No-one should ever even discuss Vitamin D toxicity, without fully internalizing this excellent lecture from Dr. Reinhold Vieth, or being fully cognizant of the details independently. Period.
I'll say it again, either populate the field with people of this quality, or get some good systemic, integrative problem-solvers in there.
Note: Posted this based on sheer instinct before watching fully, -completed now. There is a profundity in this lecture and the closing Q&A that is dramatic. Sadly, as Dr. Reinhold himself states during the talk, the analysis of the numbers and dynamics is really an engineering problem rather than a 1st order Kinetics / Enzmatic understanding issue, his quote from 39m30s: "the concepts are ....more understood by Engineers, than Biochemists and Nutritionists". Quite.