International Journal of Preventive Medicine (Int J Prev Med)2008-78021442023050828052805ENDepartment of Nutritions, School of Public Health, Iran University of Medical Sciences, Tehran, IranDepartment of Hematology, School of Allied Medical Sciences, Tehran University of Medical Sciences, Tehran, IranDepartment of Nutritions, School of Public Health, Iran University of Medical Sciences, Tehran, IranDepartment of Nutrition, School of Public Health, Iran University of Medical Sciences, Tehran, IranNatural products and medicinal plants research center, North Khorasan University of Medical Sciences, BojnurdDepartment of Biostatsitics, School of Public Health, Iran University of Medical Sciences, TehranDepartment of Nutrition, School of Health, Golestan University of Medical Sciences, Golestan,Department of Microbiology, School of Medicine, Iran University of Medical Sciences, TehranDepartment of Clinical Biochemistry, Faculty of Medicine, Tehran University of Medical Sciences, Tehran20230508Background: Hematological inflammatory indices are currently suggested to assess systemic inflammation. This study aims to investigate a vitamin D supplementation effect on hematological indices of inflammation in rats. Method: Forty‑eight middle‑aged male rats were allocated into a normal diet (ND) group (10% fat) and a high‑fat diet (HFD) group (60% fat). The animals were fed for 26 weeks. After this period, each group was randomly divided into three subgroups, each of 8 rats: Group (1): animals were fed the ND and HFD containing 1 IU/g vitamin D for 4 months, group (2): animals were fed the ND and HFD containing 6 IU/g vitamin D for 4 months and group (3): animals were euthanized to evaluate the HFD effect. Serum 25‑hydroxyvitamin D level, white blood cell count (WBCs), platelet count, platelet crit (PCT), mean platelet volume (MPV), platelet distribution width (PDW), platelet‑to‑lymphocyte ratio (PLR), neutrophil‑to‑lymphocyte ratio (NLR), monocyte‑to‑lymphocyte ratio (MLR) were measured. Results: The HFD, significantly increased body weight, PCT, PDW, PLR, NLR, and MLR and significantly reduced serum vitamin D levels compared to the ND (P < 0.05). There was a significant decrease in food intake, MPV, PDW, and NLR after vitamin D supplementation in the ND‑fed group (P < 0.05). A significant reduction in platelet count, PCT, and MLR was observed after vitamin D supplementation in HFD‑fed rats (P < 0.05). Conclusions: In our study, some hemogram‑derived inflammatory indices were higher in the HFD‑fed group, and vitamin D supplementation lowering effects on some hematological indices were seen in both ND and HFD groups.http://ijpm.mui.ac.ir/index.php/ijpm/article/view/2805http://ijpm.mui.ac.ir/index.php/ijpm/article/download/2805/717718646