Selective in vivo effect of chitosan on fatty acid, neutral sterol and bile acid excretion: a longitudinal study.

Chitosan, a deacetylated form of chitin, is a dietary fibre known for its hypolipidemic properties, which are mainly attributed to its unique cationic characteristics. We studied the selective in vivo effect of chitosan on fat excretion in order to elucidate its hypolipidemic mechanism. A 4-week longitudinal study was conducted in guinea pigs and the effect of chitosan on fat-absorption was compared to that of a soluble fibre: digestion-resistant maltodextrin. Animals were fed with high-fat isocaloric diets containing 12/100g of cellulose, digestion-resistant maltodextrin or chitosan. Subsequently, the excretion of fatty acids, neutral sterols and bile acids was determined. Chitosan selectively reduced fat absorption in comparison to digestion-resistant maltodextrin. The excretion of lauric, myristic and palmitic fatty acids of animals fed with chitosan was more than 10-, 5- and 2-fold higher, respectively, than in the cellulose group, whereas stearic acid excretion was not significantly altered. Oleic, linoleic and α-linolenic acid excretion were also significantly higher (P<0.001). The n-6/n-3 ratio in faeces of the chitosan group was 23.68, compared to 13.95 in the cellulose group. Total neutral sterol excretion was increased by both dietary fibres, whereas bile acid excretion was only increased by chitosan. Nevertheless, chitosan inhibited the intestinal bioconversion of cholesterol and primary bile acids to secondary metabolites. Hence, these results reveal that chitosan and digestion resistant maltodextrin exert their hypolipidemic activity by different mechanisms.