Inulin measured as fructose in faeces of rats fed sucrose-based diets is not confounded by the presence of fructose derived from sucrose

Publication date: Available online 5 April 2017
Source:Bioactive Carbohydrates and Dietary Fibre
Author(s): John A Monro, Gunaranjan Paturi
This study aimed to determine whether measurements of faecal inulin as fructose in the faeces of rats fed inulin in sucrose-based diets are confounded by fructose derived from sucrose. Sprague-Dawley rats were fed diets containing 58.5% sucrose supplemented with 5% cellulose (control) or 5% inulin for 7 or 14 days. Fructose or fructose polymer in the faeces was extracted with hot 0.1M hydrochloric acid and measured with a specific colourimetric method. Nearly all (99.8%) of the fructose fed as sucrose in cellulose-supplemented diets did not appear in the faeces. In rats fed 5% inulin, about 98.5% of the total dietary fructose was utilised, and approximately 1.5% appeared in faeces. By subtracting apparent sucrose-derived fructose in the cellulose control diets from total fructose in the faeces from inulin-fed animals, faecal fructose was calculated to be about 10% of the inulin that had been consumed. A small proportion of inulin fed to rats at a level of 5% in the diet may survive caecal fermentation and appear in the faeces. This faecal inulin may be measured without interference from sucrose-derived fructose when fed in starch-free diets using sucrose as the sole source of digestible carbohydrate.



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