Low vitamin D may raise respiratory infection risk

NEW YORK (Reuters Health) - There appears to be an association between low blood levels of vitamin D and the risk of acute respiratory tract infection, Finnish researchers report.

"In our study of 800 young Finnish men, we found that those with low vitamin D levels were more likely to contract respiratory infections than controls," lead investigator Dr. Ilkka Laaksi told Reuters Health.

Laaksi, of the University of Tampere, and colleagues measured vitamin D concentrations in 800 young military conscripts. The average 25-hydroxyvitamin D concentration was 80.2 nmol/L.

At 6 months, the 24 subjects with concentrations below 40 nmol/L had a median of 4 days absent from duty because of respiratory infection -- significantly greater than the 2 days seen in controls.

The researchers found a significant association between vitamin D levels and the amount of physical exercise before military service. They also found significantly lower vitamin D levels in subjects who smoked.

"In the future," suggested Laaksi, "consideration must be given to clinical trials of vitamin D supplementation to investigate whether it enhances immunity to microbial infections."

SOURCE: American Journal of Clinical Nutrition, September 2007.