nutritional disorders
Vitamin D Toxicity
Physiology ofVitamin DToxicity
Vitamin Dhas 2 main forms: D2 (ergocalciferol) D3 (cholecalciferol): The naturally occurring form and the form used for low-dose supplementation Vitamin D3 is synthesized in skin by exposure to direct sunlight (ultraviolet B radiation) and obtained in the diet chiefly in fish liver oils and salt water fish (see table). In some countries, milk and other foods are fortified withvitamin D. Human breast milk is low invitamin D, containing an average of only 10% of the amount in fortified cow’s milk. Vitamin Dlevels may decrease with age because skin synthesis declines. Sunscreen use and dark skin pigmentation also reduce skin synthesis ofvitamin D. Vitamin Dis a prohormone with several active metabolites that act as hormones.Vitamin Dis metabolized by the liver to 25(OH)D (calcifediol, calcidiol, 25-hydroxycholecalciferol, or 25-hydroxyvitamin D), which is then converted by the kidneys to 1,25-dihydroxyvitamin D (1,25-dihydroxycholecalciferol,calcitriol, or activevitamin Dhormone). 25(OH)D, the major circulating form, has some metabolic activity, but 1,25-dihydroxyvitamin D is the most metabolically active. The conversion to 1,25-dihydroxyvitamin D is regulated by its own concentration,parathyroid hormone(PTH), and serum concentrations of calcium and phosphate. Vitamin Daffects many organ systems (see table), but mainly it increases calcium and phosphate absorption from the intestine and promotes normal bone formation and mineralization. and related analogs may be used to treat Psoriasis , (See also Overview of Vitamins .) 1.Autier P, Mullie P, Macacu A, et al: Effect ofvitamin Dsupplementation on non-skeletal disorders: A systematic review of meta-analyses and randomised trials.Lancet Diabetes Endocrinol5 (12):986–1004, 2017. doi: 10.1016/S2213-8587(17)30357-1 2.Manson JE, Cook NR, Lee IM, et al:Vitamin Dsupplements and prevention of cancer and cardiovascular disease.N Engl J Med380(1):33-44, 2019. doi: 10.1056/NEJMoa1809944 3.Cianferotti L, Bertoldo F, Bischoff-Ferrari HA, et al:Vitamin Dsupplementation in the prevention and management of major chronic diseases not related to mineral homeostasis in adults: research for evidence and a scientific statement from the European Society for Clinical and Economic aspects of Osteoporosis and Osteoarthritis (ESCEO).Endocrine56:245-261, 2017. doi:10.1007/s12020-017-1290-9 4.Okereke OI, Reynolds CF 3rd, Mischoulon D, et al: Effect of long-term vitamin D3 supplementation vs placebo on risk of depression or clinically relevant depressive symptoms and on change in mood scores: A randomized clinical trial.JAMA324(5):471-480, 2020. doi: 10.1001/jama.2020.10224 5.Barbarawi M, Kheiri B, Zayed Y, et al:Vitamin Dsupplementation and cardiovascular disease risks in more than 83,000 individuals in 21 randomized clinical trials: A meta-analysis [published correction appears inJAMA Cardiol2019 Nov 6].JAMA Cardiol4(8):765-776, 2019. doi: 10.1001/jamacardio.2019.1870 6.Yao P, Bennett D, Mafham M, et al:Vitamin Dand calcium for the prevention of fracture: A systematic review and meta-analysis.JAMA Netw Open2(12):e1917789, 2019. doi:10.1001/jamanetworkopen.2019.17789 7.Kong SH, Jang HN, Kim JH, et al: Effect ofvitamin Dsupplementation on risk of fractures and falls according to dosage and interval: a meta-analysis.Endocrinol Metab37:344-358, 2022. doi:10.3803/EnM.2021.1374 8.Ling Y, Xu F, Xia X, et al:Vitamin Dsupplementation reduces the risk of fall in thevitamin Ddeficient elderly: an updated meta-analysis.Clin Nutr40:5531-5537, 2021. doi:10.1016/j.clnu.2021.09.031 9.Appel LJ, Michos ED, Mitchell CM, et al: The effects of four doses ofvitamin Dsupplements on falls in older adults: a response-adaptive, randomized clinical trial.Ann Intern Med174:145-156, 2021. doi:10.7326/M20-3812 