Invited Symposium: Regulators of Skeletal Growth and Integrity in Health and Disease



Synthesis and Metabolism of Vitamin D

Recommended Adequate Dietary Intake of Vitamin D




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How Much Vitamin D is Enough?

Holick, MF. (Department of Medicine, Boston University Medical Center, Boston, MA, USA)

Contact Person: Michael F. Holick (mfholick@bu.edu)


Vitamin D is neither a vitamin nor a nutrient if adequate exposure to sunlight is available. Vitamin D is critically important for regulating the efficiency of intestinal calcium absorption in order to maintain intra- and extracellular calcium concentrations for a wide variety of metabolic processes that are associated with neuro-muscular function and skeletal health. Exposure of the skin to sunlight results in the production of previtamin D3, which quickly transforms to vitamin D3. Vitamin D3 enters the circulation and is metabolized in the liver and kidney to 1,25-dihydroxyvitamin D3. Vitamin D-deficiency causes rickets in children, exacerbates osteoporosis and causes osteomalacia in adults. Very few foods naturally contain vitamin D. Fatty fish such as salmon, cod liver oil, vitamin D-fortified milk and cereals and multivitamin supplements are the major sources of vitamin D. New recommendations for dietary reference intakes by the Food and Nutrition Board for vitamin D include adequate intakes of 200 IU, 400 IU, and 600 IU/d of vitamin D for newborns-49 yrs, 50-70 yrs, and 71+ yrs, respectively. The new, safe, tolerable upper intake levels were set at 1000 and 2000 IU/day for 0-12 months and 1 year, respectively. Treatment of vitamin D- deficiency in adults can be corrected by giving them 50,000 units of vitamin D once a week for 8 weeks followed by a multivitamin containing 400 IU/day.

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Presentation Number SAholick,0835
Keywords: vitamin D, rickets, osteomalacia, bone, calcium

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Holick, MF.; (1998). How Much Vitamin D is Enough?. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/atkinson/holick0835/index.html
© 1998 Author(s) Hold Copyright