Calcidiol may be 5X more effective than Vitamin D3 – June 2012

Relative effectiveness of oral 25-hydroxyvitamin D3 and vitamin D3 in raising wintertime serum 25-hydroxyvitamin D in older adults

Kevin D Cashman, Kelly M Seamans, Alice J Lucey, Elisabeth Stöcklin, Peter Weber, Mairead Kiely, and Tom R Hill
Am J Clin Nutr June 2012 ajcn.031427

  • 1 From the School of Food and Nutritional Sciences (KDC, KMS, AJL, MK, and TRH) and the Department of Medicine (KDC), University College Cork, Cork, Ireland, and DSM Nutritional Products Ltd, Kaiseraugst, Switzerland (ES and PW).
  • 2 Supported by the Irish Department of Agriculture, Food and the Marine under its Food Institutional Research Measure (grants to KDC and MK). DSM Nutritional Products Ltd supplied the vitamin D3 and 25-hydroxyvitamin D3 for supplements.
  • 3 Present address for TRH: School of Agriculture, Food and Rural Development and Human Nutrition Research Centre, Newcastle University, Newcastle-Upon-Tyne, United Kingdom.
  • 4 Address correspondence to KD Cashman, School of Food and Nutritional Sciences and Department of Medicine, University College Cork, Cork, Ireland. E-mail:

Background: The relative potency of 25-hydroxyvitamin D3 to vitamin D3 needs to be better defined so that food-composition tables can better reflect the true vitamin D nutritive value of certain foods.

Objective: We performed a randomized, controlled intervention study in apparently healthy, free-living adults to investigate whether the intake of 25-hydroxyvitamin D3 is 5 times more potent in raising serum 25-hydroxyvitamin D [25(OH)D] during winter compared with an equivalent amount of vitamin D3.

Design: A randomized, placebo-controlled, double-blind intervention study was conducted in adults aged ?50 y (n = 56) who consumed a placebo, 20 ?g vitamin D3, or 7 or 20 ?g 25-hydroxyvitamin D3 daily throughout 10 wk of winter. Serum 25(OH)D was measured by using an enzyme-linked immunoassay, and serum albumin–corrected calcium (S-Ca) was assessed colorimetrically at the baseline, midpoint, and endpoint of the study.

Results: The mean (±SD) increases (per microgram of vitamin D compound) in serum 25(OH)D concentrations over baseline after 10 wk of supplementation were 0.96 ± 0.62, 4.02 ± 1.27, and 4.77 ± 1.04 nmol ? L?1 ? ?g intake?1 for the 20-?g vitamin D3/d and 7- and 20-?g 25-hydroxyvitamin D3/d groups, respectively. A comparison of the 7- and 20-?g 25-hydroxyvitamin D3/d groups with the 20-?g vitamin D3/d group yielded conversion factors of 4.2 and 5, respectively. There was no effect of treatment on S-Ca concentrations and no incidence of hypercalcemia (S-Ca >2.6 nmol/L).

Conclusions: Each microgram of orally consumed 25-hydroxyvitamin D3 was about 5 times more effective in raising serum 25(OH)D in older adults in winter than an equivalent amount of vitamin D3. This conversion factor could be used in food-compositional tables for relevant foods. This study was registered at as NCT01398202.

Received November 24, 2011, Accepted February 22, 2012.

Questions/observations by VitaminDWiki

  • Is calcidiol >5X as expensive?
  • Is calcidiol only available via prescription?
  • The 800 IU of vitamin D resulted in only a tiny increase in blood levels
    800 IU often is too small to increase blood levels in 10 weeks – especially if deficient
    Might have had very different results if
       larger amounts of D3 were given
       longer time to restock the vitamin D levels (seniors often need 20-100 weeks, not just 10)
       patients were not deficient or had been repleted before the RCT.
  • Wonder how many of the seniors had poor gut or poor liver function

See also VitaminDWiki

Getting Vitamin D into your body has the following chart

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