Effects of Heat-Killed Bifidobacterium breve B-3, a Postbiotic, on Muscle Mass-Related Parameters in Patients with...

Background/Objectives: Sarcopenia contributes to frailty and functional decline in older adults; however, effective adjunctive strategies remain limited. Heat-killed Bifidobacterium breve B-3 (B-3HK), a postbiotic, has shown muscle-related effects in preclinical studies; however, clinical evidence in patients with established sarcopenia is scarce. This pilot trial aimed to evaluate these clinical effects. Methods: In this 24-week randomized, double-blind, placebo-controlled trial, adults aged 50-89 years with Asian Working Group for Sarcopenia (AWGS) 2019-defined sarcopenia received B-3HK (2 × 10¹⁰ cells/day) or placebo daily. The primary outcome was the change in knee extension strength at week 24. Secondary outcomes included body composition measured using bioelectrical impedance analysis (BIA), dual-energy X-ray absorptiometry (DXA), physical performance, Eating Assessment Tool-10 (EAT-10), serum biomarkers, gut microbiota, and safety. Secondary outcomes were exploratory with nominal p-values and no adjustment for multiple comparisons. Results: Fifty participants were randomized, and 49 were included in the full analysis set. Compared with placebo, B-3HK did not significantly improve knee extension strength. Exploratory analyses showed between-group differences favoring B-3HK in the BIA-derived skeletal muscle mass index, limb muscle mass, EAT-10 score, and serum insulin-like growth factor-1 and 25-hydroxyvitamin D levels. These differences were primarily driven by the attenuation of the decline in the placebo group and were not corroborated by DXA-derived indices or functional outcomes. The gut microbiota composition did not differ between groups. No serious adverse events were observed. Conclusions: B-3HK did not improve muscle strength in patients with sarcopenia. Exploratory analyses identified nominal between-group differences in body composition and endocrine outcomes; however, these findings were unadjusted for multiplicity and should be regarded as hypothesis-generating rather than confirmatory evidence of efficacy. These data may help inform the design of future adequately powered trials, but confirmation is required before any therapeutic benefit can be inferred.