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In this double-blind, randomized, placebo-controlled study, we investigated the effect of an infant milk formula with 6 g/L short-chain galacto- and long-chain fructo-oligosaccharides [(scGOS/lcFOS) ratio 9:1] on the development of the fecal secretory immunoglobulin A (sIgA) response and on the composition of the intestinal microbiota in 215 healthy infants during the first 26 wk of life. The infants received breast milk or were randomized to receive an infant milk formula with or without scGOS/lcFOS. Stool samples were collected after 8 and 26 wk of intervention. The concentration of fecal sIgA was determined by ELISA, and the composition of the intestinal microbiota was determined by quantitative fluorescent in situ hybridization. The scGOS/lcFOS group and the control group were compared in the statistical analysis. A breast fed group was included as a reference. In total, 187 infants completed the study. After 26 wk of intervention, in infants that were exclusively formula fed, the concentration of sIgA was higher (P < 0.001) in the scGOS/lcFOS group (719 microg/g) than in the control group (263 microg/g). In addition, the percentages of bifidobacteria were higher in the scGOS/lcFOS group (60.4%) than in the control group (52.6%, P = 0.04). The percentages of Clostridium spp. were 0.0 and 3.27%, respectively (P = 0.006). In conclusion, an infant milk formula with 6 g/L scGOS/lcFOS results in higher concentrations of fecal sIgA, suggesting a positive effect on mucosal immunity.

Objectives Breast-fed infants have relatively high proportions of faecal bifidobacteria. This bifidogenic microbiota is at least partly explained by the high levels of prebiotic oligosaccharides in human milk. The present study aimed at testing the effect of solid foods with added prebiotic galacto- and fructo-oligosaccharides (GOS/FOS) on the composition of the intestinal microbiota of fully formula-fed infants during the weaning period. Methods The study was a double-blind, randomised trial with an intervention period of 6 weeks. Infants aged 4 to 6 months who were about to start consuming solid foods were randomised to receive either weaning products with a mixture of GOS/FOS or control weaning products with maltodextrin. After an adjustment period, the presented daily dose of GOS/FOS was 4.5 g. Total numbers of bacteria and bifidobacteria in faecal samples were analysed with fluorescent in situ hybridization. Results Thirty-five infants were included in the study, and 20 infants were included in a per-protocol analysis. In the GOS/FOS group, the faecal percentage of bifidobacteria significantly increased from 43% to 57% (P = 0.031) from week 0 to week 6, but did not significantly change in the control group (36% and 32%, respectively; P = 0.387). The change in the percentage of bifidobacteria between week 0 and week 6 in the GOS/FOS was significantly different from this change in the control group (P = 0.026). Conclusions We conclude that addition of GOS/FOS to solid foods induces an increase in the faecal proportion of bifidobacteria in the intestinal microbiota of fully formula-fed infants with an established, mixed-type microbiota in the weaning period.

