Study Shows Vitamin D May Have a Role to Play in Preventing Cold and Flu infections

March 12, 2009

A new study adds to mounting evidence that Vitamin D may be a real cold fighter. The study, the largest to date on the link between vitamin D and common respiratory infections, shows that people with the lowest levels of vitamin D have significantly more cases of cold and flu infection than those with higher levels. According to A. Ginde, MD, MPH, of the University of Colorado, in Denver “The findings of our study support an important role for vitamin D in prevention of common respiratory infections, such as colds and the flu,” in a news release. “Individuals with common lung diseases, such as asthma or emphysema, may be particularly susceptible to respiratory infections from vitamin D deficiency.”  

Circumstantial evidence originally pointed at the notion that wintertime low levels of vitamin D were related to the seasonal increases in colds and flu, some smaller studies have also pointed to a link between low vitamin D level and a higher risk of respiratory infections. In this study the researchers analyzed information on vitamin D levels and respiratory infections in a population of nearly 19,000 adults and adolescents who participated in the Third National Health and Nutrition Examination Survey (NHANES III) from October 1988 to October 1994.  

The results showed those with the lowest vitamin D levels (less than 10 nanograms per milliliter of blood) were 36% more likely to report having a recent upper respiratory tract infection than those with higher levels (30 ng/mL or higher). This association persisted during all four seasons and was even stronger among those with a history of asthma or chronic obstructive pulmonary disease (COPD). For example, people with asthma with the lowest vitamin D levels were five times more likely to have had a recent respiratory infection. Among those with COPD, recent respiratory infections were twice as common among those with lowest vitamin D levels. The study results are published in the February 23rd, 2009 issue of the journal Archives of Internal Medicine..