This is down to its anti-inflammatory and immunoregulatory properties, which are crucial for the activation of immune system defenses.
Vitamin D is known to enhance the function of immune cells, which is important for protection against infection, disease and immune-related disorders.
People with low vitamin D levels are more likely to develop respiratory diseases, including tuberculosis, asthma, and chronic obstructive pulmonary disease (COPD), as well as viral and bacterial respiratory infections.
source: express.co.uk