From urban to alpine: environmental microbial transfer in urban adults – the ALM Study

Background: Urbanization is linked to reduced microbial exposure, increased prevalence of lifestyle-related diseases, and diminished psychological resilience. In contrast, traditional alpine farming environments offer high biodiversity and low pollution, potentially promoting restorative health effects. The ALM Study (ALpine Farming and Human Nasal Microbiome Diversity) explored the feasibility and physiological impact of a 7-day immersion in such an environment among previously unexposed (“Alm-naive”) individuals. Methods: This prospective, single-arm feasibility study was conducted in the Riedingtal Valley, Austria. Twenty-two healthy adults (median age: 30.5 years), with no prior agricultural exposure, participated in a 7-day immersive intervention involving daily alpine farming activities. Biological (nasal swabs, venous blood), physiological (VO₂max), and psychological (WHO-5 psychological wellbeing index, EQ-5D VAS, NR-6) data were collected immediately before and after the intervention. The primary outcome was the change in nasal microbiome diversity (16S rRNA gene amplicon sequencing); secondary outcomes included hematological markers, lipid metabolism, inflammatory parameters, and wellbeing scores. Pre-post changes were analyzed using Wilcoxon signed-rank tests. Results: Nasal microbiome analysis revealed significant increases in species richness and evenness (p < 0.001). In addition, descriptive analyses indicated changes in relative phylum-level composition, with reduced Proteobacteria dominance and variable increases in Firmicutes and Actinobacteriota. Hematocrit (+3.1%, p = 0.01), reticulocyte count (+0.39%, p < 0.001), and platelet count (+27 G/L, p = 0.02) increased significantly, suggesting erythropoietic and immunological activation. Additionally, activation of the immune system became evident, as reflected by a slight but significant rise in CRP (+0.04 mg/dL, p = 0.01), in the absence of concurrent changes in IL-6 or leukocyte counts. Total cholesterol (−8.08 mg/dL, p = 0.02) and non-HDL cholesterol (−2.00 mg/dL, p = 0.01) decreased, VO₂max showed a positive trend (+3.43 mL· kg⁻¹·min⁻¹, p = 0.07). WHO-5 psychological wellbeing scores improved markedly (+12%, p < 0.001), while other psychometric scales remained unchanged. Conclusion: A 1-week immersion in a biodiverse alpine environment was associated with measurable changes in the nasal microbiome, hematological and metabolic profiles, and psychological wellbeing. These findings support both the feasibility and the potential health relevance of short-term, nature-based interventions for urban populations.