An interesting study recently looked at the relationship between vitamin D levels and 'respiratory infections' in 6,789 British adults . The researchers, from University College London, found that vitamin D levels and infection risk had a linear relationship, which in this case meant that the higher levels of vitamin D were, the lower the risk of infection.
This research looked at the relationship between vitamin D levels and risk of viral respiratory tract infection such as cold and flu. It assessed blood levels of vitamin D and viral infection in almost 200 American men and women throughout last autumn (fall) and winter.
Some interesting findings from this study were:
This study showed that as vitamin D levels rose, so did resistance to infection. However, the benefit appeared to level off at about 38 ng/ml (which is why this figure was chosen as a cut-off in the analysis).
These studies are 'epidemiological' in nature, so they cannot be used to prove 'causality' (i.e. that higher vitamin D levels protect against viral infection), only that the higher vitamin D levels are associated with improved resistance to infection. However, there is at least a plausible mechanism through which vitamin D might do this, as the authors of this study point out:
Vitamin D has known effects on the immune system. The production of the antimicrobial peptides cathelicidin by macrophages and β-defensin by endothelial cells is upregulated by vitamin D. These peptides may be involved in the direct inactivation of viruses.
Everyone should try to optimize their vitamin D levels to protect against infection and preserve health. Regular exposure to sunlight in the ideal way to do this, but when this is not possible, for example during the winter, then supplementation with a high quality vitamin D3 supplement is the next best thing.
Research Paper Details:
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