(Importantly, a small percentage of people get ill consuming even a small amount of Vitamin D supplement, as little as 3000 IU. And another small group of people cannot effectively absorb or convert Vitamin D supplements into serum (blood) Vitamin D. But most people can both consume and digest Vitamin D supplements in much higher doses.)
In February of 2009 a study found 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.”
PLoS One published a study that strongly suggests that raising the blood serum level of Vitamin D to over 38 ng/ml could result in a significant reduction in viral respiratory illnesses.
Serum 25-Hydroxyvitamin D and the Incidence of Acute Viral Respiratory Tract Infections in Healthy Adults
James R. Sabetta, Paolo DePetrillo, Ralph J. Cipriani, Joanne Smardin, Lillian A. Burns, Marie L. Landry Research Article, published 14 Jun 2010 doi:10.1371/journal.pone.0011088
“Concentrations of 38 ng/ml or more were associated with a significant (p<0.0001) two-fold reduction in the risk of developing acute respiratory tract infections and with a marked reduction in the percentages of days ill.
“Maintenance of a 25-hydroxyvitamin D serum concentration of 38 ng/ml or higher should significantly reduce the incidence of acute viral respiratory tract infections and the burden of illness caused thereby, at least during the fall and winter in temperate zones.
“The findings of the present study provide direction for and call for future interventional studies examining the efficacy of vitamin D supplementation in reducing the incidence and severity of specific viral infections, including influenza, in the general population and in subpopulations with lower 25-hydroxyvitamin D concentrations, such as pregnant women, dark skinned individuals, and the obese.”
There’s tons of info on vitamin D (and other stuff) here - http://www.naturalfamilyawareness.com/health/index.php/2011/11/15/benefits-of-vitamin-d-why-its-essential-to-health-the-best-food-sources/
Since I began taking D3 at 2000 iu per day, respiratory problems and sinus drainage have disappeared. I have not had a cold in three years.
Aside, The medical group where my Dr practices began selling D3 and other common supplements labeled in it’s own name. They are in effect competing with Walgreen and Walmart. They have determined that D3 and fish oil have benefits that should be made available easily and cheaply to their patients.