The Role of the Parent Compound Vitamin D with Respect to Metabolism and Function: Why Clinical Dose Intervals can affect Clinical Outcomes.
J Clin Endocrinol Metab. 2013 Oct 8.
Hollis BW, Wagner CL.
Division of Neonatology, Medical University of S Carolina Children's Hospital, Department of Pediatrics, Charleston, SC.
Context:There is no doubt that vitamin D must be activated to the hormonal form 1,25-dihydroxy vitamin D [1,25(OH)2D] to achieve full biological activity or that many tissues participate in this activation process-be it endocrine or autocrine. We believe that not only is 25-hydroxyvitamin D [25(OH)D] important to tissue delivery for this activation process, but that intact vitamin D also has a pivotal role in this process.
Objective:In this review, evidence on the vitamin D endocrine/autocrine system is presented and discussed in relation to vitamin D-binding protein (VDBP) affinity, circulating half-lives and enzymatic transformations of vitamin D metabolites, and how these affect biological action in any given tissue.
Conclusions:Circulating vitamin D, the parent compound, likely plays an important physiological role with respect to the vitamin D endocrine/autocrine system, as a substrate in many tissues, not originally thought to be important.
Based on emerging data from the laboratory, clinical trials, and data on circulating 25(OH)D amassed during many decades, it is likely that for the optimal functioning of these systems, significant vitamin D should be available, on a daily basis, to ensure stable circulating concentrations, implying that variation in vitamin D dosing schedules could have profound effects on the outcomes of clinical trials because of the short circulating half-life of intact vitamin D.
Henry Lahore of VitaminDWiki discussed this with researchers at Vitamin D Workshop in June 2014
- Yes, should take vitamin D daily if not taking enough vitamin D to build up stores in the body.
- That is, when taking < about 2,500 IU average daily there is no reserve in the body, so the vitamin D content on the breast milk will go up every time the mother gets a supplement
- However, when taking > 4,000 IU average daily a reserve will be built up in the mother's body, so thevitamin D in breast milk will not vary nearly as much.
- Thus it should be fine to take a 50,000 IU capsule of vitamin D once every two weeks while breastfeeding.
- Vitamin D once every two weeks is OK, daily is nice but not required – Aug 2014
- People reported taking pills, pills were all gone, but occasionally bottles were not opened – Dec 2015
- Take vitamin D3 daily or weekly which has the following notional chart for < 30ng