” Using an entirely different bag of tricks, vitamin D can stifle infections, a capability that was presaged nearly a century ago when doctors successfully treated tuberculosis with sun exposure. The strategy is now understood to stem from increased vitamin D, which has been shown to trigger cells to produce a handy protein fragment called LL-37 that kills the TB bacterium.
The vitamin appears to defend against viral infections, too. The annual winter flu season comes at a time when people garner little vitamin D from sunshine and blood levels fall. The timing may not be a coincidence, says Reinhold Vieth, a biochemist at the University of Toronto. Low vitamin D levels might offer the virus the edge it needs to gain a foothold in the population and spread from person to person.”
.... works for me
I also take 50mg of Zinc daily. if I get a slight cold it seems to prevent cold sores