Short-chain fructo-oligosaccharide administration dose-dependently increases fecal bifidobacteria in healthy humans

Short-chain fructo-oligosaccharides (SC-FOS) are a mixture of oligosaccharides consisting of glucose linked to fructose units (Gf(n); n = ≤ 4), which are not digested in the human small intestine but are fermented in the colon where they specifically promote the growth of bifidobacteria. In healthy volunteers, we assessed the tolerance and the threshold dose of SC- FOS that significantly increased fecal bifidobacteria counts and the possibility of a dose-response relationship. Randomly divided into five groups and eating their usual diets, healthy volunteers (40:18 males, 22 females) ingested in two oral doses for 7 d a powder mixture containing (g SC-FOS/d): 0, G0; 2.5, G2.5; 5, G5; 10, G10; 20, G20. Stools were collected before (d1) and at the end (d8) of sugar consumption, and tolerance was evaluated using a daily chart. Total anaerobe counts were not affected by SC-FOS ingestion. Bifidobacteria counts at d8 were greater in groups G10 and G20 than in G0 and G2.5 (P < 0.05). Fecal pH did not differ among groups. A significant correlation between the dose of SC-FOS ingested and the fecal bifidobacteria counts was observed at d8 (r = 0.53; P < 0.01). Excess flatus was significantly more frequent in subjects consuming G20 than in those consuming G0, G2.5 or G5 (P < 0.05), and more intense in G20 than in G0 and G5 groups (P < 0.05). In conclusion, the optimal and well- tolerated dose of SC-FOS that significantly increased fecal bifidobacteria in healthy volunteers consuming their usual diet is 10 g/d.