Vitamin D supplementation can prevent influenza

Tl;dr: You should probably consider taking Vitamin D supplements to prevent influenza and reduce the likelihood you develop complications from influenza. They are super cheap: like $0.10 daily.

Recently I learned that taking Vitamin D can reduce both the infection rates of and the impact of influenza.

It's believed that the way this works is by dampening the body's immune response to influenza. Our immune response is what actually causes the pneumonia and other respiratory illnesses which can be the true cause of influenza mortality.

One interesting study found that those living in San Antonio, TX during the 1918 influenza crisis were four times less likely to die than those living in New London, CT. People who lived in New London had the lowest amount of UVB radiation (i.e. sun exposure, one of two ways we can get Vitamin D); those living in San Antonio had the greatest UVB exposure.

Another recent study found that schoolchildren who received 1200 IU/day had 42% lower influenza rates.

Increased sun exposure during the summer is also a possible explanation of lower influenza rates then.

Thankfully, I have been taking Vitamin D since Christmas time when I learned that David Sinclair takes Vitamin D. Since I don't get that much sun exposure living in a relatively cool climate I thought I could stand some supplemental, literally, Vitamin D.

Vitamin D supplements are trivially expensive on Amazon (5-10 cents/day).

There seem to be other positive health effects associated with higher Vitamin D levels as mentioned by David Sinclair on Twitter.

One thing I wondered was whether or not I am actually deficient in Vitamin D. Only one of the past four blood tests I've done with my health insurance provider seems to have tested for it, so hopefully others have better data as to whether or not they are deficient. My test result from 18 months ago was 36 ng/mL, which is at the low end of the "standard" range of 20-79 ng/mL.

I found the following excerpt that states that the "efficient" level is 30-80 ng/mL, so it seems that I was at the low end of the range, as of 18 months ago (during the summer).

"Guidance serum concentration of 25(OH)D, which indicates an efficient level of vitamin D in the organism, is 30–80 ng/mL (ca. 75–200 nM/L). A severe vitamin D deficiency is reflected in serum concentrations below 10 ng/mL"

If you know your Vitamin D level it would be interesting to see the correlation between it and your latitude and outdoor activity levels.

I had to remove all of my sources/links FYI.

Hope this helps someone!