The Mediterranean Diet (MD) has a profound effect on Alzheimer’s disease, with cultural adaptations aiding in sustained adherence over time. It centres around olive oil, legumes, whole grains, fruits, vegetables, moderate consumption of fish and dairy, and limited intake of meat. Nutritional intervention studies reveal that the MD can lower serum lipid levels, oxidative stress, inflammation, and platelet aggregation, while also influencing hormones and growth factors associated with cancer progression. Conversely, the Western Diet (WD), which is characterized by high levels of fats, refined carbohydrates, and red meat, along with low consumption of fish, fruits, and plant-based foods, adversely affects the immune system and contributes to dysbiosis—an imbalance in gut structure and function leading to inflammation. Clinical research confirms the pivotal role of diet in shaping gut microbiota and overall health. The WD is linked to negative health outcomes, such as obesity and various non-communicable diseases (NCDs), including cancer, cardiovascular diseases, and type 2 diabetes. Chronic oxidative stress, amplified by elevated reactive oxygen species (ROS), is closely associated with degenerative conditions like Alzheimer’s disease, Parkinson’s disease, and other inflammatory and cardiovascular disorders. This dynamic is bidirectional; gut microbiota not only processes nutrients but is also significantly influenced by dietary choices. Observational studies further underscore the MD’s protective benefits against global health challenges, including cardiovascular disease (CVD), recurrent cardiac events, CVD-related mortality, metabolic syndrome, abdominal obesity, and gestational weight gain.