Abstract
Faecal concentrations of short chain fatty acids (SCFAs) and faecal water content were determined in 93 healthy volunteers. We found positive correlation between faecal water content and the concentration of acetic, propionic and butyric acid. Multiple correlations between different SCFAs were found and grouping of the correlations according to an assumed substrate specificity was observed. Acetic, propionic and n-butyric acid, that are derived from carbohydrates, were best related to each other, whereas the minor acids, derived mostly from proteins, formed another group. Some specific features of the branched chain fatty acids (iso-acids) were discovered: their faecal concentrations were very strongly correlated to each other (Rho=0.977), they did not correlate with the total concentration of SCFAs, and showed negative correlations to the faecal water content. These findings suggest that the iso-acids have common and specific substrates in vivo, possibly of endogenous origin.