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