Vitamin D deficiency and respiratory health: A narrative review bridging gaps in public health through innovative strategies and sustainable solutions.

Vitamin D deficiency is a global public health issue, highly prevalent in middle-income and Eastern Mediterranean countries. It is associated with increased risks of respiratory infections like COVID-19 and influenza, alongside osteoporosis and cardiovascular disease. Functioning as an immunomodulator, vitamin D enhances macrophage activity, suppresses inflammatory cytokines, and induces antimicrobial peptides. Observational studies link deficiency to a higher risk of infection, although clinical trial results are mixed. Risk factors include dark skin, older age, urban living, and reduced sun exposure. This narrative review synthesized findings from peer-reviewed literature (2000-2025) in databases such as PubMed, Scopus, and Web of Science. It focuses on addressing respiratory infections associated with vitamin D deficiency through multifaceted public health strategies. These include policy-led food fortification, biofortification, public awareness campaigns, and technological innovations to increase dietary vitamin D intake and reduce the global burden of deficiency and respiratory infection.