According to vitamin D researcher Michael Holick, immune cells have vitamin D receptors. When an infection is detected–such as influenza–the cells respond by activating vitamin D.
That partly explains the results of a study I mentioned last week. When researchers gave generous daily doses of vitamin D3 to school children during flu season, risk of flu dropped considerably compared to kids who received a placebo.
But if you’re a few decades past your school years, you’ll probably be interested in a 2007 a study I came across that underlines how important adequate D levels are for adults.
Researchers in Finland used blood tests to measure vitamin D levels in 800 men serving on a Finnish military base.
After following the men for six months during flu season, researchers found that subjects with the lowest D levels were far more likely to suffer acute respiratory infection.
The study also produced two other notable results:
1) Higher D levels were common in subjects who reported the most physical exercise before induction into military service
2) Lower D levels were common among subjects who smoked
I think I’ll send this one over to the researchers at the Institute of Medicine. They’re the ones who recently reported that most people aren’t D deficient and need little or no supplementation.
“Researchers see link between vitamin D, flu immunity” John Fauber, Journal Sentinel, 5/10/09, jsonline.com
“An association of serum vitamin D concentrations < 40 nmol/L with acute respiratory tract infection in young Finnish men” American Journal of Clinical Nutrition, Vol. 86, No. 3, September 2007, ajcn.org