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 Drug Administration. It consists of a mixture of octa-, hepta- and hexaesters of sucrose formed with long chain fatty acids. Previous studies showed olestra is not hydrolyzed by mammalian lipases and is not absorbed. The objective of this study was to evaluate the potential for colonic microflora to metabolize olestra after continued exposure. Neat and emulsified14C-[fatty acid] olestra was incubated for 72 h in both minimal and organically-enriched anaerobic media inoculated with feces from seven subjects who had consumed olestra (9 g per day) over a 3–4 week period.14C-sucrose and14C-glucose served as positive controls. Production of14CO2,14CH4,14C-volatile fatty acids (VFAs) and14C-long chain fatty acids (LCFAs) was determined. In addition, the ester distribution and fatty acid composition of olestra were examined before and after incubation. Significant quantities of14CO2 and14C-VFAs were generated from the14C-sugars, indicating that the microflora were active under the incubation conditions. Furthermore, free oleic acid was extensively hydroxylated and hydrogenated. In contrast, no degradation products (gas, VFAs, LCFAs) or changes in the olestra resulting from bacterial activity were detected. These results indicate that under anaerobic conditions the colonic microflora of the humans, consuming olestra, did not metabolize olestra.
Key wordsGI microflora Bacterial catabolism Fat substitute Olestra
Unable to display preview. Download preview PDF.
- 1.Eyssen, H.J. and G.G. Parmentier. 1974. Influence of the microflora of the rat on the metabolism of fatty acids, sterols and bile salts in the intestinal tract. Zbl. Bakt. Suppl. 7: 39–44.Google Scholar
- 6.Manning, B.W., T.W. Federle and C.E. Cerniglia. 1987. Use of semicontinuous culture system as a model for determining the rule of human intestinal microflora in the metabolism of xenobiotics. J. Microbiol. Methods 6: 81–94.Google Scholar
- 10.McInerney, M.J., M.P. Bryant and N. Pfennig. 1979. Anaerobic bacteria that degrades fatty acids in synthrophic association with methanogens. Arch. Microbiol. 122: 129–135.Google Scholar
- 12.National Research Council. 1989. Diet and Health: Implications for Reducing Chronic Disease Risk. National Academy Press, Washington, DC.Google Scholar
- 15.Spain, J.C., P.H. Pritchard and A.W. Bourquin. 1980. Effects of adaptation on biodegradation rates in sediment/water cores from estuarine and freshwater environments. Appl. Environ. Microbiol. 40: 726–734.Google Scholar
- 17.Weng, C.N. and J.S. Jeris. 1976. Biochemical mechanisms in the methane fermentation of glutamic and oleic acids. Water Res. 10: 9–18.Google Scholar
- 18.Wrong O.M., C.J. Edmonds and V.S. Chadwick. 1981. The Large Intestine: Its Role in Mammalian Nutrition and Homeostasis. John Wiley and Sons, New York.Google Scholar