Effect of Synthesized Inulin on Bowel Habit and Fecal Microflora in Healthy Adults with Low Fecal Frequency

Background Recently we developed a biosynthetic inulin (s-inulin) with a narrower range of degrees of polymerization and higher water solubility than existing natural inulins. This study was designed to determine the effect of s-inulin on bowel habit and fecal microflora and to examine the s-inulin safety in healthy male and female adults with low fecal frequency. Methods A randomized, double-blind, placebo-controlled, cross-over study was conducted, in which 12 g of s-inulin or placebo was given to 31 subjects daily for 2 weeks, and a 4-week wash-out period was interconnected before the intervention was crossed. The bowel habit parameters and the predominant genera of colonic bacteria were measured. Results Twenty-seven subjects were evaluable for efficacy and 31 evaluable for safety. There were significant improvement in all of the following three bowel habit parameters: ( i ) the number of stools per 2 weeks ; ( ii ) defecation-occurring days per 2 weeks ; and (iii) mean fecal volume (cc/day) (p < 0.05 each), during the s-inulin period compared with the placebo period. No significant difference was found in fecal counts of bifidobacteria and other bacteria among the run-in period (baseline), s-inulin period and placebo period, probably due to the sufficiently high fecal level of bifidobacteria at baseline. Intake of s-inulin did not cause any untoward side effect. Conclusions In healthy adult subjects who had low fecal frequency and average fecal level of bifidobacteria, 12 g/day s-inulin was well tolerated and led to significant improvement of bowel habits with a minimum effect on fecal microflora.