Xylo-oligosaccharides alone or in synbiotic combination with Bifidobacterium animalis subsp. lactis induce bifidogenesis and modulate markers of immune function in healthy adults: a double-blind, placebo-controlled, randomised, factorial cross-over study

This was a double-blind, placebo-controlled, randomised, factorial cross-over study in healthy adults aged 25 to 65 years with BMI 20 to 30 kg/m2. Forty-four volunteers were recruited and 41 completed the trial; active-arm analyses were reported across treatment periods with some outcome-specific variation in analyzable n.

Active oral supplementation was given for 21 days per treatment period in a double-blind crossover design. Xylo-oligosaccharides (XOS) were administered at 8 g/day, Bifidobacterium animalis subsp. lactis Bi-07 at 10^9 CFU/day, and the synbiotic arm combined 8 g/day XOS plus 10^9 CFU/day Bi-07; all were provided in powder sachets to be dissolved in a drink.

Overall, XOS and Bi-07 modulated gut microbiota and immune markers in healthy adults, with the clearest benefits seen for XOS and some additional additive effects in the synbiotic arm. XOS increased bowel movements (P=0.005), increased fecal bifidobacterial content (P=0.008), and increased fasting HDL cholesterol (P=0.005; average increase 0.07 mM), while also improving vitality and happiness and lowering some immune markers including CD16/56 expression and IL-10 secretion. Bi-07 increased fecal B. lactis and changed immune readouts, including lower IL-4, higher IL-6, and reduced salivary IgA; the synbiotic reduced CD19 expression and analgesic use but did not show clear synergistic enhancement of microbiota beyond the individual components. No notable increase in adverse events was reported.

The study was small, with 44 recruited and 41 completing the trial, and it used short 21-day treatment periods. Several outcomes had incomplete or treatment-period-specific analyzable samples, and HDL analysis was limited to the first treatment period because of carry-over effects. The population was restricted to generally healthy adults, which limits generalizability.