Comparison of dietary inflammatory index and inflammatory biomarkers between vegetarians and omnivores in Chinese population

Most previous studies on the association between vegetarian diet and inflammation have used only one inflammatory biomarker e.g., C-reactive protein (CRP) and the findings were generally inconsistent. Therefore, we conducted a cross-sectional study to investigate the correlation between diet and inflammation in Chinese vegetarians using dietary indices and multiple inflammatory biomarkers. 279 vegetarians and omnivores of the same sex and age recruited in Shanghai, 2016. 24-h dietary review questionnaire was collected and used to calculate Dietary inflammatory index (DII) and Energy-adjusted inflammatory index (E-DII) of both groups. In addition, energy intake matched vegetarian and omnivore recipes were designed by registed dietitions and used to calculate a theoretical DII. Five serum inflammatory biomarkers CRP, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), neutrophil-lymphocyte ratio (NLR), and platelet-lymphocyte ratio (PLR) were measured. We found that vegetarians had significantly lower E-DII and theoretical DII than omnivores (P < 0.001). In contrast, the raw DII of vegetarians was almost the same with that of omnivores, probably due to lower energy intake in vegetarians than in omnivores (1367.97 ± 479.75 vs. 1724.78 ± 568.13, P < 0.001). Levels of TNF-α, IL-6, NLR and PLR were significantly higher in vegetarians than in omnivores while no statistical differences were found in CRP. In conclusion, a theoretical vegetarian diet with adequate energy intake as well as a balanced dietary intake showed good anti-inflammatory effects, though this was not fully reflected in vegetarian population in the real world, probably due to insufficient energy intake in the vegetarian population.