Mitigating Diarrhoea-Related Inflammation in Frail Older Adults with Postbiotic-Enhanced Oral Rehydration Solution: Insights from a Randomised, Double-Blind, Placebo-Controlled Study

<b>Background/Objectives:</b> Diarrhoea in older adults can lead to dehydration and malnutrition, impaired gut barrier function, and reduced quality of life. Unresolved inflammation during diarrhoea episodes contributes to relapse and complications. This randomised study evaluated the effects of a novel oral rehydration solution (ORS) with the postbiotic ABB C22^®, known for its anti-inflammatory properties, on diarrhoea-associated inflammation in an elderly population. <b>Methods</b>: A randomised, double-blind, placebo-controlled, parallel-group trial was conducted at two hospital centres in Barcelona, Spain. Forty-seven participants aged ≥65 years with diarrhoea (<i>n</i> = 47) were randomised (1:1) to receive either ABB C22^®-enriched ORS or placebo ORS for up to 14 days. Randomization was stratified by centre using a computer-generated sequence. Participants, caregivers, and outcome assessors were blinded. Primary endpoints were changes in faecal inflammatory biomarkers (calprotectin and lactoferrin) and blood immunoglobulin A. Secondary endpoints included changes in stool consistency (Bristol Stool Scale) and treatment tolerability. <b>Results</b>: Of the 47 participants, 42 completed the trial (21 per group). At day 14, the ORS + ABB C22^® group showed greater reductions in faecal calprotectin and lactoferrin levels compared to the placebo group. Lactoferrin-positive cases were halved by day 3 in the intervention group. Stool consistency improved in both groups. No adverse events were reported in either group. <b>Conclusions</b>: ABB C22^®-enriched ORS exhibited superior anti-inflammatory effects compared to standard ORS while achieving similar improvements in stool consistency. These findings suggest that postbiotic-enriched formulations represent a promising approach to better address the management of diarrhoea which is often accompanied by gut inflammation. The study protocol was registered in ClinicalTrials.gov (NCT06738420; date: 16 December 2024).