Vitamin D Found to Strengthen Defense Against COVID-19 and Influenza, and Prevents Long COVID
Nikhil Prasad Fact checked by:Thailand Medical News Team Feb 16, 2026 1 hour, 27 minutes ago
Medical News: A major new scientific review has revealed that vitamin D plays a powerful and complex role in strengthening the body’s immune defenses against serious viral infections such as COVID-19, long COVID, and influenza. Researchers found that maintaining adequate vitamin D levels may help reduce disease severity, improve recovery, and enhance the body’s ability to fight respiratory viruses.
Scientists discover vitamin D strengthens immune defenses against COVID-19, long COVID, and influenza
The research was conducted by scientists from the Faculty of Medicine and Biological Sciences at Stefan cel Mare University of Suceava in Romania, the Suceava Emergency Clinical County Hospital in Romania, and the Department of Clinical Pharmacy and the Department of Quantitative and Computational Biology at the University of Southern California in the United States. This
Medical News report highlights the critical findings and explains why vitamin D has become a focus of global health research.
Vitamin D Activates Powerful Antiviral Defenses
Scientists explained that vitamin D functions as more than just a nutrient. It acts as a hormone that directly regulates the immune system. One of its key roles is stimulating immune cells such as macrophages and natural killer cells, which identify and destroy viruses. Vitamin D also triggers the production of antimicrobial peptides such as cathelicidin and defensins, which can directly attack and neutralize viruses before they spread.
In addition, vitamin D strengthens the body’s protective barriers, especially in the respiratory tract. These barriers act as the first line of defense against airborne viruses, helping prevent viral entry into lung tissue. Vitamin D also supports immune balance by reducing excessive inflammatory reactions that can cause tissue damage.
Low Vitamin D Linked to Severe COVID 19 Outcomes
The review found consistent evidence that individuals with vitamin D deficiency face a greater risk of severe COVID-19 outcomes. Studies showed that patients with lower vitamin D levels were more likely to require hospitalization, intensive care, and mechanical ventilation. They also faced higher risks of prolonged illness and complications.
Vitamin D may also influence how the virus interacts with ACE2 receptors, which are used by SARS-CoV-2 to enter human cells. By regulating immune responses and reducing harmful inflammation, vitamin D may help limit tissue damage and improve survival outcomes. However, researchers emphasized that while associations are strong, more clinical trials are needed to confirm direct cause-and-effect relationships.
Emerging Evidence Shows Role in Preventing Long COVID
Researchers also found growing evidence that vitamin D deficiency may contribute to long COVID, a condition in which symptoms persist long after initial infection. Patients with lower vitamin D levels appear more likely to experience prolonged fatigue, respiratory issues, and inflammator
y symptoms.
Vitamin D’s ability to regulate immune activity and suppress chronic inflammation may help reduce the persistence of symptoms. However, scientists stressed that additional controlled trials are needed to determine whether vitamin D supplementation can directly prevent or treat long COVID.
Protective Effects Also Seen Against Influenza
The review also examined vitamin D’s role in influenza prevention. Several randomized trials and observational studies found that adequate vitamin D levels were associated with reduced infection risk and milder disease symptoms. Vitamin D enhances antiviral immune activity while also limiting excessive inflammation in lung tissue.
Although some studies showed mixed results, overall findings suggest that maintaining healthy vitamin D levels may provide modest protection against influenza and other respiratory infections, particularly in individuals who are deficient.
Global Vitamin D Deficiency Remains a Major Concern
Researchers warned that vitamin D deficiency remains extremely common worldwide. Limited sun exposure, aging, chronic illness, and poor nutrition all contribute to reduced vitamin D levels. This widespread deficiency may leave millions of people more vulnerable to infections and immune system dysfunction.
Conclusion
The study findings provide compelling evidence that vitamin D plays a vital role in regulating immune defenses and protecting against respiratory viral infections. By strengthening immune responses, enhancing antiviral activity, and reducing harmful inflammation, vitamin D may help lower the risk of severe COVID-19, long COVID, and influenza. While vitamin D should not be viewed as a standalone treatment, maintaining sufficient levels represents a safe, affordable, and practical strategy to improve immune resilience and support overall health, particularly in populations at risk of deficiency. Continued research will help clarify optimal dosing and clinical applications.
The study findings were published in the peer reviewed journal: Nutrients.
https://www.mdpi.com/2072-6643/18/4/634
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Read Also:
https://www.thailandmedical.news/articles/coronavirus
https://www.thailandmedical.news/articles/influenza-or-flu
https://www.thailandmedical.news/articles/long-covid
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