INABILITY OF THE HUMAN FECAL MICROFLORA TO METABOLIZE THE NONABSORBABLE FAT SUBSTITUTE, OLESTRA

Olestra is a non-caloric fat substitute under review by the Food and D rug Administration. It consists of a mixture of octa-, hepta- and hexa esters of sucrose formed with long chain fatty acids. Previous studies showed olestra is not hydrolyzed by mammalian lipases and is not abso rbed. The objective of this study was to evaluate the potential for co lonic microflora to metabolize olestra after continued exposure. Neat and emulsified C-14-[fatty acid] olestra was incubated for 72 h in bot h minimal and organically-enriched anaerobic media inoculated with fec es from seven subjects who had consumed olestra (9 g per day) over a 3 -4 week period. C-14-sucrose and C-14-glucose served as positive contr ols. Production Of (CO2)-C-14, (CH4)-C-14, C-14-volatile fatty acids ( VFAs) and C-14-long chain fatty acids (LCFAs) was determined. In addit ion, the ester distribution and fatty acid composition of olestra were examined before and after incubation. Significant quantities of (CO2) -C-14 and C-14-VFAs were generated from the C-14-sugars, indicating th at the microflora were active under the incubation conditions, Further more, free oleic acid was extensively hydroxylated and hydrogenated. i n contrast, no degradation products (gas, VFAs, LCFAs) or changes in t he olestra resulting from bacterial activity were detected. These resu lts indicate that under anaerobic conditions the colonic microflora of the humans, consuming olestra, did not metabolize olestra.