Dietary inflammatory index and its association with hematological inflammatory markers: a cross-sectional analysis in healthy and depressed individuals.

Introduction: Previous research has mainly focused on the dietary inflammatory index (DII) and its impact on serum inflammatory markers like C-reactive protein (CRP). Regarding the established connection between inflammation and depression, this study aims to examine the relationship between DII and hematological inflammatory markers in both depressed and healthy individuals separately.

Methods: The study involved 4567 participants from the PERSIAN Organizational Cohort Study in Mashhad (POCM), with 3226 classified as healthy and 429 as depressed. Blood samples were collected to analyze hematologic markers. Additionally, the depression, anxiety, and stress scale - 21 (DASS-21) questionnaire was administered to evaluate depression. The study also calculated various hematologic inflammatory markers, including platelet-to- high-density lipoprotein (HDL) ratio (PHR), platelet-to-lymphocyte ratio (PLR), monocyte-to-HDL ratio (MHR), lymphocyte-to-HDL ratio (LHR), red cell distribution width (RDW)-to-lymphocyte ratio (RLR), RDW-to-platelet ratio (RPR), and granulocyte-to-lymphocyte ratio (GLR).

Results: In the adjusted model, when healthy individuals move from an anti-inflammatory diet (tertile 1) to a pro-inflammatory one (tertile 3) adherence, the monocyte counts and LHR decreased by 25.1% [OR: 0.749 (0.578-0.972)] and 11% [OR: 0.89 (0.012-0.684)], respectively. However, the MHR level increases by 12.9% [OR: 1.129 (1.000, 1.275)].

Conclusion: In healthy individuals, a pro-inflammatory diet has been observed to decrease monocyte and LHR levels while increasing MHR. However, in individuals with depression, no correlation between these markers was found, which is a significant discovery. It is recommended that future studies with a larger sample size of individuals with depression be conducted to validate these results.