Secretory immunoglobulin A (SIgA) plays an important role in the defence of the gastrointestinal tract. The level of faecal SIgA antibody is associated with increased neutralization and clearance of viruses. Formula-fed infants who lack the transfer of protective maternal SIgA from breast milk may benefit from strategies to support maturation of humoral immunity and endogenous production of SIgA. We aimed at studying the effects of standard, prebiotic and probiotic infant formulas on the faecal SIgA levels. At birth, infants of whom the mother had decided not to breastfeed were allocated to one of three formula groups in a randomized, double-blind fashion. Nineteen infants received standard infant formula; 19 received prebiotic formula containing a specific mixture of 0.6 g galacto-oligosaccharides (GOS)/fructo-oligosaccharides (FOS)/100 ml formula and 19 received probiotic formula containing 6.0 × 109 cfu Bifidobacterium animalis/100 ml formula. Faecal samples were taken on postnatal day 5, day 10, wk 4 and every 4 wk thereafter until wk 32. SIgA in faeces was determined by an enzyme-linked immunosorbent assay. During the intervention, infants fed on prebiotic formula showed a trend towards higher faecal SIgA levels compared with the standard formula-fed infants reaching statistical significance at the age of 16 wk. In contrast, infants fed on the probiotic formula showed a highly variable faecal SIgA concentration with no statistically significant differences compared with the standard formula group. Formula-fed infants may benefit from infant formulas containing a prebiotic mixture of GOS and FOS because of the observed clear tendency to increase faecal SIgA secretion. Adding viable B. animalis strain Bb-12 to infant formula did not reveal any sign for such a trend. Secretory immunoglobulin A (SIgA) is one of the most abundant immunoglobulin in the human body and is the predominant immunoglobulin in mucosal surfaces. SIgA plays a key role in the gastrointestinal defence mechanism against dietary and microbial antigens. It inhibits adherence and invasion of potentially harmful antigens into mucosal tissues and neutralizing toxins and virulence factors from microbial pathogens (1). It is well established that the level of faecal SIgA antibody correlates with higher virus-neutralizing capacity and increased viral clearance (2). IgA deficiency in humans is one of the most common immunodeficiencies and is associated with frequent gastrointestinal infections (3). There is accumulating evidence that the intestinal SIgA production is highly influenced by the intestinal microflora. Indeed, the development of the IgA-producing plasmablasts (intermediate stage of the development of a B-lymphocyte into IgA-producing plasma cell) in the intestinal mucosa seems to be affected by components of the intestinal microflora (4). During the first few weeks after birth, the mucosal humoral immunity is not in a mature state. Passive immunity in this phase is provided by breast milk, which contains high levels of SIgA and antimicrobial peptides. SIgA in breast milk are mainly directed against the mother's previous and current gut microflora (5). Breast milk SIgA protects the maternal mammary gland against mastitis, protects the neonatal mucosa against early exposure to microbes and limits bacterial translocation. In breast milk, SIgA levels are highest during the first days after birth (human colostrum contains 2¿5 mg SIgA/ml) and then gradually decrease to 0.5¿1 mg/ml (6). Although many factors may influence SIgA survival in the large intestine, measuring SIgA levels in faeces gives a good representation of the amount available in the colon (7). In the first 2¿4 wk of life, the concentration of IgA in faeces of breast-fed infants is substantially higher compared to that found in formula-fed infants in whom SIgA is basically undetectable (8). Between 4 wk and 6 months of life, faecal IgA concentrations in both breast-fed and formula-fed infants converge towards similar levels. At age 1¿2 yr, when weaning is completed, the production of SIgA reaches adult levels (9). It is generally recognized that intestinal microflora may play an active role in the ontogeny of the newborn's immune response. Studies performed in germ-free animals showed that colonization leads to the development of the gut-associated lymphoid tissue, including SIgA secretion in the intestine (10, 11). Moreau and Baforiau-Routhiau have shown that in particular bifidobacteria in the infant's intestine are important for the synthesis of IgA against viral enteropathogens. Therefore, they suggested that foods promoting bifidobacteria in the intestine could be instrumental in stimulating endogenous SIgA production and hence promote resistance in infants (12). Although the mechanism of immune stimulation by bifidobacteria is largely unknown, it is thought that the cell walls of Gram-positive bacteria, which are rich in peptidoglycans, may play a role. Both prebiotics and probiotics change the intestinal microflora by increasing the numbers of bifidobacteria and lactobacilli. Bifidobacteria and lactobacilli have various beneficial effects in health and disease, including maintenance of intestinal barrier integrity and mucoprotection, stimulation of protective immune responses and protection against harmful pathogens. During the last decade, interest on the immune effects of probiotics has increased markedly. Experimental studies showed that probiotics have strain-specific effects on immunity, for instance in the prevention or treatment of allergic disease. The reported effects of probiotics include enhancement of gut barrier function and induction of regulatory and pro-inflammatory immune responses (13). Additionally, several studies reported that supplementation of food with prebiotics or probiotics can increase SIgA response to viruses and bacteria. However, most of these studies were performed in animals or in vitro and the mechanisms for this immune stimulation are largely unknown (14¿18). As infants not receiving breast milk have lower SIgA levels during the first months of life, they would potentially benefit from strategies to support maturation and production of mucosal SIgA. Therefore, we studied the effects of infant formula with added probiotics or prebiotics on the faecal SIgA levels in infants. We hypothesized that infants on probiotics or prebiotics will have higher levels of total faecal SIgA compared with infants fed on a standard, unsupplemented infant formula

