In vitro digestion and fermentation combined with microbiomics and metabolomics reveal the mechanism of superfine yak bone powder regulating lipid metabolism by altering human gut microbiota

•Effects of superfine YBP on gut microbiota was evaluated by microbiome and metabolome.•Size reduction during digestion allowed superfine YBP to release more Ca2+ than CaCO3.•Indigestible YBP increased the relative abundances of gut Megasphaera and Megamonas.•Indigestible YBP was associated with greater production of gut short-chain fatty acids.•Indigestible YBP was associated with up-regulation of favorable lipid-related metabolites. The effects of superfine yak bone powder (YBP) on human gut microbiota (HGM) were investigated by in vitro digestion and fermentation combined with microbiomics and metabolomics. Results showed that size reduction and protein structural degradation during digestion allowed superfine YBP to release more Ca2+ than CaCO3 powders with similar particle size. Moreover, the indigestible YBP further influenced HGM and was associated with increased occurrence of beneficial bacteria such as Megasphaera spp., Megamonas spp., Acidaminococcus spp., and Prevotella spp. The altered HGM was associated with greater production of short-chain fatty acids with 4–6 carbon atoms. Furthermore, the indigestible YBP was associated with up-regulation of many lipid-related metabolites, including taurine, secondary bile acids, saturated long-chain fatty acids, and ω-3/ω-6 polyunsaturated fatty acids, which modulated favorably lipid metabolic pathways. These findings implied the potential activity of superfine YBP as a food fortifier in favorably altering HGM community structure and regulating lipid metabolism.