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Cranney A, Horsley T, O'Donnell S, et al. Effectiveness and Safety of Vitamin D in Relation to Bone Health. Rockville (MD): Agency for Healthcare Research and Quality (US); 2007 Aug. (Evidence Reports/Technology Assessments, No. 158.)

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

Cover of Effectiveness and Safety of Vitamin D in Relation to Bone Health

Effectiveness and Safety of Vitamin D in Relation to Bone Health.

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Key Terms

Dietary Reference Intakes4

Adequate Intake (AI) - an adequate intake is based on observed estimates of average nutrient intake by a group of healthy people. It is expected to meet or exceed the amount needed to maintain a defined nutritional state or criterion of adequacy in essentially all members of a specific healthy population.

For infants 0 - six months, the AI is based on the estimated daily mean intake supplied by human milk for healthy full-term infants who are exclusively breast-fed. For other age groups, the AI is the vitamin D intake value that appears to be needed to maintain, in a defined group of individuals, serum 25(OH)D at a concentration below which e.g., vitamin D deficiency rickets or osteomalacia occurs. The AI assumes no vitamin D is available from sun-mediated cutaneous synthesis.

Estimated Average Requirement (EAR) - the nutrient intake value that is estimated to meet the requirement defined by a specified indicator of adequacy in 50 percent of the individuals in a life stage and gender group. This is used to set a Recommended Daily Allowance (RDA). An EAR could not be established by the IOM in its 1997 Daily Reference Intakes for vitamin D due to insufficient data.

Recommended Dietary allowance (RDA) - the average daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97 – 98 percent) individuals in a life stage and gender group. An EAR is the basis for setting the RDA. In the absence of sufficient data for an EAR, an AI is established.

Tolerable Upper Intake Limit - the highest level of daily intake that is likely to pose no risks of adverse health effects to almost all individuals in the general popultion.

Current Adequate Reference Intakes (IOM, 1997)4

Age groupAdequate Intakes
infants 0 – 13 y200 IU (5 ug/day)
children 14 – 18 y200 IU (5 ug/day)
adults 19 – 50 y200 IU (5 ug/day)
pregnant or lactating women (14 – 50 y)200 IU (5 ug/day)
adults 51 – 70 y400 IU (5 ug/day)
adults > 70 y600 IU (10 ug/day)

Vitamin D Terms

Provitamin D3 7 dehydrocholesterol (7-DHC)
Previtamin D3 Synthesized in the skin from 7-dehydrocholesterol
CholecalciferolVitamin D3. Synthesized in the skin in response to sunlight of wavelengths 290 – 320 nm (UV-B); synthesis is initiated by the photoconversion of provitamin D3 to previtamin D3.
Calcidiol25 hydroxycholecalciferol or calcifediol (25(OH)D3) - hydroxylated in the liver as the first step in the conversion of vitamin D3 to the active form
Calcitriol1,25 dihydoxyvitamin D3 (1,25-(OH)2D3), the form of vitamin D3 that is biologically active; produced by the hydroxylation of 25(OH)D in the kidney or at extrarenal sites.
ErgocalciferolVitamin D2, present in some naturally occuring dietary sources and in some supplements.

Conversion Factors

1 ng/mL of 25(OH)D = 2.5 nmol/L

1 ug of vitamin D = 40 IU

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