https://jamanetwork.com/journals/jama/fullarticle/2748796 If read carefully, this study @Yaya refers to was done on healthy people.   "Meaning  Among healthy adults, supplementation with higher doses of vitamin D did not result in improved bone health; further research would be needed to determine whether it is harmful." "...311 community-dwelling healthy adults without osteoporosis, aged 55 to 70 years, with baseline levels of 25-hydroxyvitamin D (25[OH]D) of 30 to 125 nmol/L."   High dose Vitamin D doesn't have substantial benefits if your Vitamin D level is already normal. High dose Vitamin D is used to restore severely deficient Vitamin D levels to normal levels.  "...high-dose vitamin D therapy, as a useful tool to rapidly replete vitamin D status, may support immune function in the context of an acute or chronic infection" ...and... "Therefore, in the context of inflammation and conditions where anemia is prevalent, including chronic kidney disease, cardiovascular disease, and critical illness, high-dose vitamin D supplementation may be beneficial in rapidly repleting and maintaining 25(OH)D concentrations and may serve as a complement to other treatment regimens to improve anemia." "Among those who had insufficient 25(OH)D (<75nmol/L) at baseline, the High Dose group improved significantly and to a comparatively greater degree on the PRM." These quotes are from the articles I posted earlier.

My cardio did not hand me a study.  He just determined the dose for my size/weight. Here is one that is 4 days old:  https://www.healthline.com/nutrition/how-much-vitamin-d-is-too-much This is the D study: https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/vitamin-d-toxicity/faq-20058108 This is a boring video I'm watching on Celiac.    

Can you link the 2019 JAMA study? When you say "massive doses of D" how large are you talking about? 

Thank you.  I'll run it by him on my next visit.