I'm currently learning a tonne of interesting stuff from
Chris Masterjohn Phd. In one of his masterclasses on nutrition and immunity, he talks about the importance of not only Vitamin D but also Vitamin A in immune function.
"Vitamins A and D are used up for differentiation of immune cells during infections; without them, T cells are suppressed."
Taken from
Nanna1's Immune Suppresion/Immune Tolerance model of POIS:
Since, most POISers recover from POIS in the 5 to 7-day range. The time kinetics of NK, T, B cells seems to suggest that, in the absence of an immunocompetent NK response, POIS recovery is correlated with the time-dependent expansion of non-memory CD8+ T cells.
This time-dependent increase in CD8 T cells occurs during sleep (How Sleep Fights Infection: Snoozing Makes Killer Immune Cells More Sticky). So, the sooner sleep occurs following orgasm, the sooner CD8 T cells can start replacing the function of NK cells in the immune response. Moreover, sleep deprivation has been shown to suppress NK cells in humans (Ref1, Ref2, Ref3). So good sleep is vital for immune function and recovery from POIS.
Now I'm not a scientist, but connecting these two bits of information on T cells: Both Vitamin A and D are important for POIS recovery, as without them, T cells which POISers rely on according to Nanna1's theory, may be repressed.
Other quotes from his masterclass:
"Every “immune event” taxes vitamins A and D."
"Vitamin A and D are depleted during Covid."