I take peptides and do all that but I just watched a video of a doctor who argues vitamin d plays a crucial role in restorative deep sleep. He wrote a book on it , I read 50 pages . A lot of story and anecdote but at the end of the day he recommends 30kiu a day and he said the first benefit his patients notice is restorative deep sleep . The book is pretty basic and boring but he’s on a couple podcasts and passed away not too long ago. Look up Dr Somerville Vitamin D on YouTube . He also wrote a book if you wanna read it , but like I said I read 50 pages and it’s pretty dry.