title: Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety.
abstract: For adults, the 5-microg (200 IU) vitamin D recommended dietary allowance may prevent osteomalacia in the absence of sunlight, but more is needed to help prevent osteoporosis and secondary hyperparathyroidism. Other benefits of vitamin D supplementation are implicated epidemiologically: prevention of some cancers, osteoarthritis progression, multiple sclerosis, and hypertension. Total-body sun exposure easily provides the equivalent of 250 microg (10000 IU) vitamin D/d, suggesting that this is a physiologic limit. Sailors in US submarines are deprived of environmentally acquired vitamin D equivalent to 20-50 microg (800-2000 IU)/d. The assembled data from many vitamin D supplementation studies reveal a curve for vitamin D dose versus serum 25-hydroxyvitamin D [25(OH)D] response that is surprisingly flat up to 250 microg (10000 IU) vitamin D/d. To ensure that serum 25(OH)D concentrations exceed 100 nmol/L, a total vitamin D supply of 100 microg (4000 IU)/d is required. Except in those with conditions causing hypersensitivity, there is no evidence of adverse effects with serum 25(OH)D concentrations <140 nmol/L, which require a total vitamin D supply of 250 microg (10000 IU)/d to attain. Published cases of vitamin D toxicity with hypercalcemia, for which the 25(OH)D concentration and vitamin D dose are known, all involve intake of > or = 1000 microg (40000 IU)/d. Because vitamin D is potentially toxic, intake of >25 microg (1000 IU)/d has been avoided even though the weight of evidence shows that the currently accepted, no observed adverse effect limit of 50 microg (2000 IU)/d is too low by at least 5-fold.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Mount Sinai Hospital, Ontario, Canada. rvieth@mtsinai.on.ca
authors.forename: R
authors.initials: R
authors.lastname: Vieth
mesh_terms: D000367:Age Factors; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D006801:Humans; D006961:Hyperparathyroidism / Q000209:etiology; D019055:No-Observed-Adverse-Effect Level; D009747:Nutritional Physiological Phenomena; D009751:Nutritional Requirements; D010018:Osteomalacia / Q000517:prevention & control; D013472:Sunlight; D014807:Vitamin D / Q000008:administration & dosage* / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000097:blood / Q000592:standards*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D