Exp Biol Med (Maywood). 2010 Jul 28.
Norman AW, Bouillon R.
Department of Biochemistry and Division of Biomedical Sciences, University of California, Riverside, CA 92521, USA.
Historically vitamin D is known to be essential for normal bone growth and quality, and thus appropriate dietary vitamin D supplementation can eliminate vitamin D deficiency childhood rickets and adult osteomalacia. In spite of many government and medical associations' worldwide guidelines for the reference daily intake (RDI) of vitamin D, scientists and nutritionists from many countries agree that at present about half of elderly North Americans and Western Europeans and probably also of the rest of the world are not receiving enough vitamin D to maintain healthy bone.
In addition, over the past decade there has been a dramatic increase in our understanding of the many biological actions that result from vitamin D acting through its daughter steroid hormone, 1alpha,25-dihydroxyvitamin D(3) 1alpha,25(OH)(2)D(3) in collaboration with its cognate vitamin D receptor (VDR). Consequently, evidence has accumulated that beside intestine and bone, there are five additional physiological systems where the VDR with 1alpha,25(OH)(2)D generates biological responses. These include the immune system (both the innate and adaptive), pancreas and metabolic homeostasis, heart-cardiovascular, muscle and brain systems as well as the control of the cell cycle, and thus of the disease process of cancer. Acting through the VDR, 1alpha,25(OH)(2)D(3) can produce a wide array of favorable biological effects that collectively are projected to contribute to the improvement of human health. Responsible medicine demands that worldwide vitamin D nutritional guidelines reflect current scientific knowledge about vitamin D's spectrum of activities.
Thus, worldwide vitamin D nutritional policy is now at a crossroads. This paper presents several proposed policy changes with regard to the amount of vitamin D daily intake that if implemented will maximize vitamin D's contribution to reducing the frequency of many diseases, which would then increase the quality and longevity of life and significantly reduce the cost of medical care worldwide. PMID: 20667908
Toward the end of the article the author describes the Dilemma of trying to establish a single RDA for everyone.
He examines 4 solutions - all of which have positive and negative aspects.
(i) No change in present situation:
(ii) Strict implementation of present guidelines for vitamin D intake:
(iii) Implementation of an intermediate approach:
(iv) Implementation of an interventionist policy: If the vitamin D dietary intake were increased to 2000 IU/d ...
We doubt that a single RDA, even if it compensates for age and pregnancy, will be unable to cover the huge variation in vitamin D needs due to skin color, latitude, obesity, etc.