This mini-review examines the complex relationship between the gut microbiota and human health, with a special focus on its role in conditions such as inflammatory bowel disease (IBD) and cardiovascular disease (CVD). It explores how dietary patterns can affect the composition of the gut microbiota, thus contributing to the development of various diseases. The gut microbiota is crucial in the production of metabolites such as trimethylamine N-oxide (TMAO), which play a significant role in the development of both IBD and CVD. High levels of TMAO and other metabolites, such as phenylacetylglutamine, have been linked to an increased risk of CVD. The review highlights the potential of dietary interventions and therapies designed to modulate the gut microbiota in reducing these risks. Following a Mediterranean diet may offer cardiovascular protection, emphasizing the need for further research into the molecular mechanisms of diet-related changes in the microbiota.