Dietary Nutrients, Gut Microbiota, and Cardiac Function: From Metabolic Mechanisms to Clinical Applications

Background: The heart depends on a continuous and flexible energy supply from fatty acids, glucose, and other substrates. Emerging evidence shows that gut microbiota-derived metabolites—such as trimethylamine-N-oxide (TMAO), short-chain fatty acids (SCFAs), secondary bile acids, indoles, phenylacetylglutamine (PAGln), and branched-chain amino acids—modulate cardiac metabolism and function. Although clinical evidence linking these metabolites to cardiovascular outcomes is expanding, most data remain associative, with limited causal or interventional proof. Methods: A comprehensive narrative review was conducted (PubMed 2010–2025) to integrate preclinical, clinical, and Mendelian randomization studies on microbiota-derived metabolites and cardiovascular disease, complemented by evidence from dietary and interventional trials. Results: Gut-derived metabolites regulate mitochondrial energetics, inflammatory, immune system, and oxidative pathways, and endothelial and platelet activation. Elevated plasma TMAO and PAGln levels are often associated with adverse cardiovascular outcomes, while SCFAs and indole derivatives may related to protective effects. However, findings across cohorts remain heterogeneous, largely due to differences in diet, renal function, and analytical methods. Dietary patterns rich in fiber and plant-based nutrients favor beneficial metabolite profiles, underscoring the nutritional modulation of the gut–heart axis. Conclusions: The diet–microbiota–metabolite axis represents an emerging pathway connecting nutrition to cardiovascular health. Translating this knowledge into prevention and therapy will require large-scale randomized studies and integrated multi-omics approaches. Dietary modulation of microbial metabolism may ultimately become a novel strategy for cardiometabolic protection.