Effect of fatty acid chain length and saturation on the gastrointestinal handling and metabolic disposal of dietary fatty acids in women

The gastrointestinal handling and metabolic disposal of [1-C-13]palmitic ac id, [1-C-13] stearic acid and [1-C-13]oleic acid administered within a lipi d-casein-glucose-sucrose emulsion were examined in normal healthy women by determining both the amount and nature of the C-13 label in stool and label excreted on breath as (CO2)-C-13. The greatest excretion of C-13 label in stool was in the stearic acid trial (9.2 % of administered dose) whilst com paratively little label was observed in stool in either the palmitic acid ( 1.2 % of administered dose) or oleic acid (1.9 % of administered dose) tria ls. In both the palmitic acid and oleic acid trials, all of the label in st ool was identified as being present in the form in which it was administere d (i.e. [C-13]palmitic acid in the palmitic acid trial and [C-13]oleic acid in the oleic acid trial). In contrast, only 87 % of the label in the stool in the stearic acid trial was identified as [C-13]stearic acid, the remain der was identified as [C-13]palmitic acid which may reflect chain shortenin g of [1-C-13]stearic acid within the gastrointestinal tract. Small, but sta tistically significant, differences were observed in the time course of rec overy of C-13 label on breath over the initial 9 h of the study period (ole ic acid = palmitic acid > stearic acid). However, when calculated over the 24 h study period, the recovery of the label as (CO2)-C-13 was similar in a ll three trials (approximately 25 % of absorbed dose). These results suppor t the view that chain length and degree of unsaturation may influence the g astrointestinal handling and immediate metabolic disposal of these fatty ac ids even when presented within an emulsion.