| Research suggests that seasonal vitamin D | | | | anti-microbial substances in immune cells, helping to |
| deficiency could be linked to flu outbreaks in North | | | | halt the replication of viruses in the body. It is also |
| America and other temperate areas. | | | | known to help modulate the body's response to |
| Flu is largely seasonal in temperate areas, | | | | respiratory viruses, preventing the overproduction |
| appearing and spreading rapidly during the fall and | | | | of substances that can lead to dangerous and |
| winter, subsiding through the spring and summer | | | | even fatal inflammation and fluid buildup in the |
| months, and sometimes reemerging the following | | | | lungs. |
| autumn. Records show that flu outbreaks occur | | | | Though there is disagreement on vitamin D's role |
| when solar radiation is at its lowest. In temperate | | | | as a flu fighter and the concept has yet to be |
| climates flu virtually disappears during the summer | | | | substantiated by large-scale clinical tests, |
| months, while in tropical climates the seasonality is | | | | observational data and laboratory research |
| much less pronounced. | | | | support the idea that low levels of the vitamin are |
| Researchers say the seasonal nature of flu | | | | indeed implicated in flu outbreaks. |
| outbreaks could possibly be linked to levels of | | | | Among the most recent research projects to |
| Vitamin D, recently discovered to play an | | | | support the connection was a February, 2009 |
| important role in immune function. Exposure to | | | | study published in the Archives of Internal |
| the sun triggers the body to produce the vitamin, | | | | Medicine, which reported a link between upper |
| which is present in only a few foods. Lack of sun | | | | respiratory infections and low vitamin D blood |
| exposure during the fall and winter may result in | | | | levels. The study, which focused on 19,000 |
| low levels of D vitamin, and a growing body of | | | | patients, showed that those with vitamin D |
| research points to deficiency of the vitamin as an | | | | deficiency were 55% more likely to have upper |
| important part of susceptibility to the flu. | | | | respiratory infections. |
| D vitamin is known to stimulate the production of | | | | |