Biohacking has come more into the public domain with the publicity around Bryan Johnson's blueprint . Bryan Johnson is someone who is a tech entrepreneur who sold one of his businesses a few years ago and has since being trying to improve his health. This has been described in the media as him spending about USD 2 million a year with try to get his body to be the equivalent of an 18 year olds. However, it is probably best to read his website (that I have linked to) to see what he describes this as. There are quite a lot of people who are doing similar things, but not necessarily spending as much or promoting what they are doing to the same extent. His website provides quite a bit of information, but sadly at the moment it is not as useful as it could be as he does not always link to the relevant research papers or specify the units of the measurements he quotes. Hopefully that will be fixed over time. Dr Michael Lustgarten is similar to Bryan Johnson in that he publicises
We know Vitamin D exists. We know that people suffer if they don't have enough of it. However, it raises an interesting question as to why we evolved to create a vitamin in the summer which gets stored and then gradually fades away during the winter. I have an idea. Historically food was more plentiful in the summer and less available in the winter. The genes that rely on vitamin D don't function without it. Hence the body requires less energy. There are a number of things which operate to adjust metabolism to fit food availability. I think Vitamin D evolved to provide an annual metabolic cycle so things which could wait which required energy did not operate. That gives an idea as to what functions we would expect to depend on vitamin D. It would be those functions which are useful, but not essential all year round.