Lacto-fermented vegetables as dynamic food ecosystems: emerging mechanisms along the microbiome-gut-brain axis

Lacto-fermented vegetables (LFVs) are traditional foods produced through the microbial transformation of plant materials by lactic acid bacteria, with additional contributions from yeasts and other microorganisms. Fermented foods have been increasingly investigated for their potential modulation of the microbiome-gut-brain axis. This research has mainly focused on dairy fermentations, leaving LFVs largely underexplored. This mini review examines LFVs and their emerging mechanisms within the microbiome-gut-brain axis (MGBA). It emphasizes their character as evolving microbial ecosystems and as sources of bioactive metabolites. During the fermentation process, ecological succession drives the production of a variety of compounds, including organic acids, amino acids and lipid derivatives, transformed phytochemicals, structural microbial components, and micronutrients. Many of these compounds have plausible connections to MGBA routes. These links include modulation of the intestinal barrier, local and systemic immune responses, enteroendocrine signaling, and autonomic/vagal pathways. Particular focus is given to the small intestine as an early signaling interface between metabolites and host physiology. Scientific evidence of the beneficial effects of LFVs on human health is limited. Existing studies show improvement in gastrointestinal symptoms, cardiometabolic risk factors and gut microbial function. Studies connecting LFVs to neurological and psychological health are lacking. We propose understanding LFVs as complex food ecosystems whose effects on host physiology arise from interactions among microorganisms, metabolites, environmental conditions, and host responses. Future research integrating food multi-omics, microbiome analyses, immune profiling, neuroendocrine measurements, and clinical outcomes may help clarify the role of LFVs in MGBA and support the development of targeted fermentation-based nutritional strategies for intestinal, immune, and neuropsychological health.