The risk of children suffering from flu can be halved if they take vitamin D, doctors in Japan have found. The finding has implications for flu epidemics since vitamin D, which is naturally produced by the human body when exposed to direct sunlight, has no significant side effects, costs little and can be several times more effective than anti-viral drugs or vaccine. …
Anti-virals are also too expensive, and possibly too toxic, to be given to the population as a whole whereas vitamin D has additional benefits. The sunshine vitamin not only prevents bone fractures but is also believed to reduce risks of cancer, heart disease, diabetes and other illness, including various bacterial as well as viral infections.
The Japanese finding supports a theory that low blood levels of the sunshine vitamin occurring in winter explain why flu epidemics generally peak between December and March.
Vitamin D activates the innate immune system, enabling the body to produce several proteins such as defensin and cathelicidin which trigger cell activity and disable viruses.