Figure 1. Influence of different factors on serum metabolites in health . The main factors in healthy individuals that affect serum metabolites are diet, lifestyle, genetics, clinical parameters and gut microbiota. Machine learning and gradient-boosted decision trees12 (GBDT) showed that diet and the gut microbiota along clinical parameters are the highest predictive factors. There is a close relationship between intestinal microbiota, serum metabolites and immune cells.