Methodological concerns in the association between gut microbiota and sarcopenia: from cross‑sectional associations to statistical fragility.

This commentary critically appraises the cross‑sectional study by Nasrollahizadeh et al. on gut microbiota and sarcopenia in Iranian older adults. Key limitations include; after FDR correction for twelve bacterial genera, no significant differences remained between groups; Akkermansia lost significance in sensitivity analyses; Lactobacillus showed a confidence interval including 1.00; four primer pairs lacked validation with no MIQE‑compliant efficiency data; the cross‑sectional design precludes causal inference; and no sample size justification was reported. The study offers valuable hypothesis‑generating data, but evidence remains preliminary. Future longitudinal studies with metagenomic approaches are essential.