Nutritional Determinants of Type 2 Diabetes Mellitus in the European Union: A Systematic Review

Background/Objectives: Type 2 diabetes mellitus (T2DM) represents a growing public health burden in the European Union (EU), largely driven by modifiable lifestyle factors such as diet. This systematic review aimed to synthesize observational evidence on the associations between nutritional exposures and incident T2DM across the EU-28, with a focus on regional heterogeneity and implications for EU-level nutrition policy. Methods: The review followed PRISMA 2020 guidelines and was registered in PROSPERO (CRD42020219994). Searches were conducted in different databases (PubMed, Embase, Scopus, Web of Science) identifying 23,437 records, from which 104 observational studies were included. Eligible studies involved adults (≥18 years) without T2DM at baseline and assessed dietary exposures in relation to T2DM incidence. Data extraction and methodological quality assessment were performed in duplicate using the NHLBI tool in Covidence. Results: Most included studies were cohort studies (77.9%), primarily conducted in Western, Northern, and Southern Europe. Diets characterized by high consumption of whole and minimally processed foods, such as fruits, vegetables, legumes, whole grains, and fermented dairy, consistently showed associations with lower T2DM risk. In contrast, high intake of red and processed meats, sugar-sweetened beverages, and ultra-processed foods was linked to higher risk. Adherence to Mediterranean or plant-based dietary patterns was associated with lower risk, whereas high animal-protein dietary patterns were detrimental. Conclusions: Nutritional determinants play a decisive role in shaping T2DM risk in the EU. Evidence supports prioritizing dietary patterns rich in plant-based and minimally processed foods while reducing ultra-processed and meat-based products. Tailored region-specific policies are needed to address the T2DM epidemic and guide effective prevention strategies.