Vitamin D Supplementation Enhances Hematologic Recovery in Vitamin D-Deficient Adults With Iron Deficiency Anemia

Iron deficiency anemia (IDA) is the most common form of anemia worldwide. Emerging evidence suggests that vitamin D (VD) and micronutrient deficiencies may impair erythropoiesis and iron metabolism. However, clinical data on their combined effects in the Indian population are limited.

This study evaluated the impact of adjunctive VD supplementation alongside iron-containing micronutrient supplements and additional minerals (oral IDA therapy) in VD-sufficient (VD-S) and VD-deficient (VD-D) adults >18 years.

IDA participants were categorized in Group I (VD-S+Fe, n=109), Group II (VD-D+Fe, n=138), and Group III (VD-D+Fe+VD, n=138). All groups received oral IDA therapy, including once-daily iron-containing micronutrient supplementation for 90 days (300 mg ferrous fumarate, folate, vitamin B₁₂), and additional minerals, while the VD-D+Fe+VD group additionally received VD supplementation (once-weekly 60,000 IU cholecalciferol during the first 6 weeks). Hematologic, iron status, VD, and related biochemical parameters were assessed at baseline and after 90 days.

All groups showed significant within-group improvements in hematologic and iron parameters over 90 days (all p < 0.05). However, improvements were greatest in the VD-D+Fe+VD group, followed by the VD-S+Fe group, and least in the VD-D+Fe group. Adjusted analysis of covariance (ANCOVA) demonstrated significantly increased hemoglobin, hematocrit, RBC count, MCV, RDW-CV, ferritin, and other parameters in the VD-D+Fe+VD group compared with both other groups. Changes in VD levels were positively associated with improvements in hemoglobin, hematocrit, red blood cell indices, ferritin, and iron and inversely associated with red cell distribution width, transferrin, and total iron-binding capacity (all p < 0.05).

VD deficiency was associated with a reduced hematologic response to iron-containing micronutrient supplementation for IDA. In participants with VD deficiency, adjunctive vitamin D supplementation in combination with the iron-containing micronutrient supplement significantly enhanced hematologic recovery compared with the iron-containing micronutrient supplement alone. These findings suggest that optimizing VD status may improve treatment outcomes in IDA.