"The findings of our study support an important role for vitamin D in prevention of common respiratory infections, such as colds and the flu," says Adit Ginde, MD, MPH, UC Denver Division of Emergency Medicine and lead author of the study in a recent news release. "Individuals with common lung diseases, such as asthma or emphysema, may be particularly susceptible to respiratory infections from vitamin D deficiency."
Information from approximately 19,000 subjects who participated in the Third National Health and Nutrition Examination Survey (NHANES III) was analyzed for this study.
"A respiratory infection in someone with otherwise healthy lungs usually causes a few days of relatively mild symptoms," explains Carlos Camargo, MD, DrPH, MGH Department of Emergency Medicine and senior author of the study. "But respiratory infections in individuals with an underlying lung disease can cause serious attacks of asthma or COPD that may require urgent office visits, emergency department visits or hospitalizations. So the impact of preventing infections in these patients could be very large."
Compared with individuals with serum 25(OH)D levels of 30 ng/mL or more, those with levels less than 10 ng/mL or 10 to less than 30 ng/mL had 55% and 27% higher odds of recent URTI, respectively (Table 2, model 1). In further stratification of the group with 25(OH)D levels of 30 ng/mL or more, those with levels of 30 to less than 40 ng/mL had similar odds of recent URTI compared with those with levels of 40 ng/mL or more (OR, 0.99; 95% CI, 0.81-1.21). After adjusting for season, lower serum 25(OH)D levels were still associated with a significantly higher URTI (Table 2, model 2). Indeed, the 25(OH)D-URTI association was consistent across all seasons.
The authors stress that the study's results need to be confirmed in clinical trials before vitamin D can be recommended to prevent colds and flu.
...randomized controlled trials are valuable for determining the causal nature of an observed association. Reverse causation (ie, lower serum 25[OH]D levels due to recent URTI and, thus, decreased outdoor activity) seems unlikely because the half-life of serum 25(OH)D is 2 to 3 weeks11 and URTIs last only 3 to 4 days,3 but it may affect the enhanced vitamin D–URTI association in participants with asthma and COPD owing to longer symptom duration in those individuals....Randomized controlled trials are warranted to explore the direct effect of vitamin D supplementation and to establish optimal levels of serum 25(OH)D in the prevention of RTI.
Previous articles about which I've blogged, Vitamin D and the thyroid gland... and Vitamin D: "Normal" isn't normal anymore support greater daily intake of Vitamin D.
To read more:
- Assay Variation Confounds the Diagnosis of Hypovitaminosis D: A Call for Standardization
- Assessment of dietary vitamin D requirements during pregnancy and lactation
- Circulating Vitamin D3 and 25-hydroxyvitamin D in Humans: An Important Tool to Define
Adit A. Ginde, MD, MPH; Jonathan M. Mansbach, MD; Carlos A. Camargo Jr, MD, DrPH (2009). Association Between Serum 25-Hydroxyvitamin D Level and Upper Respiratory Tract Infection in the Third National Health and Nutrition Examination Survey Archives of Internal Medicine, 169(4)