In April 2005, an influenza epidemic started sweeping through the maximum-security hospital for the criminally insane where Dr. John Cannell worked.
As the epidemic progressed, he noticed something unusual: although wards all around his became infected, no patients on his ward became ill, despite intermingling of both patients and nurses.
The only difference was that all of the patients on Dr. Cannell's ward had been taking 2,000 units of vitamin D every day for several months or longer.
Shortly after the epidemic, a paper in the journal Nature showed that vitamin D was a potent antibiotic, working by increasing the body's production of proteins called antimicrobial peptides. Antimicrobial peptides destroy the cell walls of bacteria, fungi, and viruses, including the influenza virus.
Dr. Cannell posits that this explains such matters as:
- Why the flu predictably occurs in the months following the winter solstice, when vitamin D levels are at their lowest
- Why influenza is more common in the tropics during the rainy season
- Why children exposed to sunlight are less likely to get colds
- Why cod liver oil (which contains vitamin D) reduces the incidence of viral respiratory infections
- Why the elderly who live in countries with high vitamin D consumption, like Norway, are less likely to die in the winter
Epidemic influenza kills roughly a million people every year worldwide, usually by causing pneumonia.