Adding prebiotics or probiotics to infant formula to improve the intestinal flora of formula-fed infants is considered to be a major innovation. Several companies have brought relevant formulations onto the market. However, comparative data on the effects of pre- and probiotics on the intestinal microflora of infants are not available. The present study aimed to compare the effects of infant formula containing a mixture of galacto- and fructo-oligosaccharides or viableBifidobacterium animalison the composition and metabolic activity of the intestinal microflora. Before birth, infants were randomised and double blindly allocated to one of three formulas. The prebiotic (GOS/FOS) group (n19) received regular infant formula supplemented with a mixture of galacto-oligosaccharides and fructo-oligosaccharides (6g/l). The probiotic (Bb-12) group (n19) received the same formula supplemented with 6·0×1010viable cells ofB. animalisper litre. The standard group (n19) received non-supplemented regular formula. A group of sixty-three breast-fed infants was included as a reference group. Faecal samples were taken at postnatal day 5 and 10, and week 4, 8, 12 and 16. Compared with the groups fed Bb-12 and standard formula, the GOS/FOS formula group showed higher faecal acetate ratio (69·7% (sem 2·7), 69·9% (sem 3·9) and 82·2% (sem 5·3);PP

Human milk is regarded as the best nutrition for infants. However, when breastfeeding is not possible, desirable or sufficient, infant milk formulas serve as an adequate substitute for human milk. They have been designed to provide infants with the required nutrients for optimal growth and development. In addition, infant milk formulas are now increasingly resembling human milk, for example in the area of bifidogenic effects. This review describes current trends in the design of infant formulas. Topics that will be discussed are long-chain polyunsaturated fatty acids, triacylglycerol palmitate, optimal protein concentration, the use of hydrolysed and soy protein, nucleotides and pre- and probiotics.

Fructo-oligosaccharides (FOS) are widely used in commercial food products. Most studies on FOS concern the health benefits, but some negative effects were recently reported concerning thefaecal cytotoxicity and excretion of mucin-type oligosaccharides in combination with a Ca-restricted diet. The present study was performed to investigate whether these effects of FOS are observed in adults consuming a regular diet unrestricted in Ca. The study was a randomised, double-blind, placebo-controlled crossover trial, involving eleven healthy adults, who consumed 25–30g FOS or maltodextrin (control) in a random order for 2 weeks in addition to their regular diet. Stools were collected for analysis of pH and SCFA (as markers of fermentation), for the assessment of faecal water cytotoxicity, and for the analysis of alkaline phosphataseactivity (as a marker of epithelial cell turnover) andO-linked oligosaccharides (to estimate the excretion of mucin-type oligosaccharides). FOS consumption significantly altered bacterial fermentation (increased percentage of acetate, decreased percentage of butyrate) and tended to decrease stool pH. Furthermore, FOS consumption resulted in a significantly higher stool frequency and in significantly more complaints of flatulence. No significant differences between the control and FOS period were observed in the mean cytotoxicity of faecal water (37·5 (sem 6·9) % v. 18·5 (sem 6·9) % P=0·084), in mean alkaline phosphatase activity (27·7 (sem 2·9) v. 24·6 (sem 3·2) U/g dry faeces; P=0·496) or in the mean excretion of mucin-type oligosaccharides (49·9 (sem 4·0)v. 53·5 (sem 4·3) mg/g dry faeces; P=0·553). We conclude that dietary FOS in a dose up to 25–30g/d altered the bacterial fermentation pattern but did not affect faecal cytotoxicity or the faecal concentration of mucin-type oligosaccharides in human adults consuming a regular diet.

Background and aims: Gastrointestinal (GI) proteases are best known for their function in protein digestion. However, GI luminal serine protease activity is also associated with inflammation, pain and visceral hypersensitivity via activation of protease-activated receptor-2 (PAR-2). An infant milk formula comprising product fermented by Streptococcus thermophilus 065 and Bifidobacterium breve C50 has previously been reported to improve gut comfort in infants with digestive problems. Here, the effect of this fermented formula (Lactofidus) on proteolytic activity was investigated at the terminal ileum. Methods: The fermented formula and a non-fermented standard formula were tested in three-week-old piglets (N=6) fitted with a T-cannula. Each formula was provided in a Latin square design. Ileal digesta were collected during eight hours and subsequently analyzed for total proteolytic activity and protein digestibility. Proteolytic activity was further characterized either by specific substrates or inhibitors as serine protease, trypsin, or chymotrypsin activity. Results: Fermented formula yielded a more than threefold lower total proteolytic activity at the terminal ileum compared to standard formula (477 ± 84 ·103 and 1599 ± 343 ·103 units/8h, respectively). This proteolytic activity was found to be mainly constituted by the pancreatic serine proteases trypsin and chymotrypsin. Despite lower proteolytic activity in the fermented formula, protein was fully digested. Conclusions: The fermented formula causes lower exposure of the small intestine to pancreatic serine proteases. This could contribute to improved gut comfort via diminished activation of PAR-2, which could be particularly beneficial in infants with digestive problems.