Prebiotic effect of fructo-oligosaccharide supplemented term infant formula at two concentrations compared with unsupplemented formula and human milk.

BACKGROUND Human milk components, including oligosaccharides, affect the gastrointestinal flora of infants. Previous studies in adults have demonstrated that fructo-oligosaccharides increase potentially beneficial fecal bacteria, including bifidobacteria. The purpose of this study was to determine the prebiotic effect of infant formula supplemented with fructo-oligosaccharides. METHODS Healthy term infants 2 to 6 weeks of age were enrolled in a 5-week, prospective, randomized, crossover, single-site study with a nonrandomized human milk comparator group. Washout weeks preceded and followed a week of feeding with fructo-oligosaccharide-supplemented formula (1.5 or 3.0 g/L). Stool specimens were quantitatively cultured weekly for bacteroides, lactobacilli, bifidobacteria, clostridia and enterococci and were tested for Clostridium difficile toxin. RESULTS Seventy-two of 87 infants completed the trial; 58 were formula fed and 14 were human milk fed. Mean counts of bifidobacteria and lactobacilli were similar in all groups at entry and no group experienced a significant change in counts with fructo-oligosaccharide supplementation. After 7 days of fructo-oligosaccharide supplementation the bifidobacteria counts were greater in the 1.5 g/L fructo-oligosaccharide formula group than in the human milk fed or 3.0 g/L fructo-oligosaccharide formula groups. Formula-fed infants had higher counts of enterococci and bacteroides before fructo-oligosaccharide supplementation, and these counts did not change after supplementation. Clostridium counts increased 7 days after supplementation in the 1.5 g/L fructo-oligosaccharide formula group (P = 0.0356). No human milk fed infants had C. difficile toxin in stools. Fructo-oligosaccharide (3.0 g/L) supplementation resulted in more frequent and significantly softer stools. CONCLUSIONS Infant formula supplemented with 1.5 or 3.0 g/L fructo-oligosaccharides was safe but had minimal effect on fecal flora and C. difficile toxin.