10. Cannel, MD, John Jacob, "The Truth About Vitamin D Toxicity," http:///. Published September 4, 2003. Accessed May 24, 2006. 11. Rosenfeld, Louis, "Vitamine - vitamin. The early years of discovery," Clinical Chemistry, Vol. 43 No. 4 (1997) 680-685. 12. DeLuca, Hector F., "Historical Overview," in Feldman et al., eds., Vitamin D, San Diego: Academic Press (1997) 3-11. 13. Dobs, et al., "Effects of pravastatin, a new HMG-CoA reductase inhibitor, on vitamin D synthesis in man," Metabolism, Vol. 40 No. 5 (1991) 524-8. 14. Folkers, et al., "Lovastatin decreases coenzyme Q levels in humans," Proc Natl Acad Sci USA Vol. 87 No. 22 (1990) 8931-4. 15. Heaney, Robert P., "The Vitamin D requirement in health and disease," Journal of Steroid Biochemistry & Molecular Biology, 97 (2005)13-19. 16. Cannel, MD, John Jacob, "The Vitamin D Newsletter: April 2006 -- Dr. Cannell Answers Readers' Questions," Vitamin D Council: http:///PDFs/April2006-. Published April 1, 2006. Accessed May 25, 2006. 17. Masterjohn, Chris, "Vitamin A on Trial: Does Vitamin A Cause Osteoporosis?" Wise Traditions , Spring 2006.
Despite the importance of the sun for vitamin D synthesis, it is prudent to limit exposure of skin to sunlight [ 19 ] and UV radiation from tanning beds [ 21 ]. UV radiation is a carcinogen responsible for most of the estimated million skin cancers and the 8,000 deaths due to metastatic melanoma that occur annually in the United States [ 19 ]. Lifetime cumulative UV damage to skin is also largely responsible for some age-associated dryness and other cosmetic changes. The American Academy of Dermatology advises that photoprotective measures be taken, including the use of sunscreen, whenever one is exposed to the sun [ 22 ]. Assessment of vitamin D requirements cannot address the level of sun exposure because of these public health concerns about skin cancer, and there are no studies to determine whether UVB-induced synthesis of vitamin D can occur without increased risk of skin cancer [ 1 ].
The main symptoms of vitamin D overdose which are those of hypercalcemia including anorexia , nausea, and vomiting. These may be followed by polyuria , polydipsia , weakness, insomnia, nervousness, pruritus and ultimately renal failure . Furthermore, proteinuria , urinary casts , azotemia , and metastatic calcification (especially in the kidneys) may develop.  Other symptoms of vitamin D toxicity include mental retardation in young children, abnormal bone growth and formation, diarrhea, irritability, weight loss, and severe depression.