I mean, obviously we need the sun to live. But what happens when we don't get enough of it? Often, this leads to vitamin D deficiency. This can lead to a whole range of issues. One of these is actually incredibly scary(so get some sun!). A lack of vitamin D can lead to an increased risk of sepsis, according to one paper from 2017 by Zeljic et.al. which outlines the way this happens. Sepsis is a phenomenon that often occurs in hospitalized patients when the body begins to become inflamed due to a foreign virus or organism which can be fatal. Vitamin D receptors are a major key in many biological functions, including inflammatory responses, which is how sepsis occurs, as well as maintaining homeostasis during sepsis.
Zeljic et.al. 2017 details that genetic predispositions to sepsis have been found but this experiment looks into vitamin D receptor(VDR) deformations may affect the likelihood of sepsis. It was found that homozygous CC genotypes had an increased risk of sepsis in comparison to a TT genotype of VDR. This is incredibly important because, while we try our best to get into the sun and get vitamin D in as many ways as possible, some people may just be destined to have a deficiency(a little morbid, I know). However, this can lead to more research questions about how we can use dna sequencing and gene splicing to possibly eradicate this issue in the future.
Link to paper: http://onlinelibrary.wiley.com/doi/10.1111/iji.12318/full