Common ColdInfectionVitamins

Vitamin D and respiratory infection risk

Circumstantial evidence implicates the wintertime deficiency of vitamin D from too little sunlight, with an increase in colds and flu.

Researchers from Denver, Colorado and Boston, Massachusetts looked for an association.

First, the details.

  • Results from the Third National Health and Nutrition Examination Survey (NHANES III) were reviewed.
  • The survey included 18,883 participants.
  • Blood levels of 25-hydroxyvitamin D (25OHD) — the best measure of vitamin D status — were compared with the incidence of upper respiratory tract infections.
  • Confounding factors (season, body mass index, smoking history, asthma, and chronic obstructive pulmonary disease) were considered in the review.

And, the results.

  • Those with the lowest vitamin D blood levels — less than 10 ng per milliliter of blood — were about 40% more likely to report a recent respiratory infection vs those with vitamin D levels of 30 or higher.
  • The association was present in all seasons.
  • The association was stronger in those with a history of asthma or chronic obstructive pulmonary disease (COPD), including emphysema.
    • Asthma patients with the lowest vitamin D levels were 5 times more likely to have had a recent respiratory infection.
    • Among COPD patients, respiratory infections were twice as common among those with vitamin D deficiency.

The bottom line?
The authors concluded that those with the lowest blood levels of vitamin D were at greatest risk of getting a respiratory tract infection.

Next step? Another study where participants are followed in real time, say the authors.

3/1/09 23:09 JR

Hi, I’m JR

John Russo, Jr., PharmD, is president of The MedCom Resource, Inc. Previously, he was senior vice president of medical communications at, a complementary and alternative medicine website.