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Vitamin
D supplementation, 25-hydroxyvitamin D concentrations, and safety
Vieth
R
Department
of Laboratory Medicine and Pathobiology, University of Toronto, Mount Sinai
Hospital, Ontario, Canada.
rvieth@mtsinai.on.ca
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.
PMID:
10232622 [PubMed - indexed for MEDLINE]
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