Diminished vitamin D levels may be linked to the spread of the flu. Research found that nonpandemic influenzas occur primarily in temperate regions and in winter when the skin’s vitamin D formation due to sun exposure is low. Influenza seasonality is seldom observed in tropical regions.
Although an initial pandemic can start in any season, secondary waves often occur in autumn or winter, and can be more serious. The increased lethality of secondary winter waves can also be explained by decreased vitamin D levels.
Vitamin D levels are at their highest approximately one month after the flu season (near midsummer). At latitudes above 37 degrees, UVB exposure is greatly reduced from November through February, meaning that vitamin D production in the skin is minimal. Because of the role vitamin D plays in the immune system, a reduction in this important compound is associated with a decline in immune function, leading to decreased resistance against influenza and other pathogens.
Study: “The seasonality of pandemic and non-pandemic influenzas: the roles of solar radiation and vitamin D” by Asta Juzenienea et. al in International Journal of Infectious Diseases, Volume 14, Issue 12, December 2010, Pages e1099–e1105. https://www.sciencedirect.com/science/article/pii/S1201971210024975
Note: In the winter of 2013, flu shots were found to be significantly less effective, especially in the elderly. Therefore, any proven and non-harmful method of reducing your chances of getting the flu should be considered. In wintertime, it is difficult to get sufficient vitamin D from sun exposure. If the diet does not contain enough Vitamin D, supplementation may be required.
Low Vitamin D & Asthma
Not surprisingly, low levels of vitamin D appear to have consequences for other respiratory conditions such as asthma and scientists have found a link between the two. African American children in Washington DC who have asthma are much more likely to have very low vitamin D levels than healthy African American children in the same region.
Researchers: Children’s National Medical Center.
Editor’s note: This study supports recent research showing vitamin D plays a greater role in the body than just keeping bones healthy, including depression, autoimmune disorders, cancer prevention and now asthma.
Low Vitamin D & Other Conditions