Not All Plants Are Equal: Diet Quality and Inflammation in Vegans and Vegetarians in Urban Poland

Background: Accumulating evidence suggests that dietary factors may affect cardiometabolic health, but the associations between the quality of plant-based diets and chronic-low grade inflammation have been insufficiently explored. The aim of this study was to examine the association between dietary indices and inflammatory markers in the studied cohort of vegans and vegetarians living in urban Poland. Methods: The study population comprised 198 individuals (mean age 33.6 yrs) including vegans (VG; n = 50), vegetarians (VN; n = 101) and omnivores (OV; n = 47). The following methods were used in this analysis: a questionnaire interview, anthropometric measurements and blood sample collection. Dietary patterns were evaluated using the Food Frequency Questionnaire and overall plant-based diet index (PDI) and healthful plant-based index (hPDI) were used to define adherence to plant-based dietary patterns. Results: Vegans had substantially lower hsCRP concentration and lymphocyte counts than VN and OV (p < 0.05). IL-6 concentrations, as well as total WBC, neutrophils, and lymphocytes counts, were significantly higher in OV compared to the other groups. In the overall study population, higher intake of plant-based foods was associated with lower mean levels of hsCRP, IL-6, glucose, lipids, neutrophil, lymphocyte, and total WBC counts (p < 0.05). Among vegetarians, higher consumption of healthful plant-based foods was associated with lower levels of total cholesterol, triglycerides, and selected inflammatory biomarkers. Conclusions: Our research indicates that the quality of plant-based diets is a critical determinant of cardiometabolic and inflammatory health. Importantly, eliminating animal products alone does not guarantee health benefits; rather, the composition and quality of plant-based foods are key.