Dear Editor,

Vitamin D deficiency is one of the most common nutritional diseases worldwide, this is particularly true in Iran due to the populations limited exposure to natural sunlight, especially in urban areas. Several concerns exist regarding vitamin D deficiency, including disorders of calcium homeostasis, cardiovascular diseases, autoimmune disorders, and some common cancers.1,2 Hence, due to the devastating effects of vitamin D deficiency, Iranian people have been strongly encouraged to take vitamin D supplements and vitamin D is administered freely in schools and health centers. Consequently, products containing vitamin D became a popular medication and supplementation in the community. Additional amounts of vitamin D are ingested from processed foodstuffs such as fortified edible oil and dairy products.3 The irrational administration and consumption of vitamin D has transformed it into a double-edged sword. There are several reports regarding vitamin D toxicity after long-term consumption of vitamin D inappropriately. The toxicity of vitamin D may last for long duration because it is a fat-soluble vitamin with a high accumulation rate in adipose tissue. Remarkably, the 25-hydroxyvitamin D level has been reported to be up to 500 ng/mL in some case reports, which demonstrate that the irrational usage of vitamin D could lead to severe toxicity.4,5 A case series study concluded that hypervitaminosis is the most important differential diagnosis of patients with hypercalcemia, particularly in endemically vitamin D deficient regions.6 The study warned physicians against prescribing vitamin D in high doses without careful monitoring.6 Vitamin D toxicity is accompanied by several serious problems. Early symptoms of toxicity include gastrointestinal disorders, bone pain, lethargy, severe headaches, arrhythmia, frequent urination, calcinosis, and nephrolithiasis.7 Therefore, it is necessary to employ effective strategies to correct this irrational pattern of vitamin D usage. The appropriate regimen of vitamin D should be prescribed based on age, associated risk factors, and 25-hydroxyvitamin D levels. The necessary education should also be provided to health care providers and the general public. In addition, high doses of vitamin D products should not be purchased from pharmacies without a vast medical or nutritional history. By employing these strategies, the toxicity of vitamin D can be diminished significantly and avoid any potential issues for the countries health system. This letter is the first published alarm for health professionals
in Iran.

references

1. 1. Ebrahimi M, Khashayar P, Keshtkar A, Etemad K, Dini M, Mohammadi Z, et al. Prevalence of vitamin D deficiency among Iranian adolescents. J Pediatr Endocrinol Metab 2014 Jul;27(7-8):595-602.
2. 2. Miroliaee AE, Salamzadeh J, Shokouhi S, Fatemi A, Ardehali SH, Hajiesmaeili MR, et al. Effect of vitamin D supplementation on procalcitonin as prognostic biomarker in patients with ventilator associated pneumonia complicated with vitamin D deficiency. Iran J Pharm Res 2017;16(3):1254-1263.
3. 3. Hovsepian S, Amini M, Aminorroaya A, Amini P, Iraj B. Prevalence of vitamin D deficiency among adult population of Isfahan City, Iran. J Health Popul Nutr 2011 Apr;29(2):149-155.
4. 4. Ziaie H, Razmjou S, Jomhouri R, Jenabi A. Vitamin D toxicity; stored and released from adipose tissue? Arch Iran Med 2016 Aug;19(8):597-600.
5. 5. Taylor PN, Davies JS. A review of the growing risk of vitamin D toxicity from inappropriate practice. Br J Clin Pharmacol 2018 Jun;84(6):1121-1127.
6. 6. Koul PA, Ahmad SH, Ahmad F, Jan RA, Shah SU, Khan UH. Vitamin D toxicity in adults: a case series from an area with endemic hypovitaminosis. Oman Med J 2011 May;26(3):201-204.
7. 7. Alshahrani F, Aljohani N. Vitamin D: deficiency, sufficiency and toxicity. Nutrients 2013 Sep;5(9):3605-3616.