Abstract
INTRODUCTION: Anemia, characterized by low hemoglobin or erythrocyte levels, is a significant global health issue with severe implications for public health. Recent studies have explored the potential link between anemia and 25-hydroxyvitamin D [25(OH)D], yet the precise mechanisms remain unclear. This study aims to clarify the possible causal relationship between 25(OH)D levels and anemia risk. METHODS: We conducted a comprehensive investigation combining observational and Mendelian randomization (MR) analyses. The observational study included detailed demographic, comorbidities, and laboratory data collected from 7160 hospitalized patients in China. For the MR analysis, genetic polymorphisms were utilized to assess causal effects. RESULTS: Observational analysis revealed an inverse relationship between 25(OH)D levels and the risk of anemia, with stratified analysis indicating a nonlinear association and a threshold of 48.716 nmol/L. The MR analysis confirmed a protective causal relationship between higher 25(OH)D levels and a reduced risk of anemia. Bidirectional MR analysis found no evidence that anemia influences 25(OH)D levels. DISCUSSION: This study provides strong evidence of a causal link between increased 25(OH)D levels and a lower incidence of anemia. The findings highlight the potential role of vitamin D in anemia prevention, supporting the need for further research into vitamin D supplementation as a strategy to reduce anemia risk. CONCLUSION: Our findings support the hypothesis that higher 25(OH)D levels are causally associated with a reduced risk of anemia, suggesting vitamin D's potential role in anemia prevention and public health strategies.