| An article published in the February 23, 2009 issue of the American Medical Association journal Archives of Internal Medicine revealed an association between lower levels of serum vitamin D and decreased resistance to upper respiratory tract infection (URTI), otherwise known as the common cold. Researchers at Massachusetts General Hospital, Children’s Hospital, Boston, and the University of Colorado analyzed data from 18,883 participants in the Third National Health and Nutrition Examination Survey (NHANES III) of U.S. participants aged 12 and older. Physical examinations following enrollment obtained blood samples and information including the occurrence of recent upper respiratory tract infections. Stored blood samples were analyzed for serum 25-hydroxyvitamin D levels. Nineteen percent of the participants reported having a recent cold. For those whose serum vitamin D levels were lower than 10 nanograms per milliliter, the incidence was 24 percent, for subjects whose levels were 10 to less than 30 ng/mL the incidence was 20 percent, and the rate dropped to 17 percent among those with levels of 30 ng/mL or higher. After adjustment for demographic and other characteristics, those whose vitamin D levels were lowest experienced a 36 greater risk of URTI, and those whose levels were 10 to less than 30 ng/mL experienced a 24 percent greater risk compared with participants whose levels were at least 30 ng/mL. The association was significantly stronger for those with asthma. The study is the largest and most nationally representative of its kind to date. “To our knowledge, this is the first population-based study to evaluate and demonstrate an association between serum 25-hydroxyvitamin D level and URTI,” the authors remark. "The findings of our study support an important role for vitamin D in prevention of common respiratory infections, such as colds and the flu," concluded lead author Adit Ginde, MD, MPH, of the University of Colorado Denver Division of Emergency Medicine. "Individuals with common lung diseases, such as asthma or emphysema, may be particularly susceptible to respiratory infections from vitamin D deficiency." "A respiratory infection in someone with otherwise healthy lungs usually causes a few days of relatively mild symptoms," explained senior author Carlos Camargo, MD, DrPH, of the Massachusetts General Hospital Department of Emergency Medicine. "But respiratory infections in individuals with an underlying lung disease can cause serious attacks of asthma or COPD that may require urgent office visits, emergency department visits or hospitalizations. So the impact of preventing infections in these patients could be very large." "We are planning clinical trials to test the effectiveness of vitamin D to boost immunity and fight respiratory infection, with a focus on individuals with asthma and COPD, as well as children and older adults – groups that are at higher risk for more severe illness," Dr Ginde added. "While it's too early to make any definitive recommendations, many Americans also need more vitamin D for its bone and general health benefits. Clinicians and laypeople should stay tuned as this exciting area of research continues to expand." | 
