Low Vitamin D Levels Linked to Colds
Study Shows Vitamin D May Have a Role to Play in Preventing Colds and Flu
Feb. 23, 2009 -- A walk in the sun may be better than popping a vitamin C
tablet for boosting your chances of preventing the common cold or flu.
A new study adds to mounting evidence that vitamin C may have been stealing
the spotlight all these years from the real cold fighter, vitamin D.
The study, the largest to date on the link between vitamin D and common
respiratory infections, shows that people with the lowest vitamin D levels
report having significantly more cases of cold and flu than those with higher
levels. Vitamin D is produced by the body in response to sunlight and is also
found in fortified foods such as milk.
Researchers say that although vitamin C has been used for the prevention of
common colds and other respiratory infections for decades, there is little
scientific evidence to support its effectiveness. However, several recent
studies have suggested that vitamin D, better known for its role in building
strong bones, may also play a critical role in immune system function.
"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 researcher Adit Ginde, MD, MPH, of the University of Colorado, Denver,
Division of Emergency Medicine, in a news release. "Individuals with common
lung diseases, such as asthma or emphysema, may be particularly
susceptible to respiratory infections from vitamin D deficiency."
Vitamin D vs. Colds
Although circumstantial evidence has implicated wintertime low levels of
vitamin D to the seasonal increases in colds and flu, some smaller studies have
also hinted at a link between low vitamin D level and a higher risk of
In this study, published in the Archives of Internal Medicine,
researchers analyzed information on vitamin D levels and respiratory infections
from nearly 19,000 adults and adolescents who participated in the Third
National Health and Nutrition Examination Survey (NHANES III) from October 1988
to October 1994.
The results showed those with the lowest vitamin D levels (less than 10
nanograms per milliliter of blood) were 36% more likely to report having a
recent upper respiratory tract infection than those with higher levels (30
ng/mL or higher).
This association persisted during all four seasons and was even stronger
among those with a history or asthma or chronic obstructive pulmonary disease
For example, people with asthma with the lowest vitamin D levels were five
times more likely to have had a recent respiratory infection. Among those with
COPD, recent respiratory infections were twice as common among those with
lowest vitamin D levels.
"We are planning clinical trials to test the effectiveness of vitamin D
to boost immunity and fight respiratory infection, with a focus on individuals
with asthma and COPD, as well as children and older adults -- groups that are
at higher risk for more severe illness," Ginde says. "While it's too
early to make any definitive recommendations, many Americans also need more
vitamin D for its bone and general health benefits."