Vitamin D stimulates the production of antimicrobial peptides, a class of natural antibiotics. The antibacterial effect has been known for over a century. The best known example of this is the treatment of tuberculosis prior to the discovery of antibiotics. Patients were sent to sanitariums where they stayed outside on sunny porches during the day. The explanation of the beneficial effect wasn’t fully understood at the time. We now know that the increased sunlight led to increased production of vitamin D and led to some arrest or even cures of the tuberculosis because of the production of these anti-microbial peptides.
There have been reports in the past few years on the effect of vitamin D and influenza. 7) UPDATE ON VITAMIN D–2010 (from this web site) noted that the terrible pandemic of swine flu that lasted over a 2 year period “took the summer off” (when vitamin D levels were higher) before restarting. There is a well known story of an English long term care facility in which one ward of the entire facility had no cases of influenza during a flu epidemic. The physician in charge of that ward had given all his patients a significant dose of vitamin D daily.
For the first time, as published in the May, 2010 issue of the American Journal of Clinical Nutrition, a rigorously designed randomized, double-blind, controlled clinical trial evaluated the effect of vitamin D on seasonal influenza A. Over 4 months children were given either 1200 units of vitamin D or placebo. Each case of influenza A was confirmed with influenza antigen testing with a nose/throat swab. 18 of 167 children given vitamin D compared to 31 of 167 children given placebo were diagnosed with the flu. This represents a reduction of 41.9%. The reduction was even more prominent in those children that previously weren’t taking any vitamin D supplements (most American children aren’t). It should be stressed that this study was double blind, so that the medical personnel diagnosing the flu and doing the laboratory flu studies did not know which children took the placebo and which children took the vitamin D.
A second result of the vitamin D supplements was an 83% reduction of asthma attacks in children with a diagnosis of asthma. Positive effects of vitamin D and asthma have been widely reported in research studies over the past 5 years.
It should be noted that 25-hydroxy vitamin D levels weren’t obtained. Previous studies have reported that 70% of American children have low levels of 25-hydroxyvitamin D (less than 32 ng.) Many of the 167 children were probably so low that the 1200 units of vitamin D didn’t give them ideal or even normal levels of vitamin D. So the 41.9% reduction is a very conservative figure of the percentage of influenza that could be prevented by achieving ideal 25-hydroxyvitamin D levels.
And finally, it should be also emhasized that you probably didn't hear about this study until today. I found out about it by chance on the day I am writing this. This emphasizes that unfortunately we can NOT rely on the press to keep us informed of critically important medical studies.