@sg8627
I think many of us who get hit hard by some supplements like vitamin D is down to our immune systems.
For example vitamin D worked wonders for me until I took Tribulus. Tribulus messed me up further, it seems to have increased receptor density which now causes me to get an abnormal immune response to stimuli from stuff like vitamin D
I would love to take vitamin D daily because it helps with muscle gain and penal shrinkage for me but by day 5 I get widespread inflammation. I have tried lowish dose three times over last year and keeps happening roughly by day 5 which I then stop supplementing and last time I did get bad headache too after waking up from afternoon nap.
I have had one trip to an endocrinologist and a second one to same one coming up soon but after what I described to him he said I would need high dose hydrocortisone to combat it.
He didn’t say he would prescribe, he was talking about prescribing low dose for food sensitivities and adrenal fatigue so I asked him would that solve the inflammatory response to Vitamin D and he said no; I would need 3 to 4 times the dose.
For me anyway, my immune system is a big piece of the jigsaw and I suspect likewise for many others too