# 2831
Even without the possibility of an influenza pandemic looming sometime in the future, colds and flu's exact a heavy toll in terms of lives, lost productivity, and misery every year.
Influenza-like illnesses(ILI's) lead to thousands of deaths each year in the United States, and hundreds of thousands of deaths worldwide.
Vaccines are our best protection against seasonal influenza viruses, but they don't offer complete protection.
And given the wide variety of respiratory viruses that circulate each year that aren't covered by the vaccine, it would certainly be desirable if there were something simple you could do to help protect yourself against them.
Over the past couple of days the media has been reporting on a study that suggests that Vitamin D might offer some sort of protection against respiratory viruses.
Too Little Vitamin D May Mean More Colds and Flu U.S. News & World Report
Vitamin D Levels Linked to Respiratory Tract Infections Lower ... Modern Medicine
This is not the first time that Vitamin D has been linked to preventing colds and flu, although no conclusive studies have been published.
The anecdotal evidence, however, is interesting.
Today's study, which appears in the February 23rd edition of the Archives of Internal Medicine, shows an inverse relationship between a person's level of serum 25-hydroxyvitamin D and a recent bout with a cold or flu.
Those who had recently experienced an ILI or other respiratory illness, were more likely to have lower than normal Vitamin D levels.
The median serum level of 25-hydroxyvitamin D, among more than 18,000 people tested, was 29 ng/ml.
Those with a serum level below 10 ng/ml (considered very low), were 40% more likely to have had a recent respiratory illness than those with a serum level above 30 ng/ml.
The link between Vitamin D levels and the risk for respiratory infections was stronger in those with asthma or COPD.
Certainly not conclusive evidence, but intriguing nonetheless.
The problem with this study is that it looks backwards, not forwards. Researchers can't know, with certainty, that the subjects who reported recent infections had low vitamin D levels before they got sick.
Since the half-life of Vitamin D in the body is normally about 15 days, researchers are inclined to believe that the lower levels detected were probably present prior to infection.
But it is also possible that having a cold or flu could somehow lower a person's Vitamin D level, if for no other reason than they are probably inside more, and exposed less to the UV rays of the sun.
In other words, the jury is still out.
The desirable level of Vitamin D is a subject of much debate, although the NIH lists levels below 20 ng/ml as being inadequate for good health.
Some researchers advocate a level ≥30 ng/ml, although a recent government-sponsored expert panel concluded that insufficient data was available to support these higher levels.
So, until clinical trials are conducted, the value of taking extra Vitamin D to help ward off colds and flu's remains unproven.
But we do know that many people have inadequate levels of Vitamin D in their systems, particularly during the winter months.
So while we don't know if a little extra vitamin D will help protect you from a cold or flu - like eating chicken soup when you have a cold - if you're considering trying it . . . it probably wouldn't hurt.
