Changes in Intestinal Condition, Fecal Microflora and Composition of Rectal Gas after Administration of Fructooligosaccharide and Lactulose at Different Doses

Abstract

Gut symptoms, faecal microflora and rectal gas composition were recorded and compared after the administration of fructo-oligosaccharide (FOS) and lactulose to a lactose-intolerant subject. The subject experienced no abnormal gut symptoms while receiving a low dose (3.1-6.2 g/day) of FOS. When he stopped taking FOS, his stool developed a foul odour within 1 week, and he experienced stiffness in his neck and shoulders. Administration of high doses (18.6-24.8 g/day) of FOS was associated with frequent flatus and bloat in the ascending and transverse colon. No bloat occurred when the subject was receiving lactulose (18.9-25.2 g/day), but frequent defaecation, rectal gas and a loose stool did become a problem. Bifidobacteria numbers recorded in stool samples increased from 109.1 to 1010.8 (from 2.9 to 66.2% of faecal flora) after administration of high doses of FOS and from 108.7 to 1010.5 (from 0.5 to 25.2% of faecal flora) after lactulose administration. The composition of rectal gas varied even between successive samples, and no clear relationship was established between the dose and composition of gas. The processes involved in bloat occurrence are discussed in the light of these results. It is concluded that, while administration of oligosaccharides such as FOS can be of great benefit to individuals such as the subject of this study who have low levels of Bifidobacterium spp. and related symptoms, the level of FOS doses should be chosen carefully so as to avoid undesirable effects such as bloat.