested that high dietary fat is a risk factor in colon cancer, there have been several studies to test
this hypothesis. Epidemiologic studies suggested a positive association between dietary fat and colon cancer. Laboratory animal
model studies demonstrated that not only the amount of rat, but also types of fat differing in fatty acid composition are
important determining factors in colon tumor development. Chemically-induced colon tumor incidence was increased in rats fed
the semipurified diets containing 23% corn oil, safflower oil, lard or beef tallow (high-fat) as compared to those fed 5%
corn oil, safflower oil, lard or beef tallow diets (low-fat). Diets containing 23% conconut oil, olive oil or fish oil, or
high-fat diets containing varying levels oftrans fat, had no colon tumor-enhancing effect compared to their respective low fat diets. The stage at which the effect of dietary
fat is exerted appears to be mostly during the post-initiation phase of colon carcinogenesis. Lack of a colon tumor enhancing
effect of dietary fish oil is observed both during the initiation and postinitiation phases. The mechanisms by which various
dietary fats increase colon carcinogenesis are not fully understood. In most instances, however, the high-fat diet appears
to enhance tumorigenesis through elevation of agents, such as secondary bile acids, that act as promoters of tumor development.
Lack of colon tumor promotion by dietary fish oil andtrans fat appears to be mediated through their effect on mucosal ornithine decarboxylase activity, colonic secondary bile acids
and/or prostaglandin synthesis.
Based on a paper presented at the Symposium on Lipids in Cancer held at the AOCS Annual Meeting, Baltimore, MD, April 1990. |
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