THE METABOLIC IMPORTANCE OF UNABSORBED DIETARY LIPIDS IN THE COLON

Digestion and absorption of lipids is a highly efficient process. From Western diets about 95% will be absorbed. This implies that together with lipids from endogenous sources 6-8 g of lipids will enter the col on daily. This input significantly increases during various lipid mala bsorption syndromes. It has long been assumed that the biological fate of unabsorbed lipids is physiologically not relevant. However, signif icant microbial lipid metabolism occurs. Circumstantial evidence is ar ising which supports a role of unabsorbed lipid metabolites in the dev elopment of colonic diseases. Lipid metabolites may act as detergents in the colon, leading to mucosal injury and reactive hyperproliferatio n, which in its turn could promote tumour development. Lipid metabolit es could also be transformed in biological active metabolites, which h ave a tumour promoting potency. More mechanistic information is needed on the colonic metabolic fate of lipids in order to develop strategie s for manipulating colonic flora in the prevention of lipid related co lonic diseases.