The Long-term Intake of Milk Fat Does Not Significantly Increase the Blood Lipid Burden in Normal and High-fat Diet-fed Mice

After 10 weeks of feeding C57BL/6J mice with a normal diet (ND) or a high-fat diet (HFD), a 7-week intervention with milk fat and whole milk was conducted to assess their long-term effects on host blood lipid levels. The results showed that milk fat and whole milk did not significantly elevate low-density lipoprotein cholesterol (LDL-C) in either ND- or HFD-fed mice. In ND mice, milk fat and whole milk improved gut microbiota diversity and Amplicon Sequence Variants. Key bacterial genera, such as , , and , were identified as bidirectional regulators of LDL-C and high-density lipoprotein cholesterol (HDL-C). Six unique metabolites were also linked to LDL-C and HDL-C regulation. Furthermore, an optimized machine learning model accurately predicted LDL-C (² = 0.96) and HDL-C (² = 0.89) based on gut microbiota data, with 80% of the top predictive features being gut metabolites influenced by milk fat and whole milk. These findings indicate that the long-term intake of milk fat does not significantly increase the blood lipid burden, and machine learning algorithms based on gut microbiota and metabolites offer novel insights for early lipid assessment and personalized nutrition strategies.