sur le colon
High protein diet is not associated to increased fecal water genotoxicity
K. Windey
Ann Nutr Metab 2011;58(suppl 3):4
Introduction: Colonic fermentation of proteins leads to the production
of short chain fatty acids. branched chain fatty acids. phenols.
sulphides and amines. Some of these metabolites are potentially toxic.
Objectives: We modified the degree of protein fermentation by
changing protein intake and investigated the impact on fecal water
genotoxicity.
Method/Design: After a 1-week run-in period with normal protein
(NP) intake. 20 healthy volunteers followed an isocaloric high
protein (HP) and low protein (LP) diet for 2 weeks in a randomized
cross-over study. Fibre and fat intake were kept constant. During the
run-in period and the second week of each intervention period the
volunteers completed a dietary journal and collected urine for 48h
and feces for 72h. Colonic protein fermentation was estimated from
the urinary concentration of p-cresol. Profiles of volatile organic
compounds (VOC) were analysed in fecal samples using GC-MS.
Metabolite profiles were compared using cluster analysis. Fecal water
genotoxicity was determined using the Comet assay and expressed as
tail length (TL). Genotoxicity was related to the metabolite profiles.
Results: Protein intake accounted for 26.6 ± 4.2% of energy
intake during the HP diet. 15.2 ± 2.2% during the NP and 12.0 ±
1.8% during the LP diet. Urinary p-cresol excretion was significantly
correlated with protein intake (r=0.314; p=0.015). Fecal water genotoxicity
was not different after the NP. HP or LP diet (p>0.05). Cluster
analysis of metabolite patterns according to genotoxicity revealed a
separation between the high toxicity (TL > 150) samples and the low
toxicity (TL < 100) samples. This separation was mainly due to the
presence of sufides in the high toxicity samples.
Conclusions: Higher protein intake is associated with a higher
degree of protein fermentation but not with a higher fecal water genotoxicity.
Increased genotoxicity was due to the presence of sulphides.
