Low Vitamin D levels increases risk of common cold

The largest study of its kind to date shows that vitamin D can prevent the common cold or the flu.

The finding is based on an assessment of vitamin D levels, nutritional habits and respiratory infection rates among nearly 19,000 American men and women.

Study author Dr. Adit Ginde, an assistant professor of surgery in the division of emergency medicine at the University of Colorado Denver School of Medicine said "our study provides support that lower levels of vitamin D are associated with an increased risk for respiratory infections, such as the common cold and the flu. And people who have pre-existing respiratory disease -- like asthma an emphysema -- appear to be at an increased risk for this association."

Ginde's team, from Harvard Medical School and Children's Hospital Boston, reports its findings in the Feb. 23 issue of the Archives of Internal Medicine.

Participants were aged 12 and up -- with an average age of 38 -- and three-quarters were white. All completed nutritional and health surveys and had physical examinations. Blood samples were taken to measure levels of 25-hydroxyvitamin D, considered to be the optimal measure of vitamin D status.

The researchers found that those with less than 10 nanograms of vitamin D per milliliter of blood, considered low, were nearly 40 percent more likely to have had a respiratory infection than those with vitamin D levels of 30 ng or higher. The finding was consistent across all races and ages.

In particular, people who had a history of asthma or some form of chronic obstructive pulmonary disease (COPD) were even more likely to suffer from vitamin D deficiencies.

Asthma patients with the lowest vitamin D levels had five times the risk for respiratory infection, and vitamin D-deficient COPD patients had twice the risk.

Bonnie - what is most encouraging is that they used a young subject base that were not already sick or had preexisting diseases.