Dietary intervention with sourdough and high-fiber breads enhances metabolic and microbial homeostasis in mice

Sourdough (WBS) and high-fiber (HFB) breads are increasingly recognized for their metabolic health benefits. In this study, sourdough bread was prepared using lactic acid bacteria mixture (SPC Health Guard™), while Roman Meal whole grain bread served as the high-fiber bread variant. A 10-week mouse feeding experiment compared their physiological, immunological, and gut microbiome effects against conventional white bread (WB). Both WBS and HFB significantly reduced postprandial blood glucose levels and serum low-density lipoprotein (LDL) cholesterol. The incremental area under the curve (iAUC) of serum glucose was reduced by 61.7  % in WBS and 42.0  % in HFB groups. Notably, magnesium absorption was enhanced in the HFB group. Colonic cytokine analysis revealed decreased expression of pro-inflammatory markers (tumor necrosis factor-α; TNF-α, interleukin-6; IL-6) and increased anti-inflammatory interleukin-10 (IL-10) in both WBS and HFB groups, suggesting immune modulation through sourdough fermentation processes. Microbiome profiling showed HFB induced more extensive changes than WBS, enriching beneficial taxa including Eubacterium coprostanoligenes, Faecalibaculum, and Parasutterella, which are linked to lipid metabolism and anti-inflammatory effects. Metabolomic analysis identified shared elevations of DL-arginine and rhamnetin in both WBS and HFB groups, while HFB uniquely modulated amino acid and unsaturated fatty acid metabolism. Additionally, HFB-fed mice exhibited significantly higher levels of short-chain fatty acids (SCFAs), particularly acetate and propionate, reflecting enhanced microbial activity. Overall, both sourdough and high-fiber breads demonstrated metabolic and anti-inflammatory benefits. However, high-fiber bread showed broader effects on gut microbiota and metabolome remodeling, emphasizing the importance of dietary fiber in promoting host-microbe interactions and metabolic health.