Cytokine production wasn't something I was able to include, simply because I was trying to cover a lot of ground in 1200 words! I alluded to it in the discussion about the cascade of events that occur when Vitamin D binds to immune cells. Cytokine production is one of those events. Still, I'm not completely convinced that Vitamin D deficiency directly leads to a higher chance of dying due to cytokine production. It's another one of those areas where we have a correlation, and a plausible explanation for causation... but it's not straightforward. And yes, the lack of sunlight is one explanation for why we seem to have so much Vitamin D deficiency... then again, maybe we see so much because we are defining deficiency the wrong way. There are so many things to discuss, and hopefully I can get to all of them.