From soil to the intestinal tract: The key role of beneficial elements and probiotics in promoting health and longevity

Although soil quality and gut probiotics have been extensively accepted as critical for human health, the combined effects of soil and fecal bacteria on public health remain underexplored. This study collected soil and human fecal samples from three towns with high, medium, and low proportion of longevous populations in a well-known longevity region in Yangtze River Delta, China. Beneficial elements were detected in all soils, including selenium (0.01-0.05 mg kg⁻¹), germanium (1.07-1.44 mg kg⁻¹), boron (0.42-1.49 mg kg⁻¹), zinc (1.07-1.70 mg kg⁻¹) and manganese (38.78-43.52 mg kg⁻¹). These elements were more abundant in high-proportion region (HP) compared to medium (MP) and low (LP) proportion region (p < 0.05). Similar dominant bacteria were detected in all soils and feces, including Proteobacteria (29.93 %), Acidobacteriota (16.23 %), and Bacillus (2.25 %). Notably, positive correlations were detected between beneficial metal contents and soil bacterial abundance (p < 0.05), suggesting a role in promoting bacterial growth. Moreover, beneficial element metabolic genes, such as zupT (encoding high-affinity zinc transporter for active zinc ion transport) and mntA (encoding manganese ion transporter protein) were significantly enriched in HP soil and fecal bacteria (p < 0.05). Additionally, Source Tracker analysis indicated that 41.13 % of fecal bacteria in HP area originated from HP soil bacteria. Structural equation model indicated that soil beneficial elements significantly enhanced the relative abundance of probiotic associated genes in the dominant fecal bacteria (path coefficients of 0.869 and 0.905, respectively; p < 0.05). Together, soil-borne beneficial elements promote intestinal bacterial functionality, contributing to human health and longevity.