Vitamin D insufficiency

[Neon Beach]

Vitamin D insufficiency: no recommended dietary allowance exists for this nutrient

Reinhold Vieth and Donald Fraser
Dr. Vieth is Associate Professor, Department of Laboratory Medicine and Pathobiology, University of Toronto, and Director of the Bone and Mineral Laboratory, Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Ont. Dr. Fraser is Professor Emeritus, Departments of Paediatrics and Physiology, University of Toronto, and Honourary Physician, the Hospital for Sick Children, Toronto, Ont. He was a member of the Committee on Nutrition, American Academy of Pediatrics, the reports of which formed the basis of earlier vitamin D recommendations for infants and adults.

Correspondence to: Dr. Reinhold Vieth, Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, 600 University Ave., Toronto ON M5G 1X5; fax 416 586-8628; rvieth@mtsinai.on.ca

Rickets, a defect in bone growth during infancy and childhood, was first characterized in 1650. Although cod-liver oil was used as a folk remedy in northern Europe starting in the late 1700s, it was not until 1922 that the medical community realized that something in it prevented and cured rickets.1,2 As recently as 4 decades ago, physicians assumed that vitamin D nutrition was adequate if people exhibited no clinical or radiographic signs of rickets.3,4 Osteomalacia, the adult counterpart of rickets, was rarely seen, and it was assumed that adults require no more, and usually less, vitamin D than infants do.4 It was also assumed that the vitamin D generated in the skin, vitamin D3, was functionally equivalent to a different molecule, vitamin D2, generated from lipids in yeast.3,4

Physicians have been able to quantify vitamin D nutritional status in their patients since the 1970s, by measuring the serum concentration of 25(OH)D. A low concentration of 25(OH)D causes a form of secondary hyperparathyroidism, which is thought to accelerate bone loss.5 Unfortunately, the practical advice about how to deal with vitamin D nutrition in adults has always been vague and, we think, misleading.


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