The Easiest Way to Prevent Colds and Flu

Collectively, we cough, sniffle and sneeze our way through one billion colds a year, spending 1.5 billion dollars for doctor visits and 2 billion dollars on non-prescription cough and cold treatments. Fortunately, few people die of a cold. But you can't say that about the flu.

The influenza virus hospitalizes more than 200,000 Americans a year and kills 36,000, many of them over 65. (And flu shots are no guarantee. From 2007 to 2008, the shot was only 44 percent effective in stopping the flu.)

Is there any way to make yourself less vulnerable to these two infections?

Yes, says a study published on June 14 in the open access online medical journal Plos One. Make absolutely certain you have higher-than-normal blood levels of vitamin D.

Here's what you need to know about the study and its practical application.

The study was led by James R. Sabetta, MD, in the Department of Medicine at Yale University School of Medicine and the Section of Infectious Diseases at Greenwich Hospital in Greenwich, Connecticut. He and his colleagues observed the obvious: rates of "acute respiratory tract infections" (colds and flu) rise in the fall and winter. But why? Could the seasonal drop in blood levels of vitamin D -- a hormone-like nutrient produced most abundantly in the body when the skin is exposed to the strong, direct sunlight of summer -- explain the phenomena?

To find out, the researchers took monthly measurements of the blood levels of vitamin D (25-hydroxyvitamin D) in 195 healthy adults. The measurements started the third week in September and continued for the next four to five months. At the same time, the study participants were asked to report any acute respiratory tract infections. The results were, well, decisive.