Vitamin D and Influenza: Immunological Insights and Therapeutic Potential for Respiratory Health

Abstract Influenza remains a significant global public health challenge, consistently contributing to high morbidity and mortality rates. Emerging research suggests that vitamin D plays a crucial role in modulating immune responses, a finding that may have implications for the prevention and control of influenza. In this review we explored the mechanisms through which vitamin D enhances both innate and adaptive immunity, emphasizing its role in managing inflammation and antiviral defenses, and we explored the current research on the immunomodulatory effects of vitamin D, highlighting its potential protective benefits against respiratory infections like influenza. Vitamin D, immunological modulation, influenza, viral infections, cytokine regulation, innate immunity, adaptive immunity, and respiratory viruses were among the keywords used, either singly or in combination, to search the PubMed, Web of Science, Scopus, and Google Scholar databases for this research. The inclusion criteria were full-length research publications published within the previous 12 years, observational studies, in vitro studies, and studies involving humans or animals, with the exception of groundbreaking earlier works that provided fundamental insights into the function of vitamin D in immunity. The capacity of vitamin D to regulate cytokine production, boost antimicrobial peptide activity, and influence cellular immune responses may help mitigate the severity of influenza infections and related complications, such as cytokine storms. Evidence from randomized trials and observational studies further supports the role of vitamin D supplementation in reducing the incidence and severity of influenza. Although these findings highlight the therapeutic promise of vitamin D for influenza management, further investigation is needed to address existing knowledge gaps before making clear recommendations for the use of vitamin D in viral respiratory infections.