A comparison of the effects of dietary cellulose and fermentable galacto-oligosaccharide, in a rat model of colorectal carcinogenesis: fermentable fibre confers greater protection than non-fermentable fibre in both high and low fat backgrounds
Mvw. Wijnands et al., A comparison of the effects of dietary cellulose and fermentable galacto-oligosaccharide, in a rat model of colorectal carcinogenesis: fermentable fibre confers greater protection than non-fermentable fibre in both high and low fat backgrounds, CARCINOGENE, 20(4), 1999, pp. 651-656
The objective of this experiment was to compare the effects of diets with e
ither a non-fermentable fibre source (cellulose) or a fermentable fibre sou
rce [galacto-oligosaccharide (GOS)], combined with different levels of diet
ary fat, on the development of colorectal cancer. Male Wistar rats were fed
AIN(76)-based diets with either a low or high level of cellulose, or a low
or high level of GOS, for 9 months. The fat content of the diets was low,
medium or high. All rats were treated with 1,2-dimethylhydrazine to induce
colorectal tumours, Generally, the tumour incidence increased with increasi
ng fat content in the diet. Despite marked faeces bulking, dietary cellulos
e either had no effect or an enhancing effect on the formation of colorecta
l tumours in general, although the development of carcinomas was decreased.
GOS appeared to be highly protective against the development of colorectal
tumours, as was demonstrated by an inhibitory effect on tumour incidence,
multiplicity and size, regardless of the fat content of the diet. Neither f
ibre source influenced the bromodeoxyuridine labelling index determined in
colon crypts or tumours. In animals fed high-GOS diets, the caecal content
was significantly increased in weight and significantly decreased in pH, It
was concluded that tumorigenesis was enhanced by increased fat content of
the diet, and that the diets containing fermentable GOS conferred a greater
protection against colorectal cancer than did the diets containing nonferm
entable cellulose.