|
|
|
|
We’re all aware of the hazards of too much sun. But the flipside to seeking shelter in the shade is a growing trend towards inadequate levels of Vitamin D, which the body produces when skin is exposed to sunlight.
Now, a February 2009 study by investigators from the University of Colorado's Denver School of Medicine, Massachusetts General Hospital and the Children’s Hospital in Boston suggests that Vitamin D may provide a boost in the battle with the common cold and flu. “On its own, the study does not mean that higher Vitamin D intake will guarantee that you don’t get an upper respiratory tract infection this winter,” said Andrew Shao (Ph.D.), Vice President, Scientific and Regulatory Affairs, for the Council for Responsible Nutrition in Washington. “But it is consistent with the relatively new body of evidence showing that Vitamin D plays a critical role in immune function.”
Published in the February 23, 2009, issue of the Archives of Internal Medicine, the report is the largest American study to examine the association between Vitamin D and respiratory infections. It showed that participants with the lowest levels Vitamin D in their blood reported suffering a significantly greater number of colds and flu. The risks were even higher for those with chronic respiratory disorders, such as asthma and emphysema, for whom a routine viral infection can lead to a hospital visit.
The researchers conducted a secondary analysis of the Third National Health and Nutrition Examination Survey, a probability survey of the United States’ population that was carried out from 1988 to 1994. They examined the association between blood levels of Vitamin D and the rate of recent upper respiratory tract infections among 18,883 study participants who were 12 years and older.
After adjusting their analysis for demographics and clinical factors — such as season, body mass index, smoking, asthma and chronic obstructive pulmonary disease — the scientists found that individuals with low blood levels of a Vitamin D marker (25-hydroxyvitamin D) were also more likely to report a recent upper respiratory tract infection. Specifically, the analysis found that the participants with less than 10 nanograms/milliliter (ng/ml) of the Vitamin D marker had a 36 percent higher risk of cold or flu when compared to participants whose blood levels were greater than 30 ng/ml.
Blood levels of Vitamin D, they conclude, are inversely associated with respiratory tract infections, which may be more pronounced for people with chronic respiratory diseases.
“The evidence supporting the benefits of Vitamin D continues to build,” concludes Shao. “The majority of North Americans fall short of getting adequate Vitamin D through diet alone. Given that Vitamin D is relatively low in most foods, and there are serious risks associated with excessive sun exposure, dietary supplements are an important alternative to achieving a sufficient intake.”
Update July 28, 2009: According to The Globe and Mail, the Public Health Agency of Canada is looking into Vitamin D as a new weapon in the fight against H1N1.
|
|
|