Efficacy of high-dose vitamin D supplements for elite athletes

Daniel J. Owens, Jonathan C. Y. Tang, Warren J. Bradley, S. Andy Sparks, William D. Fraser, James P. Morton, Graeme L. Close

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Purpose: Supplementation with dietary forms of vitamin D is commonplace in clinical medicine, elite athletic cohorts and the general population, yet the response of all major vitamin D metabolites to high doses of vitamin D is poorly characterized. We aimed to identify the responses of all major vitamin D metabolites to moderate and high dose supplemental vitamin D3.

Methods: A repeated measures design was implemented in which 46 elite professional European athletes were block randomized based on their basal 25[OH]D concentration into two treatment groups. Athletes received either 35,000 or 70,000 IU.week-1 vitamin D3 for 12 weeks and 42 athletes completed the trial. Blood samples were collected over 18 weeks to monitor the response to supplementation and withdrawal from supplementation.

Results: Both doses led to significant increases in serum 25[OH]D and 1,25[OH]2D3. 70,000 IU.week-1 also resulted in a significant increase of the metabolite 24,25[OH]¬2D at weeks 6 and 12 that persisted following supplementation withdrawal at week 18, despite a marked decrease in 1,25[OH]2D3. Intact PTH was decreased in both groups by week 6 and remained suppressed throughout the trial.

Conclusions: High dose vitamin D3 supplementation (70,000 IU.week-1) may be detrimental for its intended purposes due to increased 24,25[OH]2D production. Rapid withdrawal from high dose supplementation may inhibit the bioactivity of 1,25[OH]2D3 as a consequence of sustained increases in 24,25[OH]2D that persist as 25[OH]D and 1,25[OH]2D concentrations decrease. These data imply that lower doses of vitamin D3 ingested frequently may be most appropriate and gradual withdrawal from supplementation as opposed to rapid withdrawal may be favorable.
Original languageEnglish
Pages (from-to)349–356
Number of pages8
JournalMedicine and Science in Sports and Exercise
Issue number2
Early online date13 Oct 2016
Publication statusPublished - Feb 2017


  • 25-hydroxyvitamin D
  • 24,25-dihydroxyvitamin D
  • 1,25-dihydroxyvitamin D3
  • parathyroid hormone
  • vitamin D

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