Vitamin D May Help Protect Against the Flu

Maintaining high levels of vitamin D this winter may enhance protection against the H1N1 flu, according to an analysis of deaths and complications from the 1918-1919 flu pandemic.

William B. Grant, PhD, of the Sunlight, Nutrition and Health Research Center in San Francisco, and Edward Giovannucci, MD, ScD, of the Harvard University School of Public Health, investigated the number of deaths and incidence of pneumonia associated with the deadly flu 90 years ago.

They found that the fewest deaths and cases of pneumonia occurred in two southern American cities included in the data analysis. Residents of those cities would have had the highest sunlight exposure and vitamin D production during the previous summer. The greatest number of deaths and pneumonia cases occurred in northern cities – those with less sun exposure.
Grant and Giovannucci noted that the fatal complications of flu result in part from a secondary bacterial infection, such as pneumonia.

Vitamin D is needed for the body’s production of cathelicidin, an antibacterial peptide that has been shown to fight tuberculosis and septicemia. Vitamin D also protects against endotoxins, which are released by bacteria when they are destroyed.

Reference: Grant WB, 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;1:1-5.