VITAMIN D toxicity is considered to exist when one has very high blood levels of VITAMIN D and calcium AND calcium deposits in soft tissues - Studies on this complex subject are much debated, and it is difficult to draw solid conclusions. To avoid toxicity, it would seem that VITAMIN D levels need to be in the "just right"range, neither too little, nor too much. Evidence also suggests VITAMIN D toxicity may result from a relative deficiency of vitamins A and K. Symptoms of VITAMIN D toxemia, such as excessive calcium levels, are not generally observed until CALCIDIOL levels reach ~150 ng/mL.
Koutkia P, et al, 2001.Note: Robert Heany reports toxicity at 250 nmol/ L, which is 100 ng / mL, produced from >10,000 IU D / day.
Overdose of VITAMIN D from the sun is prevented by two inbuilt mechanisms:
-Excess VITAMIN D produced in the skin by UV-B rays - is further converted to various inactive forms of VITAMIN D;
-Pigment melanin (i.e. a tan) - begins to accumulate in skin tissues after exposure to UV-A rays, which decreases VITAMIN D production.
