Full-text evidence summary


 If one develops influenza, taking extra vitamin D can strengthen the body’s innate immune system and reduce the symptoms of influenza and risk of developing bacterial pneumonia.  

There are no published studies of treating those with influenza with vitamin D; however, it is reasonable to expect that if one who develops influenza takes a large dose of vitamin D3 (e.g., 10,000 IU/day), sufficient amounts of cathelicidin and defensins will be induced within a couple of days, strengthening the innate immune system’s ability to fight both influenza and pneumonia, the primary risk for death following influenza infection.  However, there are no clinical trials to support this suggestion at present.  

In responding to the viral infection, the body’s innate immune system generates proinflammatory cytokines, which have the effect of disrupting the epithelial lining of the lung.  This event permits the ever-present bacteria to lead to pneumonia, with death, if it is the result, likely to occur about ten days after the influenza infection1.  

In an ecological study of the case-fatality rate in twelve U.S. communities during the 1918-19 epidemic influenza reported in Britten1 [1932], it was shown that indices for summertime and wintertime solar UVB explained 46% and 42% of the variance, respectively2

Page last edited: 17 May 2011


  1. Britten, R. H. The incidence of epidemic influenza, 1918-19. Pub Health Rep. 1932; 47303-39.
  2. Grant, W. B. Giovannucci, E. The possible roles of solar ultraviolet-B radiation and vitamin D in reducing case-fatality rates from the 1918-1919 influenza pandemic in the United States. Dermato-Endocrinology. 2009; 1 (4): 215-219.