Vitamin D Against Viruses

A study of 200 adults during last winter’s flu season indicates that vitamin D may play an important role in helping ward off upper respiratory tract viral infections. In this double-blind research, neither subjects nor investigators knew what the vitamin D levels were until the end of the study. Blood was drawn every month to determine 25-hydroxy vitamin D.
Participants were asked to keep a diary of their symptoms such as sniffles, cough, stuffy nose, sore throat and fever. Only about 17 percent of those with the highest levels of vitamin D, over 38 ng/ml, came down with a viral infection. If they did catch a cold or flu, they weren’t sick for long. Nearly half of those with lower levels of vitamin D caught a viral infection. The investigators speculate that reduced vitamin D levels in the winter may explain why colds and flu are so seasonal.
[PloS ONE, June 15, 2010]