A high-fibre snack containing Lacticaseibacillus rhamnosus GG for healthy adults: a randomised, double-blind, placebo-controlled crossover trial.

Probiotics have gained increasing evidence for their roles in health and disease. Microencapsulation can improve the consistency and efficacy of probiotic-fortified foods by enabling safer delivery to target regions of the gastrointestinal tract. We evaluated a probiotic snack bite containing microencapsulated Lacticaseibacillus rhamnosus GG. Twenty-five healthy adults consumed one snack daily for 28 days, then a 7-day washout, followed by crossover. Outcomes included gastrointestinal health analysis, bowel movement ease and frequency, bloating, overall gut comfort, shotgun metagenomics and systemic biomarkers of barrier, brain function and inflammation. Compared with the lower-fibre control snack, the probiotic snack was associated with easier bowel movements and fewer constipation reports at end of period, while bloating remained low in both periods. However, because the products differed in nutritional composition, these findings cannot be attributed to L. rhamnosus GG alone inflammatory and barrier biomarkers did not differ between treatments and stayed within healthy ranges. In an exploratory subgroup with elevated baseline serotonin, end-of-period serotonin was lower after the probiotic-containing snack than after the control snack, whereas brain-derived neurotrophic factor was unchanged. Daily intake of microencapsulated Lacticaseibacillus rhamnosus GG was well tolerated and was associated with exploratory difference in bowel habit and serum serotonin in a subgroup, without detectable changes in systemic inflammation or barrier biomarkers.